# Sticky  Cross-Spectrum Microphone Calibration Service - USA



## Sonnie

We are happy to announce and recommend Cross-Spectrum Labs for microphone calibration in the U.S. ... particularly the Behringer ECM8000 and Galaxy CM-140. Of course, they will also calibrate other microphones as well.

*Cross·Spectrum Labs
P.O. Box 90842
Springfield, MA 01139*

I have personally spoken with Herb Singleton, founder of Cross-Spectrum, and he as agreed to calibrate these units 10Hz to 20KHz provided you specify you would like calibration to 10Hz. The charge is $55.00 and includes the cost of return shipping via USPS for customers in the continental United States.. 

Cross-Spectrum will use the pressure method to calibrate the low frequency response and the quasi-anechoic free-field on-axis method to calibrate the upper frequency response. The pressure method is one of the most accurate methods of measuring the frequency response of a microphone, however baffle diffraction must be accounted for when using this method. Generally mic manufacturers will provide the variance to offset the baffle diffraction. Unfortunately, Behringer nor Galaxy offers these variance corrections. Therefore, the free-field method of measuring the upper frequencies will be more accurate for these units. These combined calibration methods will give us the best calibration file for the ECM8000 and CM-140 mics. This is one of the first labs we have found that will calibrate the CM-140 SPL Meter microphone.

Cross-Spectrum also offers calibrated Behringer ECM-8000 microphones for sale. The cost is $100 + shipping. Please see their Behringer page for more information. 

Herb will be joining us here at the Shack and has agreed to answer any questions anyone may have. Please check out their site before asking questions... you may very well find your answer. If you do not find the answer you are looking for, you may post a question here in this thread and Herb will do his best to get you an answer. Remember he is busy in the lab and does not monitor this forum 24/7, so please be patient... or you are more than happy to contact him by telephone (see their Contact Us page).

Remember, if you are wanting your mic calibrated to 10Hz, you must include a note requesting same, otherwise the calibration may only be to 20Hz.

We appreciate Herb's willingness to work with us in providing this service to our members here at the Shack.


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## Anechoic

*Re: Cross-Spectrum Microphone Calibration Service*

Hi all,

Herb here. Sonnie covered most of the bases, but I wanted to stick my head in here and let you know that I am available to answer any questions. I will be here from time to time to check up on things, and I have subscribed to this thread, but it's likely that I may miss questions so feel free to email me or call my cell phone: 617-901-7472. (If I don't answer, *leave a message* and I promise I'll return your call. If you call multiple times and never leave a message, I guarantee I'll never answer it.) Also feel free to post any responses I email to you here for others to read.

I do want to mention that there are lots of things that go into mic cals, so I try to be as transparent as possible with respect to my reference equipment and techniques so you can evaluate the strengths and weaknesses for yourself. The one thing that I have learned from doing this is that when you look at lab to lab or manufacturer to manufacturer _everyone_ seems to do it just a little differently - in fact I've learned how some of the Big Boys do it and it's funny how ghetto some of their methods are. I am on the AES working group SC-04-04 (Working Group on Microphone Measurement and Characterization) which is trying to update an old IEC standard on mic measurements. Hopefully this effort will result in more standardization in free-field microphone calibrations.

If you are interested in the cal service, please drop me an email and I'll give you the shipping address - I don't like to publish the shipping address because I've moved three times since I've started offering the service and my previous shipping addresses have wound up in various corners of the internet resulting in people shipping mics to my old addresses without letting me know. I generally try to turn them around in 48-hours but my normal duties require a lot of travel so I may not always get to it. I will let you know ahead of time if my schedule is tight. 

Sonnie mentioned that many users here want 10 Hz to 24kHz cals. I'm happy to do that, but please indicate that you want that frequency range, otherwise I'm going to default to my normal 20 Hz to 20kHz cals.

I do sell pre-calibrated ECM8000, but lately it seems that everyone and their uncle wants one and I'm having a real hard time keeping up with the orders. Again, email or call ahead 

Also, if anyone is interested in stepping up to professional measurement microphones (Bruel & Kjaer, GRAS, BSWA, ACO Pacific, Larson-Davis, etc), I have a lot of experience with them (in fact I own B&K, ACO, BSWA and Rionmics) so again feel free to ask.

Good luck all.


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## brucek

*Re: Cross-Spectrum Microphone Calibration Service*

We've recently been discussing the proper orientation for a measurement mic such as the ECM8000 in this thread and have found a difference between vertical and horizontal orientation. 

I understand that your calibrations are for a vertical orientation (EDIT incorrect - the default calibration is horizontal on-axis), but I wonder if the calibration is still accurate when measuring near-field (<= 12") or even at close diffuse soundfield distances such as 50". I did some tests of my tweeter in my loudspeakers here, but still used the horizontal orientation.

Can you comment on taking measurements at a listening position compared to near-field, with respect to mic orientation and a single calibration file.

brucek


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## Ricci

*Re: Cross-Spectrum Microphone Calibration Service*

Welcome Herb. It's great to have someone with your experience around. You'll most likely be hearing from me soon about a mic calibration.

Can you calibrate mics even lower than 10hz? Could you do 5 or even 3hz?


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## Anechoic

*Re: Cross-Spectrum Microphone Calibration Service*

I have to head out for the day, but I will address the questions as soon as I can.


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## Anechoic

*Re: Cross-Spectrum Microphone Calibration Service*

Okay, it took me a while, but I'm back.



> I understand that your calibrations are for a vertical orientation, but I wonder if the calibration is still accurate when measuring near-field (<= 12") or even at close diffuse soundfield distances such as 50". I did some tests of my tweeter in my loudspeakers here, but still used the horizontal orientation.


Just to be clear - my measurements results give the on-axis mic frequency response; that is, the mic diaphragm is facing the sound source.



> Can you comment on taking measurements at a listening position compared to near-field, with respect to mic orientation and a single calibration file.


Well there's really no simple answer. I skimmed the thread you linked to and for the most part, the exposition there is on the right track. The important thing is that at the higher frequencies, the orientation of the microphone does matter. At the highest frequencies, the wavelength becomes comparable to the size of the microphone and therefore the mic does have an influence on the soundfield. For a 1/2-inch mic, the effects really start around 1 kHz but become noticeable around 2-4 kHz. A 1/4-inch or 3/8-inch mic (like the dbx RTA-M) gives you another octave or so before the effects become noticeable.

You shouldn't see any proximity affects in the high frequencies with condenser mics. You also shouldn't see any proximity effects in the low freqs with condenser mics like the ECM8000 - however the most recent runs of ECM8000 come with a chart that claims there is one, but I haven't observed it (although to be honest, I haven't investigated it all that much.) But since Behringer has never released a freq response curve for the ECM8000 that has agreed with what I and others have measured, I'm not going to put too much stock into it.

Since the response of most measurement mics will depend on the orientation, what to do? Well, if you're trying to measure the freq response of a particular source, measure with the mic pointed at the source (which will minimize the effect of the mic body) and apply your calibration curve to correct the response. If you're doing a room measurement for DRC or other purposes (STC or RT60 measurements) what you really should be using a diffuse field microphone (which pretty much no one does) or you should measure at various locations with a free-field mic at various orientations (as recommended in ASTM E336), and then average the responses together. Of course most of us don't have the time and/or patience to do that, so when I do room measurements, I put the mic in random incidence position (mic facing the source and angled 70-80 degrees with respect to the floor).

Of course the catch is that typically the cal files you have are for one orientation. If you really care that much about it, you can get polar measurements of the mic (which I can measure for additional cost) and apply the specific cal file, or just do some trial and error and see what works for you. As I wrote above, in practice I use random-incidence positioning and apply the cal file I get from my 3rd party cal lab and I've always gotten reasonable results.

If your measuring loudspeaker frequency response, you shouldn't have a diffuse field, you should be gating the results so that you only have the direct sound. If you do that, the cal file should apply no matter the distance (where the distance is limited to how long your gate is of course).




> Can you calibrate mics even lower than 10hz? Could you do 5 or even 3hz?


Sonnie mentioned that a bunch of people here where interested in getting down below 10 Hz. I have put together a pressure field jig and I can get down to 5 Hz, but that's as low as I can go. Below that, you start getting into regions where ambient air pressures have an effect. If I want to get much below 5 Hz, I either need to invest in an electrostatic actuator or build an air-tight pressure chamber, either of which would be a substantial investment on my part and since mic measurements are a tiny part of what I do, it's not worth it at this point. However I may get lucky on eBay, so stay tuned.


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## brucek

*Re: Cross-Spectrum Microphone Calibration Service*

Thanks for your detailed answer.

I guess our recommendations for measuring loudspeakers (near field) using a horizontal on-axis orientation, combined with proper gating, are correct.

Where we differ from your recommendations, is when measuring a room at the listening position. We have been advising members to use a vertical orientation for their ECM8000 mics, so as to take in all reflections equally, since the ECM8000 is an omni-directional mic. If I understand correctly, you're advising to face the source using an almost horizontal mic position (70-80deg). Since your calibrations are for on-axis, facing the source orientation, I guess that would make sense. 

Do you offer calibrations for both vertical and horizontal positions of the mic?

brucek


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## Anechoic

*Re: Cross-Spectrum Microphone Calibration Service*



> If I understand correctly, you're advising to face the source using an almost horizontal mic position (70-80deg).


No, I'm saying use an almost-vertical orientation where "vertical" is 90 degrees and I rotate the mic toward the floor by 10-20 degrees (if "vertical" is 12-o'clock, I measure with the mic pointing at ~1 or 2-o'clock). There will be some error since the cal file is based on an horizontal alignment, but even with the "correct" cal file there will be some error at the highest frequencies regardless because you're using a freefield mic for what is essentially a diffuse-field measurement. But it's not something that causes me to lose a lot of sleep although I'm sure others feel differently. 



> Do you offer calibrations for both vertical and horizontal positions of the mic?


I can perform additional measurements at 45 and/or 90 degree angles for free, but any more than that (or full-blown polar measurements) is extra.


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## brucek

*Re: Cross-Spectrum Microphone Calibration Service*



> I'm saying use an almost-vertical orientation where "vertical" is 90 degrees and I rotate the mic toward the floor by 10-20 degrees


Ahh OK. I usually consider vertical to mean 0 degrees (straight up and down), and so your 70-80 degrees meant a near horizontal position to me. But, I get it now.

So we're not far apart on this then. I usually recommend vertical, and you're recommending vertical with a slight tilt (10-20deg) toward the mains speakers at the listening position. Seems fair. And again, since this is for home use for most of us, a few dB isn't going to cause any problems either way, since most of us are using a generic calibration file...

brucek


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## Ricci

*Re: Cross-Spectrum Microphone Calibration Service*

Thanks for the detailed answers. I have an additional one. How much would a an ECM calibrated down to 5hz be with an additional 45 and 90 degree measurement? I'm most likely going to get on the waiting list for one.


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## Anechoic

*Re: Cross-Spectrum Microphone Calibration Service*



> And again, since this is for home use for most of us, a few dB isn't going to cause any problems either way, since most of us are using a generic calibration file...


Yep. When it comes to acoustical measurements the reality is that there are always limitations that we have to live with. For example, if you really want to know what's going on a 20 kHz (say, for a speaker measurement) you really need to be using a 1/4-inch mic, since a 1/2-inch mic is so big relative to the wavelength so that you get diffraction effects and the diaphragm doesn't necessarily act like a piston (there's a reason why IEC and ANSI standards for Type 1 mics go to -infinity above 16 kHz). If you're careful, you can get a "good enough" number up that high but it's not going to be anywhere near as accurate as what you're getting in the 100 Hz - 3 kHz range. 



> How much would a an ECM calibrated down to 5hz be with an additional 45 and 90 degree measurement? I'm most likely going to get on the waiting list for one.


I won't charge extra for that, but you'll have to ask for it when you order it. And yes, there is a waiting list - it's been really crazy lately, everytime I get some in stock, they immediately go out again.


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## redliner

*Re: Cross-Spectrum Microphone Calibration Service*

What's the turnaround time once you're on the waiting list?


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## Anechoic

*Re: Cross-Spectrum Microphone Calibration Service*



redliner said:


> What's the turnaround time once you're on the waiting list?


It really depends on where you are on the queue and my schedule. Right now I have no back orders and zero stock (which should get refreshed early next week) so the first few orders I get now should go out no later than March 2.


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## Dennis H

*Re: Cross-Spectrum Microphone Calibration Service*

Hi Herb,

Good to see you posting here. Do you have any guess about the high and low end roll-offs of the Behringer? Say X dB/oct at Y Hz? With a 96K sound card and a 128K FFT, you could be generating measurement files covering .7-48K Hz. It would be nice to have some non-zero numbers in the cal file at those extremes, even if they were just a wild guess, so you didn't have your CAD software assuming there was a sudden big jump in the response. Seems like that could lead to phase errors in your crossover design.


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## Anechoic

*Re: Cross-Spectrum Microphone Calibration Service*

The ECM8000s have so much unit to unit variation (see here) that I'm not comfortable giving generalized numbers - well other than +/- 15 from 20Hz to 20kHz .

As for the extremes, yes it is possible with a long FFT and wideband sound card to give a wide frequency response, but acoustically it's very difficult to generate reliable test data at those extremes. I could give numbers at those frequencies, but they would be meaningless.


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## lcaillo

*Re: Cross-Spectrum Microphone Calibration Service*

Amen to that!


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## Dennis H

*Re: Cross-Spectrum Microphone Calibration Service*



Anechoic said:


> The ECM8000s have so much unit to unit variation that I'm not comfortable giving generalized numbers - well other than +/- 15 from 20Hz to 20kHz .
> 
> As for the extremes, yes it is possible with a long FFT and wideband sound card to give a wide frequency response, but acoustically it's very difficult to generate reliable test data at those extremes. I could give numbers at those frequencies, but they would be meaningless.


 Okay, forget the Behringer. Generally speaking, what is the slope of the roll-off of generic condenser mics on the high and low end? 2nd order? Steeper? I'm just trying to learn how these mics work.


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## Anechoic

*Re: Cross-Spectrum Microphone Calibration Service*



Dennis H said:


> I'm just trying to learn how these mics work.


So am I. 

The short answer is "it depends on how the microphone and microphone pre-amp are designed." I have to head out for the day, but I'll give a more detailed explanation later this evening.


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## Dennis H

*Re: Cross-Spectrum Microphone Calibration Service*

Thanks, Herb. To keep things simple, could we start with the response of a plain old electret capsule with no extra circuits? Most software takes 2-channel measurements these days so the response of the preamp gets subtracted out.


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## Anechoic

*Re: Cross-Spectrum Microphone Calibration Service*



Dennis H said:


> Thanks, Herb. To keep things simple, could we start with the response of a plain old electret capsule with no extra circuits? Most software takes 2-channel measurements these days so the response of the preamp gets subtracted out.



Just to make sure we're all on the same page: when I talk about the capsule, I'm refering to the "tip" of the microphone that has the microphone diaphragm, blackplate, isolator and electrical terminals(and grill if applicable). When I talk about the pre-amp, I'm not referring to the phantom power supply or the sound-card interface, I'm talking about the electronics that convert the varying charge into an output voltage and steps up the voltage. In the parlance of my reference equipment, this is the mic capsule, and this/this is the pre-amp. In mics like the dbx RTA-M or ECM8000, the unit contains both the mic and the preamp (which gets plugged into another pre-amp to provide phantom power and bump up the output more).

A condenser mic can go down to DC, in which case you could use it measure atmospheric pressure. In practice, the rear of the diaphragm is usually vented to prevent the diaphragm from breaking during sudden pressure changes or exposure to very high SPLs. This vent creates a low-frequency roll-off which limits the low-frequency performance of the microphone. The vent hole and the volume of air behind the diaphragm is a small resonant chamber; the size of these parameters determine the roll-off, so you need to know those parameters to predict the roll-off of any particular microphone.

The theoretical roll-off on the high frequencies for condenser mics (normal incidence) is 12 dB per octave if you only consider an undamped system. However, at mid-audio frequencies (8-13kHz depending on a variety of factors including diaphragm diameter) there is a resonance that manufacturers try to damp out though adjusting the vent sizes, grill design, diaphragm tension and diaphragm mass. This damping can change the slope of the high-frequency roll-off depending on the proximity of the resonance to the high-frequency limit of the mic. So if you want to use a number for the high-frequency rolloff, use 12dB/octave but it's going to be a wild guess at best.

We also have to account for the performance of the pre-amp response. Manufacturers may try to use the electronics to tweak the frequency response of the capsule, which may also have an effect on the rolloff. 

HTH.


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## bxxk

*Re: Cross-Spectrum Microphone Calibration Service*

Hi Herb, 

I've built some mics before, including an ambisonic tetrahedral mic, and used a B&K reference mic to manage the calibration. But I would not mind my own for my home DRC work... I'm sure I'm not alone in wondering what you would recommend in various price ranges for a cheap or inexpensive reference mic.

The reason I'm asking is because the ECM8000 is not all that good (eg the bass roll off, which is not in the original Panasonic WM51a capsules, so is possibly in their preamp), even for the price - I believe the similar NADY is better and I've seen home made units which are better. Whatever mic is used will still need calibration, but using a better (flatter / quieter) mic to start with is usually a good idea.

Many thanks for your input, it is much appreciated.
BK


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## Anechoic

*Re: Cross-Spectrum Microphone Calibration Service*



bxxk said:


> Hi Herb,
> 
> I've built some mics before, including an ambisonic tetrahedral mic, and used a B&K reference mic to manage the calibration. But I would not mind my own for my home DRC work... I'm sure I'm not alone in wondering what you would recommend in various price ranges for a cheap or inexpensive reference mic.


It's kind of a broad question that's difficult to answer, but I'll try.

In the same (rough) price range as the ECM8000 I've measured the Nady CM 100 and the dbx RTA-M. The Nady is flatter to 20 kHz although I didn't look much lower. The RTA-M rolls off a bit above 20 Hz. 

If you're willing to spend a couple of hundred dollars, the Josephson and Earthworks lines are great mics for the price, but pricewise are geared for the serious enthusiast. The Beyerdynamic MM 1 has a great reputation and can sometimes be found for under $200, but I've never personally handled one. There's the APEX220 which falls into the ECM8000 price range and may or may not be a rebadged RTA-M.

One microphone that I really like is the Radio Shack lapel microphone. They're cheap, but they are amazingly flat up to 20 kHz and much more consistent from unit to unit. The downside is that the noise floor is pretty high (around 60 dBA IIRC) which limits its use for low SPL testing. You also have to find a way to mount it such that the mounting doesn't muddy up the signal. Caveat: it's been several years since I last measured one so it's entirely possible that there has been a revision and the mic is now.


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## Dennis H

*Re: Cross-Spectrum Microphone Calibration Service*

I think the Behringer and the Nady are both OEM'd from Superlux in China -- probably the same mic with a different label. They seem to have lost their flat response when Panasonic discontinued the WM-60 and everyone switched to the WM-61. I thought it was a Superlux problem but I recently read a paper where someone built 8 mics using the WM-61, 4 with the stock wiring and 4 with the 'Linkwitz mod'. They all had the 10K hump although the ones with the mod didn't hump quite as high. The ones with the mod also had lower distortion at high SPL.

Herb, the Panasonic electret capsules don't really require a preamp like you describe for a traditional condenser mic. They work fine with just a battery and a resistor as long as they are feeding a fairly high impedance preamp or sound card. Superlux is including more of a preamp built in to make them compatible with a pro mic preamp with low impedance and 48V.

I was looking at some measured 5-48K curves for the Behringer and it looks like the tails are more like 24dB/oct. The tails don't really matter for someone measuring a room but they could make a difference for someone designing a crossover because of errors in the calculated phase using a Hilbert transform. As an experiment, I built a fake cal file extending down to 1Hz and ran a Hilbert transform to get the phase. Then I truncated the file to 20Hz and ran the HBT again. The phase error at 20Hz was about 70 degrees with the truncated file.


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## Anechoic

*Re: Cross-Spectrum Microphone Calibration Service*



Dennis H said:


> I think the Behringer and the Nady are both OEM'd from Superlux in China -- probably the same mic with a different label.


There was a discussion a few years back on Usenet (Google groups search is completely fubar'd right now so I can't find it) where there was some dispute over that - I think the mic element was probably the same but the electronics are different. The ECM8000 electronics have changed a couple of times over the years so if may be that they're the same now. 



> I was looking at some measured 5-48K curves for the Behringer and it looks like the tails are more like 24dB/oct. The tails don't really matter for someone measuring a room but they could make a difference for someone designing a crossover because of errors in the calculated phase using a Hilbert transform. As an experiment, I built a fake cal file extending down to 1Hz and ran a Hilbert transform to get the phase. Then I truncated the file to 20Hz and ran the HBT again. The phase error at 20Hz was about 70 degrees with the truncated file.


You have to be careful with using Hilbert Transforms on condenser mic freq response data since condenser mics aren't minimum phase.


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## Dennis H

*Re: Cross-Spectrum Microphone Calibration Service*



Anechoic said:


> You have to be careful with using Hilbert Transforms on condenser mic freq response data since condenser mics aren't minimum phase.


 Hmmm, interesting. I'm no expert but I can't imagine a mechanism where a mechanical transducer and analog electronics wouldn't be minimum phase. There have been a lot of discussions about that with speaker drivers, cone breakup modes, baffle diffraction, etc. and it always turns out (as far as I know) that it is behaving as a minimum phase system even though it doesn't appear that way at first. BUT.... the HBT is making assumptions and it's subject to computation errors if you don't do things like extending the tails beyond the measured values. You have to do that with speaker drivers and I'd imagine you have to do it with mics as well.


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## Anechoic

*Re: Cross-Spectrum Microphone Calibration Service*

I've heard it repeated by extremely trustworthy sources (including people who have written some of the books on my shelf and have written ANSI/IEC microphone standards) that it is indeed the case, but have never seen a detailed explanation as to how/why.

The condenser mic is a fundamentlally different transducer than a loudspeaker driver- the loudspeaker is a linear motor that can be modeled by 2-D array of point sources on a plane while a condenser mic is a capacitor of varying charge and their mathematical models exhibit very different behavior (for example the response of the condenser mic is independent of frequency below the diaphragm resonance). It is my understanding that dynamic mics and ribbon mics, which basically act as loudspeakers in reverse, are minimum phase but condensers are not.


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## Anechoic

*Re: Cross-Spectrum Microphone Calibration Service*

*For anyone interested in purchasing a calibrated ECM8000 or who wants their own mic calibrated:*


Most of my suppliers are out of stock of ECM8000 and won't have a reliable supply until mid-March. I am able to get them one at a time and I am filling back orders but please be aware it may take a couple of weeks to fill new orders. As always, I do take pre-orders and I ship them on a first-come-first-served basis. 
I normally turn around mic calibrations in 48 hours. Please be aware that I will be traveling on business from March 16 to March 23 so any units I receive for calibration after March 11 won't be returned until the week of the 23rd.


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## Dennis H

*Re: Cross-Spectrum Microphone Calibration Service*



Anechoic said:


> I've heard it repeated by extremely trustworthy sources (including people who have written some of the books on my shelf and have written ANSI/IEC microphone standards) that it is indeed the case, but have never seen a detailed explanation as to how/why.
> 
> The condenser mic is a fundamentlally different transducer than a loudspeaker driver- the loudspeaker is a linear motor that can be modeled by 2-D array of point sources on a plane while a condenser mic is a capacitor of varying charge and their mathematical models exhibit very different behavior (for example the response of the condenser mic is independent of frequency below the diaphragm resonance). It is my understanding that dynamic mics and ribbon mics, which basically act as loudspeakers in reverse, are minimum phase but condensers are not.


 Thanks, Herb. I guess I'll have to take your word for that. Just curious, how could you ever use a condenser mic to design a crossover if it's introducing excess-phase errors? Seems like all the measurement and crossover programs assume the cal file is minimum phase and experience shows they work pretty well.


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## Anechoic

*Re: Cross-Spectrum Microphone Calibration Service*



Dennis H said:


> Thanks, Herb. I guess I'll have to take your word for that. Just curious, how could you ever use a condenser mic to design a crossover if it's introducing excess-phase errors?


About all you can do is trust in your cross-over design theory. That said most pro measurement mics are designed to have a relatively flat phase response up to 15-20 kHz, but that doesn't help you with an ECM8000 unfortunately.

Over the past week I made another attempt to get phase data for my measurement mics with no success. In the case of BSWA, in what I ca only guess is a language-barrier problem, no matter how many times I ask for "phase response" and "phase data" for the MP201, they keep sending me frequency response curves. 



> Seems like all the measurement and crossover programs assume the cal file is minimum phase and experience shows they work pretty well.


I'll have to try and dig it up, but when I first started doing microphone measurements, I used to give phase results generated by the Hilbert transform. When I learned that condenser mics weren't minimum phase devices, I found a generic freq and phase response curve for a measurement mic. I scanned in the frequency response, ran the Hilbert alogorthim on the data and compared the resulting phase response to the measured curve - and they weren't the same. that little exercise scared me straight.


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## Ricci

*Re: Cross-Spectrum Microphone Calibration Service*

Herb,

Do you know what the useable spl limit for the ECM8000 is? Seems to be about 120db or less?


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## lovebohn

*Re: Cross-Spectrum Microphone Calibration Service*



Ricci said:


> Herb,
> 
> Do you know what the useable spl limit for the ECM8000 is? Seems to be about 120db or less?


Good question!


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## Anechoic

*Re: Cross-Spectrum Microphone Calibration Service*



Ricci said:


> Herb,
> 
> Do you know what the useable spl limit for the ECM8000 is? Seems to be about 120db or less?


I've tested it up to 114 dB with no problems. When I get back from my trip I'll run some tests and see if I can find a definitive limit.


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## Ricci

*Re: Cross-Spectrum Microphone Calibration Service*



Anechoic said:


> I've tested it up to 114 dB with no problems. When I get back from my trip I'll run some tests and see if I can find a definitive limit.


That'd be great. I seemed to have run into some output/ distortion limits with the mic while doing some close mic (2 or 3") low frequency tests. The apparent level that close up to the driver cone was somewhere between 120-125db.


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## Anechoic

*Re: Cross-Spectrum Microphone Calibration Service*



Ricci said:


> That'd be great. I seemed to have run into some output/ distortion limits with the mic while doing some close mic (2 or 3") low frequency tests. The apparent level that close up to the driver cone was somewhere between 120-125db.


I just ran a quick test comparing the distortion of my one of my reference mics (ACO Pacific 7052, rated to 144 dB) to an ECM8000 at 1 kHz.

At 115 dB, my ref mic gets 0.13% distortion, the ECM8000 reads 0.54% 

At 120 dB, my ref mic gets 0.22% distortion, the ECM8000 reads 0.81% 

At 125 dB, my ref mic gets 0.46% distortion, the ECM8000 reads 1.37%


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## Ricci

*Re: Cross-Spectrum Microphone Calibration Service*

Thanks Herb. 

Overall that doesn't seem too bad, but it looks like you want to keep things under 120db if you can for the ECM8000. Do you think that there would be a difference if the frequency was lower at like 32hz or 40hz?


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## Anechoic

*Re: Cross-Spectrum Microphone Calibration Service*

I'm falling behind trying to cal all those mics I sold last week, but when I get a chance, I'll run the test again at a lower frequency.


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## Ricci

*Re: Cross-Spectrum Microphone Calibration Service*

Thanks again for being so forthcoming with data and help with odd requests and questions. I think this distortion info will be very interesting for a lot of people. 

I'm going to go ahead and guess that there will be noticeably higher distortion on the LF test. Won't the lower frequencies cause greater deflection of the mics diaghram for a set SPL?


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## Anechoic

*Re: Cross-Spectrum Microphone Calibration Service*



Ricci said:


> I'm going to go ahead and guess that there will be noticeably higher distortion on the LF test.?


Tests at 30 Hz:

At 115 dB, my ref mic gets 1.8% distortion, the ECM8000 reads 3.1% 

At 120 dB, my ref mic gets 2.95% distortion, the ECM8000 reads 5.0% 

At 125 dB, my ref mic gets 4.2% distortion, the ECM8000 reads 7.4%

FWIW, this is a different ECM8000 than the one used for the 1 kHz test.


----------



## Ricci

*Re: Cross-Spectrum Microphone Calibration Service*

Well...That's eye opening. That could explain some of the things I was seeing. I can only assume that the distortion will get even higher the lower the frequencies get. Looks like you should keep things under 110db when using this mic to remain clean. Not that any one serious about high SPL measurements would be using an ECM8000 in the first place.

Do you think that the ECM will compress the signal somewhat above 120db?


----------



## Anechoic

*Re: Cross-Spectrum Microphone Calibration Service*



Ricci said:


> Well...That's eye opening. That could explain some of the things I was seeing. I can only assume that the distortion will get even higher the lower the frequencies get. Looks like you should keep things under 110db when using this mic to remain clean.


That sounds like good advice.



> Do you think that the ECM will compress the signal somewhat above 120db?


I think that it depends on the mechanism that is causing the distortion, but my guess would be that you would see clipping rather than compression. I'll have to but the mic on an o-scope and check some waveforms at high amplitudes to see what's going on.


----------



## Anechoic

*Re: Cross-Spectrum Microphone Calibration Service*



Anechoic said:


> Over the past week I made another attempt to get phase data for my measurement mics with no success. In the case of BSWA, in what I can only guess is a language-barrier problem, no matter how many times I ask for "phase response" and "phase data" for the MP201, they keep sending me frequency response curves.


BSWA finally got back to me with a phase curve (theoretical I suspect) for the MP201 microphone. I'm going to have to spend some time experimenting to see if it's useful, but if it is, I may be adding microphone phase measurements to my repertoire.


----------



## Anechoic

*Re: Cross-Spectrum Microphone Calibration Service*

One other thing - when ordering the calibrated ECM8000s, I've gotten a lot of requests from people (most in this forum) for calibrations down to 10 Hz and up to 25 kHz. My normal default was to do 20Hz to 20kHz, but with so many people asking for the extended frequency response, and me having problems trying to keep track of those requests,* I am now generating 10 Hz to 25 kHz FR by default for calibrated ECM8000s.*. If you want 10Hz to 25kHz you no longer have to ask, it will come that way.

For microphones sent to me for calibration, those will continue to be 20 to 20 so you'll have to ask for the extended response.

I will also continue to perform 5 Hz calibrations and freq responses at up to additional 2 angles at no charge for the $85 and $100 mics, but again you'll have to ask for those. Also note that asking for those additional measurements may delay your order.


----------



## Anechoic

*Re: Cross-Spectrum Microphone Calibration Service*

so I've been asked here and other places whether ECM8000 have a lot of unit-to-unit variation and I usually answer by pointing to a plot done by someone else that shows a bunch of units compared with each other.

I finally got around to putting together a plot of mics I've sold - this is about 40 mics and represents about 1/3 of the ECM8000's I've measured over the last year (with the bulk of them mics from the newest Behringer run with the serial numbers). Thought people might be interested in seeing it:










Another interesting observation: based on the last bunch of mics I received it seems that the high-frequency variation is based on the location of the mic capsule in the end of the wand - the greater the capsule is recessed compared with another unit, the larger the difference.


----------



## Ricci

*Re: Cross-Spectrum Microphone Calibration Service*

Good stuff. Looks like the unit to unit variation has a range of around 6db or more on both ends of the spectrum.:gulp:. Calibrating your ECM or buying one with the calibration done already seems like a necessary evil.


----------



## lcaillo

*Re: Cross-Spectrum Microphone Calibration Service*

This data needs to be made into a sticky to emphasize the importance of having some actual reference data rather than making assumptions regarding the response of a mic.


----------



## Anechoic

*Re: Cross-Spectrum Microphone Calibration Service*



lcaillo said:


> This data needs to be made into a sticky to emphasize the importance of having some actual reference data rather than making assumptions regarding the response of a mic.


So long as you keep the title intact, feel free to use/distribute the plot for whatever.


----------



## brucek

*Re: Cross-Spectrum Microphone Calibration Service*



> This data needs to be made into a sticky


It's been there for two days.... 

brucek


----------



## Anechoic

*Re: Cross-Spectrum Microphone Calibration Service*

I've gotten a couple of inquiries about sound level meter measurements, so let me formalize the policy: 

I will perform on-axis and random incidence (free field) measurements of any SLM for $60 (which includes return shipping). That will include measurements at A/C/flat weighting as desired (one, or all of the above). This will use the same free-field testing method as my mic meaurements and will be non-NIST traceable. You can see a sample report of a sound meter calibration here (C-weighting only in this example). The typical report will be given for 10Hz to 25kHz but I'll go down to 5Hz upon request.

If you have a sound level meter with a 1/2-inch microphone (like the Galaxy CM-140, Tenma/Extech/etc lines or any number of meters, but *not* the Radio Shack meters) I can also perform a NIST traceable calibration and adjustment of the meter at 125 Hz, 250 Hz, 500 Hz and 1000 Hz and 74/84/94/104/114 dB. If the pressure field-to-free field adjustment data is available, I can also give you data at 2000 Hz and 4000 Hz. The price for this service is $30, including return shipping. You get a much simplified report showing the 20 (or 30) data points plotted against the ANSI limits and a table with the relative levels. 

The price for the combined free-field measurements and the calibration-level adjustment is $75 - that is, that's the price for mere mortals. *If you mention Home Theater Shack when you contact me, I'll do everything for $65 (return shipping included).* As with the mic cal, I should be able to turn around the unit in 48-hours after receiving it.

For those that don't want to part with their meter, you can buy an acoustic calibrator (that typically calibrate at one or two levels and one or two frequencies) for a couple of hundred bucks.

One thing to be aware of - the absolute calibration level of your meter will drift with changing temperature, humidity and altitude, so don't expect that any adjustment I can do will be spot on for ever. If you are really looking for your meter to be calibrated to a high degree of accuracy on a regular basis, it might be worthwhile to invest in an acoustic calibrator.


----------



## Tchao

*Re: Cross-Spectrum Microphone Calibration Service*

Hello,
First, I have to say that my english is not fluent and I will try to do my best to improve it : I apologize for that :hide:
second, it's my first post, and I expect to be in the "tolerance 0" of this forum, because I did'nt understand the entire rules that I agreed ...
Third: thank you Herb for your explanations, even though I don't understand every thing.

My questions to Herb:
I have a microphone from my pioneer audio/video multi-channel receiver with mcacc auto-calibration system.
Q1:Is-it possible to send you this microphone (the only one I have) to have a file of its calibration (10-25KHz) to use it with REW software ?
Q2: when you wrote "65$ for the combined free-field measurements and the calibration-level adjustment ", is it the same price when the microphone comes from France ? (that's why my english is not good :duh
Q3: is there somewhere an explanation about a "NIST traceable calibration" ? because in the example of calibration it's written that's it's not a NIST traceable calibration. So what a Nist Traceable calibration has special ? is it a certificate which proves that the calibration is under NIST standard and is as "true" as possible ?

Sorry for this questions so simple compared the others you debate here.


----------



## Anechoic

*Re: Cross-Spectrum Microphone Calibration Service*

Sorry Tchao, I didn't see this post.



Tchao said:


> Hello,
> 
> My questions to Herb:
> I have a microphone from my pioneer audio/video multi-channel receiver with mcacc auto-calibration system.
> Q1:Is-it possible to send you this microphone (the only one I have) to have a file of its calibration (10-25KHz) to use it with REW software ?


I don't know - if the microphone has conventional power and signal connections, then yes, but if it uses some propriety Pioneer connection, then no.



> Q2: when you wrote "65$ for the combined free-field measurements and the calibration-level adjustment ", is it the same price when the microphone comes from France ? (that's why my english is not good :duh


I would have to charge extra for the international shipping. And don't worry about your English, it's much better than my French 



> Q3: is there somewhere an explanation about a "NIST traceable calibration" ? because in the example of calibration it's written that's it's not a NIST traceable calibration. So what a Nist Traceable calibration has special ? is it a certificate which proves that the calibration is under NIST standard and is as "true" as possible ?


In short, NIST-traceable basically means that the process and techniques used in the calibration can be traced back to techniques outlined in standards recognized by the U.S. National Institute of Standards and Technology (usually ANSI, IEC, ISO, ASTM, etc standards) and the instrumentation used in the process have been calibrated by NIST or a NIST-accredited laboratory. Essentially is means that the NIST-traceable calibration would hold up in a court of law.

Now the processes I use for the calibration are consistent with IEC 60268 methods and the equipment I use have been calibrated by NIST-traceable labs. If I wanted to go through the process of performing a statistical analysis of my methods using NVLAP methods I could probably assert NIST-traceability, but I don't want to deal with the potential liability issues so I just slap "not NIST traceable" on the reports to reduce the chance of lawsuits.

The point calibrations at 125, 250, 500 and 1000 Hz use an acoustic calibrator that meets ANSI S1.40 and has been calibrated by an accredited 3rd party lab so I have to problem asserting NIST traceability for those measurements.


----------



## Anechoic

*Re: Cross-Spectrum Microphone Calibration Service*

Just as an FYI, it took me a while but I finally have inventory again for the "full" calibrated units so I'm back to same-day shipping for orders placed before 1pm eastern time. I have a limited number of the "basic" calibration so I imagine those will get backordered pretty quickly.

Please note that "special orders" (extended freq response, multiple angles, etc) will still take 4-5 business days to ship.

Also, summer tends to be a busy time for my noise control-consulting business. If you want to send me a mic to cal but you need it back quickly, please contact me, before you mail it so I can see if I can fit it into my schedule. If you just send it, it may be a week or so before I can get it back to you.


----------



## cavchameleon

*Re: Cross-Spectrum Microphone Calibration Service*

This is very useful info Anechoic! Thanks for all the info and link to the acoustic calibrator.

I'm looking for a link to your site (for purchase of a calibrated mic) but cannot seem to find it in your alias pop-up.


----------



## Anechoic

*Re: Cross-Spectrum Microphone Calibration Service*



cavchameleon said:


> I'm looking for a link to your site (for purchase of a calibrated mic) but cannot seem to find it in your alias pop-up.


Here you go.


----------



## cavchameleon

*Re: Cross-Spectrum Microphone Calibration Service*



Anechoic said:


> Here you go.


Thanks, I appreciate it! Is there a way to put in in a link to your alias for future inquires (would make it very easy).


----------



## Anechoic

*Re: Cross-Spectrum Microphone Calibration Service*

I added it to my profile so when you click on "Visit Anechoic's homepage!" under "Anechoic" it goes to that page. Is that what you meant?


----------



## cavchameleon

*Re: Cross-Spectrum Microphone Calibration Service*



Anechoic said:


> I added it to my profile so when you click on "Visit Anechoic's homepage!" under "Anechoic" it goes to that page. Is that what you meant?


Yep! :bigsmile: Thanks a lot, this was what I was looking for in the first place and could not find a link.

Thanks!
Ray


----------



## Tchao

*Re: Cross-Spectrum Microphone Calibration Service*



Anechoic said:


> Sorry Tchao, I didn't see this post.
> 
> No problem !
> 
> I don't know - if the microphone has conventional power and signal connections, then yes, but if it uses some propriety Pioneer connection, then no.
> it's a microphone with a jack connexion and no power, only the jack connexion. I tried it with REW, it works well, but without a calibration file it's not really usefull ...


thank you for the answers, I will contact you by email as "Tchao", just to have the link of this conversation.

Bye :wave:


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## cavchameleon

Anechoic,

Hi! Just placed an order for a full spectrum ECM8000. Just a question, I also have a dbx RTA-M mic. Is it worth getting this one calibrated (would it be more accurate than the ECM8000)? Just wondering if the capsule in the dbx is better than the Behringer version.

Thanks,
Ray


----------



## Anechoic

cavchameleon said:


> Anechoic,
> 
> Hi! Just placed an order for a full spectrum ECM8000. Just a question, I also have a dbx RTA-M mic. Is it worth getting this one calibrated (would it be more accurate than the ECM8000)? Just wondering if the capsule in the dbx is better than the Behringer version.
> 
> Thanks,
> Ray


Just got your order and I'll be shipping it shortly.

As for the RTA-M, I've measured a few of them (in fact I own one that came with my Sencore RTA) and they're more consistent from unit-to-unit but they still have the upper frequency diffraction bump that most mics have, although it's higher in frequency than the ECM800's because of the smaller diameter of the ECM8k. 

I haven't taken one apart, but I would be surprised if the RTA-M and the ECM8000 used different mic capsules (or at least unrelated capsules). I suspect that dbx's OEM is more careful in assembling the units which accounts for their better consistency. But that's speculation on my part.


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## cavchameleon

Anechoic said:


> Just got your order and I'll be shipping it shortly.
> 
> As for the RTA-M, I've measured a few of them (in fact I own one that came with my Sencore RTA) and they're more consistent from unit-to-unit but they still have the upper frequency diffraction bump that most mics have, although it's higher in frequency than the ECM800's because of the smaller diameter of the ECM8k.
> 
> I haven't taken one apart, but I would be surprised if the RTA-M and the ECM8000 used different mic capsules (or at least unrelated capsules). I suspect that dbx's OEM is more careful in assembling the units which accounts for their better consistency. But that's speculation on my part.


Thanks Anechoic!!! I'll let you know when I receive the mic. As far as the RTA-M, is the price of calibration the same as the ECM8000? I think it would still be nice to have it calibrated if I plan to use it at all. If you need to PM me the info (not sure if price/etc allowed in thread forums), that would be fine.

Ray


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## cavchameleon

Anechoic,

Received my calibrated ECM8000 today. Thanks a lot for such quick service!!!

Ray


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## Sonic Icons

Hi,

First, I would like to thank you (Anechoic) for helping this forum with your calibration services and technical insights. I have a question about the "generic" Behringer ECM-8000 calibration file on the Downloads page, with filename "ECM8000-CS.cal". Is this file based on an average of measurements of ECM-8000's done in your lab? To me, the "generic" calibration file looks flatter in the bass than I would have guessed from the range of response curves you showed in message #43. The "generic" file has -1.40 dB at 20 Hz, -0.54 dB at 25 Hz, while the curves in message #43 appear to range from -5.5 dB to +1 dB at 20 Hz, and from -4 dB to +1 dB at 25 Hz.


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## brucek

> I have a question about the "generic" Behringer ECM-8000 calibration file on the Downloads page, with filename "ECM8000-CS.cal". Is this file based on an average of measurements of ECM-8000's done in your lab?


No, Cross Spectrum does not load the files on our download page.

The ECM8000 generic calibration file is from Sonnie's personal ECM microphone that Cross Spectrum calibrated for him.

Of the calibrations that were carried out on this microphone, we chose the Frontal incident (horizontal on-axis 0 degrees), 1/6th octave spacing file and reduced it to two decimal places. It should be fine for home use.

If you require more accuracy, it's best to get your own microphone calibrated.

brucek


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## Sonic Icons

Thank you for the clarification - the "generic" ECM-8000 calibration file on the downloads page is clearly within range of the response curves shown in #43, if it is understood to be the curve for one particular microphone, rather than an average of all the ECM-8000s tested by Cross-Spectrum.

I agree that the data (the variation of the curves in #43) shows that individual calibration is needed for accurate measurements. Also, it is noteworthy that there is a lot of variation in the deep bass (20 - 100 Hz) (the critical frequency range for measuring subwoofer room response), as well as the highs (5 - 20 kHz).


----------



## cavchameleon

Sonic Icons said:


> Thank you for the clarification - the "generic" ECM-8000 calibration file on the downloads page is clearly within range of the response curves shown in #43, if it is understood to be the curve for one particular microphone, rather than an average of all the ECM-8000s tested by Cross-Spectrum.
> 
> I agree that the data (the variation of the curves in #43) shows that individual calibration is needed for accurate measurements. Also, it is noteworthy that *there is a lot of variation in the deep bass (20 - 100 Hz) (the critical frequency range for measuring subwoofer room response), as well as the highs (5 - 20 kHz)*.


Yep, as brueck mentioned, it's pretty much fine for the home user, but if you want accuracy, go ahead and get a calibrated one from Cross Spectrum (you'll get it within a couple days of ordering). He has the best price for a calibrated ECM-8000 (there are many mics out there that you can purchase that are calibrated, most being several times the cost of the Behringer, and for most, not necessary.

Ray


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## Sonnie

To confirm... we have no issues with Herb quoting prices here at the Shack if he so desires. :T


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## cavchameleon

Sonnie, 
I didn't know if I would be able to quote the price. Since I just purchased it from Herb, here is some info.

Sonic Icons,
Here is Herb's site:
http://www.cross-spectrum.com/measurement/calibrated_behringer.html
You have a choice of to levels of calibration:
1 - Freq response only ($85)
2 - Freq response and Polar Data ($100)

His site has a lot of useful info if you have not checked it out already.

Ray


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## JohnM

As an aside to all this, with REW V5 the cal data can (ideally should) include phase as well as SPL correction, so should look at including phase data from calibration.


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## lcaillo

If we were going to do so, would it not make sense to calibrate the mic/preamp as a system, since there may be more phase effect in the combination than just in the mic?


----------



## VintageGold

I see you also calibrate the Galaxy CM-140, but along with selling pre-calibrated ECM8000, do you also sell pre-calibrated CM-140's? I'm planning on picking up a CM-140 but wanted to find out if these are available before I purchase from some where like Musician's Friend.


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## Anechoic

A couple of things:

1. If you ask me a question here and I don't respond within 24-hours, shoot me an email directly and I'll respond here. For some reason I don't always get the thread update emails.

2. Here's a head's up - I offered to do freq-response curves at additional angles for my calibrated mics for free. However, it's become a bit of a hassle to keep track of the various special orders. As a result, I'm going to change things a bit - as of August, I'm going to offer 4 mic models: a) "Basic" with 0-deg freq response for $85, b) "Basic-Plus" with 0/45/90 deg for $90, c) "Extra" with 0-deg freq response, polar, noise floor, and sensitivity for $100 and d) "Extra-Plus" with the "Extra" package + 0/45/90 deg for $110. On the plus side, I'm going to do freq-response down to 5 Hz by default.

This is going to be a price increase but on the plus side, I'll try to stock up on these models so there won't be a wait for people who want the 45/90-deg measurements. 

*However, I will still do the extra measurements for free for orders placed before Aug 1, so if you want to save some money, place your order before then.*

Now on to questions:



> If we were going to do so, would it not make sense to calibrate the mic/preamp as a system, since there may be more phase effect in the combination than just in the mic?


For my measurements, it doesn't matter since I don't measure phase . 



> I see you also calibrate the Galaxy CM-140, but along with selling pre-calibrated ECM8000, do you also sell pre-calibrated CM-140's?


I don't sell pre-calibrated meters and I don't imagine I ever will because there are potential liability issues on my end if people purchase it from me for the purpose of using it in a legal setting. However, if you buy a meter, you can have it shipped directly to me, and I'll calibrate it and send it on to you which should at least save a couple of bucks in shipping costs as well as a couple of days of time.


----------



## Dennis H

Anechoic said:


> as of August, I'm going to offer 4 mic models: a) "Basic" with 0-deg freq response for $85, b) "Basic-Plus" with 0/45/90 deg for $90, c) "Extra" with 0-deg freq response, polar, noise floor, and sensitivity for $100 and d) "Extra-Plus" with the "Extra" package + 0/45/90 deg for $110. On the plus side, I'm going to do freq-response down to 5 Hz by default.


 Do the Basic and Basic-Plus not include 1K sensitivity? Seems like everyone would need that.


----------



## Anechoic

Dennis H said:


> Do the Basic and Basic-Plus not include 1K sensitivity? Seems like everyone would need that.


Correct, the Basic and Basic-plus do not include 1 kHz sensitivity. I thought more people would want sensitivity but it turns out that very few people care about - in fact more people want the polar response than the sensitivity.


----------



## Dennis H

Anechoic said:


> Correct, the Basic and Basic-plus do not include 1 kHz sensitivity. I thought more people would want sensitivity but it turns out that very few people care about - in fact more people want the polar response than the sensitivity.


 That's amazing. How are they measuring SPL? An RS meter that may or may not be within 3dB?

On another subject, can you calibrate above 24K for an extra charge? Many people are using 96K sound cards with a nominal 48K capability so it would be nice to have a general idea what the mic is doing up there, even if the calibration isn't perfect.


----------



## Anechoic

Are people using the ECM8000 to measure SPL? I assumed most people were just using them for freq response curves.

The problem with >24kHz measurements is that I don't have calibration curves for my reference mics that go that high. The next time I send in my ref mic for calibration I'll ask them to push the curve out to 40+kHz and then maybe I'll offer the service for an extra charge.


----------



## Dennis H

ARTA (along with some other programs, don't know about REW) has a setup routine where you calibrate your mic preamp and sound card with tones and a voltmeter so you can do your measurements in dB SPL if you can plug in the mic's sensitivity.


----------



## Sonnie

Dennis H said:


> That's amazing. How are they measuring SPL? An RS meter that may or may not be within 3dB?





Anechoic said:


> Are people using the ECM8000 to measure SPL?


Some will use the RS meter, some the Galaxy CM-140 and others the ECM8000. SPL is not that terribly important. For level matching, most receivers and processors have Audyssey or equivalent for setting up the system anyway. :nerd:

If you wanna just see how loud it will get, for whatever that may be worth, getting within 3db should be plenty sufficient, unless someone really has an OCB about being the SPL king, like the kids in the car stereo crank off contests. :dumbcrazy:


----------



## Anechoic

I know that you _can_ do SPL measurements with the ECM8000 (I am an ARTA user & FWIW a Type 1 mic + ARTA gets you the same results as a Type 1 meter) I was just curious if anyone is actually doing it. 



Sonnie said:


> Some will use the RS meter, some the Galaxy CM-140 and others the ECM8000. SPL is not that terribly important. For level matching, most receivers and processors have Audyssey or equivalent for setting up the system anyway. :nerd:


which sounds about right.

The reason I do sensitivity measurements is so people can do measurements but no one (outside of pros) really seemed to care. Interesting...


----------



## cavchameleon

Interesting...
I use a calibrated meter for SPL (well, use to, but just let Audyssey do that adjustment now - sometimes comfirm with the meter, but really not necessary). For SPL, it is MUCH easier to just use a calibrated meter then a calibrated mic with computer/software (no setup time) IMO. As Sonnie mentioned, there are 'some' that want to know max spl (I prefer to keep my hearing). I have use my meter just out of curiosity to see where my dynamic peaks are hitting with normal dialog at 85db (meter showed 109db on peaks), but only because I wanted confirmation that peak levels do not sustain long enough for hearing damage.

Ray


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## Dennis H

The crowd where I usually hang out is into designing speakers so having the levels calibrated is useful when you're mixing and matching drivers that may have been measured at different times and under different conditions. The most common way is to normalize everything to 2.83V/1m when you save the files.


----------



## cavchameleon

Well, then that makes sense, especially if you want absolute correct level matches, also when designing/confirming crossovers. But, as Anechoic mentioned, most users simply want correct FR and Polar response (the two things I looked for). I haven't built speakers in a LONG time. It would be fun to do it again, especially with all the software available.

Ray


----------



## VintageGold

When an SPL meter like the Galaxy CM-140 or RS unit is calibrated, does the calibration process simply provide a cal file like what's used for the ECM8000 or is it actually being calibrated so it, as a standalone instrument, measures dB's more accurately, like what you would use one of these for:

http://www.galaxyaudio.com/CMC200.jsp

Maybe I've overlooked something here, but from what I've read the ECM8000 has a wider frequency range (15 Hz to 20 kHz) than the Galaxy CM-140 (31.5Hz to 8KHz), so why would you want to use the Galaxy to do room measurements beyond typical SPL readings?

What I'm getting at is this: Is it worth it to own one of each and have them both calibrated: the ECM8000 with its cal files to correct for frequency response and polar data, and the Galaxy CM-140 to check for SPL? I'd still like to do SPL measurements (level matching systems like my car stereo and headphones, checking noise levels, etc.) w/out having to hook up a whole rig to do this.


----------



## cavchameleon

Hi Dan,

I have a comparable SPL meter to the one above, but from TENMA. It has the same specs and I only use it for level matching with pink noise. As for doing SPL measurements outside the freq range of this meter, for a stand alone product you can look at Goldline products, but they are expensive.

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=390-815
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=390-805

So, if you have a laptop with REW, that may be the better choice IMO. The 2nd one above from Goldline is an incredible piece, but you can buy a laptop, calibrated ECM8000, and outboard sound card with phantom voltage for less then the Goldline unit.

Ray


----------



## brucek

> When an SPL meter like the Galaxy CM-140 or RS unit is calibrated, does the calibration process simply provide a cal file like what's used for the ECM8000 or is it actually being calibrated so it, as a standalone instrument, measures dB's more accurately


The calibration comes in the form of a calibration file in easily read text form.



> Maybe I've overlooked something here, but from what I've read the ECM8000 has a wider frequency range (15 Hz to 20 kHz) than the Galaxy CM-140 (31.5Hz to 8KHz), so why would you want to use the Galaxy to do room measurements beyond typical SPL readings?


The calibration file extends the accuracy range to 20KHz for the Galaxy, just as it does for the ECM8000. So, if your Galaxy was down by 10dB at 20KHz, then the file would show +10dB for the 20KHz entry. This would render the reading flat once the calibration was added in REW (or manually).

brucek


----------



## JohnM

brucek said:


> The calibration file extends the accuracy range to 20KHz for the Galaxy, just as it does for the ECM8000. So, if your Galaxy was down by 10dB at 20KHz, then the file would show +10dB for the 20KHz entry. This would render the reading flat once the calibration was added in REW (or manually).


Oops, typo there, it would show *-*10dB, the cal file contains the actual response of the mic/meter.


----------



## VintageGold

First of all, thanks for all the replies here from other members, your input has been very helpful.


Ray,

I checked out that TENMA meter.

http://www.mcmelectronics.com/product/TENMA-72-945-/72-945

All the specs are very similar to the Galaxy meter and actually comes with some nice extras like a hard carrying case, AC adapter, and a USB cable. It seems like the USB connection might actually make connecting it to a computer a little easier. Have you ever used it as a test mic in the REW application?

For all,

Going back to my question about the calibration... I now understand that a cal file is included to show the frequency deviations to adjust inside REW, but I was also hoping to know if the SPL meter calibration can be done for the SPL measurement itself, much like what the Galaxy CM-C200 is used for, to calibrate it at 94 dB and 114 dB.

http://www.galaxyaudio.com/CMC200.jsp

The SPL level calibration device would be nice to have, but it's about $180-$250 on it's own, depending on where you look. I think it would be really handy to have something that could function as a calibrated, standalone SPL meter as well as being able to use it with REW or other programs.


----------



## cavchameleon

Dan,

Tenma also makes an expensive calibrated model:

http://www.mcmelectronics.com/product/TENMA-72-6635C-/72-6635C

This is more comparable to the Galaxy version, but the model you are looking at is just fine (there is another version of the one you are looking at for a bit more money that can do data logging:

http://www.mcmelectronics.com/product/TENMA-72-947-/72-947

None of them IMO is a flat as using an ECM8000 (calibrated), which is what I use for REW, but it really should be fine if you can get a cal file for it and take that into account as mentioned above.

Ray


----------



## Anechoic

VintageGold said:


> When an SPL meter like the Galaxy CM-140 or RS unit is calibrated, does the calibration process simply provide a cal file like what's used for the ECM8000 or is it actually being calibrated so it, as a standalone instrument, measures dB's more accurately, like what you would use one of these for:
> 
> http://www.galaxyaudio.com/CMC200.jsp


brucek addressed the rest of your post, but I just wanted to mention that I can do either/both types of calibration (frequency response correction curves and level/sensitivity adjustments) for SLMs with 1/2-inch type microphones.


----------



## Anechoic

Hi All,

Just a friendly reminder that prices will change starting on Saturday, Aug 1. If you want measurements at extra angles without paying extra, speak now or forever hold your piece.

That said, I will let slip that it won't be a total loss for HS readers if you miss the deadline. Stay tuned...


----------



## JimP

Anechoic,

Where can we find your current prices for either buying a ECM8000 with calibration or having our own ECM8000 calibrated. I'd want it accurate to either 10 or 15 hz...


----------



## Anechoic

JimP said:


> Anechoic,
> 
> Where can we find your current prices for either buying a ECM8000 with calibration or having our own ECM8000 calibrated. I'd want it accurate to either 10 or 15 hz...


Click on my name to find prices for pre-calibrated ECM8000 sales. Having your own mic calibrated is $55 for basic calibration, +$10 for polar measurements, +$10 for noise floor/sensitivity. Extra angles are free, but as of Sat, extra angles will be $5 per additional angle. The new price structure for mic sales (again, starting Aug 1) is described here.


----------



## chris319

I had Herb (Cross Spectrum Labs) test an E-V RE510 for me a few months ago and was very satisfied with the service. The mic, not so much. Herb is the real deal.

Herb, are you able to test mics at frequencies other than the standard third-octave intervals? The reason I ask is because I use a program called Voxengo Curve EQ to approximate the inverse of a mic's measured frequency response and thus "flatten" it, and it has more and different frequencies available on its EQ than the third-octave values.

Thanks.


----------



## Anechoic

Thanks for the kind words.

I can do 1/6 octave.


----------



## hjones4841

For those on the fence about getting the calibrated ECM-8000, I recommend going for it. I received mine Friday (thanks for the fast service from Cross Spectrum) and there is quite a bit of difference between it and the generic curve from this website. (To be fair, that generic curve is from one mic and Cross Spectrum has posted the variation among samples of the ECM-8000).

I suppose it all depends on how accurate you want your calibration to be. But, that is why we do this, right?


----------



## Anechoic

BTW everyone, if you're in the Boston area, the Boston Audio Society will be holding a "microphone measurement clinic." A bunch of us who do various sorts of measurements (including Joe DeMarinis and possibly someone from Listen Inc.) will be there to talk about mic measurements and actually do some mic measurements. The plan right now is that Joe will be handling the mid-to-high frequency measurements and I'll be doing low-frequency measurements with my low-freq calibration rig. 

We're looking at Nov 21 or 22, and when we settle on a date, it will be posted on the BAS website.


----------



## Anechoic

FYI, in case anyone was wondering just how accurate my calibration process is, I did I little test to see how my measurement compare with mic calibrations performed by a NIST-traceable lab. I have several professional measurement microphones that are regularly calibrated by Scantek.

One of my more top-of-the-line microphones is a BSWA MP201. Scantek has calibrated this a couple of time using an electrostatic actuator (to get the pressure response) and then applying a free-field correction per ANSI/IEC standards. One such result is shown below (I do have a more recent cal, but I can't find the plot right now. FWIW, the mic FR didn't change):










So I took the data points off that plot, measured the MP201 using my freefield method (which is basically the substitution method using another calibrated mic) and plotted a comparison:










No tricks, no adjustments, no massaging the data, that's what I got using the same software, hardware and scripts I use to generate curves for all the mics I sell. There is a discrepancy at 20 kHz; the problem at those high frequencies is that the wavelengths are so small that every little thing can effect the result, including the microphone mounting method. Without knowing the exact free-field correction process Scantek uses I can't say who is more/less correct but I will note that both measurements are will within ANSI/IEC accuracy standards (which get larger at higher frequencies).


----------



## cavchameleon

Very nice Herb!!! It gives a lot of confidence in your technique and calibration skills (not that we did not have it before). Thanks again for such a great service!!!


----------



## nerdful1

Now this is a great excuse to take the Downeaster to Boston. 2 hours from OOB to Boston, listening to podcast, reading....
Most people I knew from my last meeting I went to at BAS are long gone either in the audio world or dead.

Think I will bring my mic with me too, maybe re-enlist in BAS.

Last BAS I went to, a bit fuzzy... either Acoustic Research, doing car audio tests with a PDP11, or some microphone clinic at BBN, I remember most of us were spending thousands on audio gear mass produced, and the speaker emphasized a microphone is mostly hand made, for only 700.00 or so. (circa 1978ish).


----------



## Anechoic

nerdful1 said:


> Now this is a great excuse to take the Downeaster to Boston. 2 hours from OOB to Boston, listening to podcast, reading....
> Most people I knew from my last meeting I went to at BAS are long gone either in the audio world or dead.
> 
> Think I will bring my mic with me too, maybe re-enlist in BAS.


We'd love to have you. The only problem is that it looks like we're going to have the meeting in Winchester, so getting from North Station to Winchester might be a bit of a haul. Although there is a commuter rail stop in Winchester, so I'm sure I or someone else could give you a ride to/from the station.


> Last BAS I went to, a bit fuzzy... either Acoustic Research, doing car audio tests with a PDP11, or some microphone clinic at BBN, I remember most of us were spending thousands on audio gear mass produced, and the speaker emphasized a microphone is mostly hand made, for only 700.00 or so. (circa 1978ish).


Wow, you are old!


----------



## Soundtek

brucek said:


> The calibration comes in the form of a calibration file in easily read text form.
> 
> 
> The calibration file extends the accuracy range to 20KHz for the Galaxy, just as it does for the ECM8000. So, if your Galaxy was down by 10dB at 20KHz, then the file would show +10dB for the 20KHz entry. This would render the reading flat once the calibration was added in REW (or manually).
> 
> brucek


Sorry I don't understand... why the mic need a calibration? It's not perfect yet?


----------



## JimP

Soundtek said:


> Sorry I don't understand... why the mic need a calibration? It's not perfect yet?


Look a few post up and see how much individual mics vary that are suppose to be the same. Yes, they're not perfect and require a correction file preferable for that individual mic. With the generic files, you always wonder just how far off you are actually reading.


----------



## Soundtek

Impressive.... For "home calibrations" is recommended anyway?


----------



## apinamies

Does the ECM8000 Premium+ come with a calibration file compatible with REW?


----------



## Anechoic

apinamies said:


> Does the ECM8000 Premium+ come with a calibration file compatible with REW?


Yes, all my mics (including the Premium+) came with cal files that can be used with REW and many other software packages.


----------



## apinamies

Do you still have those discounted Premium+ mics?


----------



## Anechoic

apinamies said:


> Do you still have those discounted Premium+ mics?


I'm running a special right now and I have a few left. They should ship during the week of Feb 28. If you need something sooner, you can get a mic a the normal price.


----------



## Anechoic

FYI, the last batch of mics I got included a microphone with a very unusual frequency response curve:










Because of this crazy response, I'm really not comfortable selling this mic at the regular price, so I'm selling it as a Premium+ model for $60 on my refurb page. You can download a copy of the full cal report  (which also shows the polar response) before you order to make sure you know what you're getting. The mic otherwise works fine (sensitivity and noise floor within norms), it just seems like it's an outlier.

It will ship within 24 hours.

edit: it's gone.


----------



## evilskillit

I have a PartsExpress EMM6 that came with a cal file. I was wondering if anybody has had one of these calibrated yet and how much it varied? I was wondering if I should use that file or the averaged EMM6 file offered here? I'll probably get mine calibrated some time when I've got a few bucks to throw at it, but I was wondering what you guys would do in the mean time.


----------



## Anechoic

Use the curve that came with your EMM-6, it will be closer than the average curve here. The individual EMM-6 curves aren't bad, and they seem to have improved some with the latest bunch.


----------



## evilskillit

Anechoic said:


> Use the curve that came with your EMM-6, it will be closer than the average curve here. The individual EMM-6 curves aren't bad, and they seem to have improved some with the latest bunch.


Ok thanks for the reply. Thats what I figured but it doesnt look much like any of the ones that constitue the default/average graph, thats what made me want to ask.


----------



## Anechoic

FYI, I have a few mini-tripods  leftover from another project, so I'm offering them with my calibrated mics for an additional $2 (to cover the shipping from the additional weight, I'm otherwise giving them away for free).

Offer good while supplies last.

edit: link should work now


----------



## JimP

Your link doesn't work.


----------



## Anechoic

JimP said:


> Your link doesn't work.


Well that's no good 

For now, just go here and scroll down to the April update just above the 'Buy' button.
_Posted via Mobile Device_


----------



## Anechoic

Hey guys,

FYI, my schedule is getting full for the rest of this month, so mic shipments may be delayed by up to a week. To compensate for that delay, I'm offering $10 off calibrated Behringer and Dayton microphone orders.

The discount will be applied to the cart when the order is placed.


----------



## bearberry

Hi,
I need to set up a measurement system for speaker design and room setup. Can I get by with just the Galaxy, or would a Dayton/Behringer mic also be required?

Thanks,
bearberry


----------



## Anechoic

bearberry said:


> Hi,
> I need to set up a measurement system for speaker design and room setup. Can I get by with just the Galaxy, or would a Dayton/Behringer mic also be required?
> 
> Thanks,
> bearberry


I provide calibration curves with the Galaxy Verified+ models, so you would be okay with just the meter. Order by midnight tonight and get an additional $5 off or a free pocket speaker with your HTS username (see the Thanksgiving thread, although keep in mind I'm out of stock in meters and won't start shipping them until later this week).


----------



## bearberry

Thanks for the quick response. will be ordering later, but first have to go see the Saskatchewan Roughriders win the Grey Cup!:T

www.cfl.ca


----------



## dondino

I just wanted to chime in here for anyone on the fence about ordering a calibrated mic through this service ... do it! ... The shipping was blazingly fast (YMMV) and there was great communication. Well worth the few extra bucks vs. an off the shelf mic. My experience, YMMV.


----------



## Anechoic

dondino said:


> I just wanted to chime in here for anyone on the fence about ordering a calibrated mic through this service ... do it! ... The shipping was blazingly fast (YMMV) and there was great communication. Well worth the few extra bucks vs. an off the shelf mic. My experience, YMMV.


Well, just so we don't set expectations too high, fast shipping happens when 1) I have product in stock, and 2) when I'm around to ship mics, both of which are conditions which seem to happen less often nowadays. In fact I'm actually traveling this week so mics won't ship until Saturday at the earliest (more likely early next week). As a result, I have temporarily reduced prices until pricing returns to normal. 

Speaking of which, I'll give HTSers another $5 off those mic sales prices (and don't forget the normal $5/$10 discount off the Galaxy meters). Just leave your HTS username on the "message to seller" on the last PayPal page. Prices go back to normal on Saturday.


----------



## pepar

What would make one choose the Dayton over the Behringer, or vice versa?


----------



## Anechoic

pepar said:


> What would make one choose the Dayton over the Behringer, or vice versa?


Behringer: higher quality accessories (case, mic clip), lower output impedance so it will be easier for low-quality pre-amps to drive.

Dayton: generally flatter response, lower noise floor, better unit-to-unit consistency.

IMO, as long as you have a decent quality pre-amp, the Dayton wins.


----------



## pepar

Anechoic said:


> Behringer: higher quality accessories (case, mic clip), lower output impedance so it will be easier for low-quality pre-amps to drive.
> 
> Dayton: generally flatter response, lower noise floor, better unit-to-unit consistency.
> 
> IMO, as long as you have a decent quality pre-amp, the Dayton wins.


Thanks. I have a browser tab open now on my PayPal account.

And thanks for extending the discount!

Jeff


----------



## Anechoic

Reason # 5009 why you should never trust an out-of-the box ECM8000 for critical measurements:










I'm selling this mic as a Premium+ for $65 since I can't bring myself to charge full price for this.

HTS members will get $5 off, leave your username in the "message to seller" box on the PayPal checkout page and I'll refund the $5.


----------



## Anechoic

Hey all,

I do have a small bit of bad news: my costs have have been going up over the last 10 months or so - the wholesale prices for both the Behringer and Dayton mics have increased and there was an increase in USPS shipping rates back in January. I ate the costs, but with some other costs increasing, I am going to have to raise my calibrated mic pricing. The plan is to raise prices by $5 across the board for all my mics (but not the meter).

Two bits of good news: one, I'm going to wait until late May/early June to raise the prices. I'm announcing the increase early because I know that as a consumer myself, I hate when prices unexpectedly rise overnight, so as a believer in the "do unto others" mantra I am extending a courtesy that I would like to see vendors extend to me.

The second bit of good news: I've been offering a $5 discount for HTS members on the Dayton mics and I've occasionally offered discounts on the Behringer mics. I will carry the discount forward for the Dayton mics and I will offer a permanent $5 discount for HTS members on the Behringer mics as well, so in effect HTS members won't see a price increase for those mics. 

Thanks guys, I appreciate the business and I appreciate HTS for giving me the opportunity to share.


----------



## michael123

Hello

I have ECM8000 stock unit and I would like to upgrade it to some much better, say beyond 1db precision within 15Hz-25Khz.. I got a warm recommendation for the calibrated Dayton EMM-6

1) I do not see the specification though, is it really 1db precision?
2) It is possible to buy the mic here: http://www.parts-express.com/pe/show...number=390-801 for 48$, and then download the calibration file free of charge. Where is the difference .. from the Basic calibration?
3) I do not understand the application of different measurements (Basic+, Premium, Premium+) to Room EQWizard. How REW is going to use the calibration files? E.g. is it going to influence phase measurements, waterfalls in REW? How? 
4) I have Tascam US-122, I hope it is still good for Dayton..

thanks,
Michael


----------



## pepar

michael123 said:


> Hello
> 
> I have ECM8000 stock unit and I would like to upgrade it to some much better, say beyond 1db precision within 15Hz-25Khz.. I got a warm recommendation for the calibrated Dayton EMM-6
> 
> 1) I do not see the specification though, is it really 1db precision?
> 2) It is possible to buy the mic here: http://www.parts-express.com/pe/show...number=390-801 for 48$, and then download the calibration file free of charge. Where is the difference .. from the Basic calibration?
> 3) I do not understand the application of different measurements (Basic+, Premium, Premium+) to Room EQWizard. How REW is going to use the calibration files? E.g. is it going to influence phase measurements, waterfalls in REW? How?
> 4) I have Tascam US-122, I hope it is still good for Dayton..
> 
> thanks,
> Michael


Not Herb, but the "precision" comes from the calibration that he does, i.e. the precision is in the calibration file that he generates in that it _precisely_ (within the stated tolerance) matches the response of the mic.

I have the Tascam, too, and just bought the Dayton Basic +. That level gives you calibration files for 0, 45 and 90 degrees. Zero and 90 are likely to be the only two that you use.

Jeff


----------



## michael123

Thanks,
I understand.

I see yet that the .CAL files are different from the .FRD as they do not have the phase information.
Does it mean that going beyond Basic has no effect?

Also, what is the difference between this and the personal calibration Daytone gives away now (for free)?


----------



## Anechoic

michael123 said:


> Hello
> 
> I have ECM8000 stock unit and I would like to upgrade it to some much better, say beyond 1db precision within 15Hz-25Khz.. I got a warm recommendation for the calibrated Dayton EMM-6
> 
> 1) I do not see the specification though, is it really 1db precision?


If you mean 1 dB precision out-of-the-box without the use of a calibration file, you _might_ get lucky and get an EMM-6 (or ECM8000) that flat, but it's been months since I've seen a Dayton (and years since I've seen a Behringer) with that kind of accuracy. There's a reason why pro mics from Earthworks, ACO Pacific, Bruel & Kjaer et all (which do have guaranteed +/- 1 dB or better accuracy) cost so much.

Now with a calibration file, yes, you can get accuracy in that ballpark.




> 2) It is possible to buy the mic here: http://www.parts-express.com/pe/show...number=390-801 for 48$, and then download the calibration file free of charge. Where is the difference .. from the Basic calibration?


There are two differences between the stock Dayton units and the calibration Daytons I sell:

1) The stock Dayton correction curve bandwidth is 20 Hz to 20 kHz, while my mics are calibrated from 5 Hz to 25 kHz.

2) I believe that my correction curves are more accurate than the stock curves (I have written up my procedures and some comparisons between my measurement results and the results generated by NIST-traceable labs in other threads). 

That said, the stock Dayton curves are certainly in the ballpark, so if all you need is 20 Hz to 20 kHz data for the lowest price, I would recommend just buying the stock Dayton straight from PE.



> 3) I do not understand the application of different measurements (Basic+, Premium, Premium+) to Room EQWizard. How REW is going to use the calibration files? E.g. is it going to influence phase measurements, waterfalls in REW? How?


Although both the EMM-6 and ECM8000 mics are marketed as "omnidirectional" microphones, they are only omnidirectional up to around 1-2 kHz. Above that, the frequency response of the mics will depend on the orientation of the mic with respect to the sound source (in particular the mics become less sensitive to higher frequencies as the mic is pointed away from the source). If you want to use the mic for loudspeaker measurements (where the mic is usually pointed directly at the speaker) or for low-frequency measurements (where the mics are truly omnidirectional) than the non-plus mics will work fine. 

However in room acoustics applications where the mic is picking up sound waves that are bouncing off the walls/ceiling/floor and arriving at the mic in arbitrary directions, the additional frequency response correction curves allow the user greater flexibility in using the mics. For room-correction/room acoustics applications, I typically recommend pointing the microphone straight up at the ceiling (with a slight tilt toward the main speakers) and using the 90-degree correction curve.



> 4) I have Tascam US-122, I hope it is still good for Dayton..


The Tascam will be fine.


----------



## michael123

thanks!
I just sent you a payment


----------



## Anechoic

Yep, I got the order. It will ship on Monday.


----------



## michael123

Herb,

given that at 5Hz, the error range is 10db, what is the usable frequency range of EMM-6? 
Also, taking humidity, temperature and other environmental factors, what would be the real-life precision of the calibrated EMM-6 across that range? Better than 3db? Better than 1db?
If I put the 'wind shield' on the mic, will it reflect the measurements? 

thanks


----------



## distox

Anechoic said:


> However in room acoustics applications where the mic is picking up sound waves that are bouncing off the walls/ceiling/floor and arriving at the mic in arbitrary directions, the additional frequency response correction curves allow the user greater flexibility in using the mics. For room-correction/room acoustics applications, I typically recommend pointing the microphone straight up at the ceiling (with a slight tilt toward the main speakers) and using the 90-degree correction curve.


Received your 8000 a couple of weeks back and I am having a blast using it. I am using the 90-degree correction curve and pointing the mic up with a slight tilt towards the speaker I am testing. I wonder what kind of inaccuracies in the higher frequencies, if any, are there with the interaction of a hard (low, about 7 feet) surface ceiling. Perhaps I should use the 45-degree curve instead?

-Tony


----------



## Anechoic

michael123 said:


> Herb,
> 
> given that at 5Hz, the error range is 10db, what is the usable frequency range of EMM-6?


I'm not sure I understand the question. With a correction curve, the usaable range is 5 Hz to 25 kHz. Without a correction curve, it's probably something like 80 Hz to 6 kHz.



> Also, taking humidity, temperature and other environmental factors, what would be the real-life precision of the calibrated EMM-6 across that range? Better than 3db? Better than 1db?


Environmental factors won't make a huge different unless you're using them in extremes (0 degrees F, 120 degrees F in the rain, etc). If you are using the mic in a standard comfortable environment (say 60-80 degrees F, 20-70% humidity), the differences in the mic response are on the order of tenths of decibiels.



> If I put the 'wind shield' on the mic, will it reflect the measurements?


The windscreen changes the response by about 0.5 to 1 dB above ~ 12 kHz.


----------



## Anechoic

distox said:


> Received your 8000 a couple of weeks back and I am having a blast using it. I am using the 90-degree correction curve and pointing the mic up with a slight tilt towards the speaker I am testing. I wonder what kind of inaccuracies in the higher frequencies, if any, are there with the interaction of a hard (low, about 7 feet) surface ceiling. Perhaps I should use the 45-degree curve instead?
> 
> -Tony


It's going to depend on how diffuse the sound field is in your room. If there's is a lot of energy coming from the ceiling, you might want to experiment with the 45 or 0 curves, but if the reflections are more random and coming in all directions, stick with the 90. 

Experiment, and then figure out what sounds better to your ears.


----------



## pepar

Anechoic said:


> It's going to depend on how diffuse the sound field is in your room. If there's is a lot of energy coming from the ceiling, you might want to experiment with the 45 or 0 curves, but if the reflections are more random and coming in all directions, stick with the 90.
> 
> Experiment, and then figure out what sounds better to your ears.


Is the orientation/cal used driven by the measurement being taken, e.g. 0° for the FR of an individual speaker, but 90° for decay/RT?

Jeff


----------



## distox

How do I know how diffuse my room is or how much energy is coming from the ceiling? I don't want to trust my ears first, I want to know what is correct, then I can tell my ears that it is correct and then choose what sounds good to me.


----------



## Anechoic

pepar said:


> Is the orientation/cal used driven by the measurement being taken, e.g. 0° for the FR of an individual speaker, but 90° for decay/RT?
> 
> Jeff


Yes.


----------



## Anechoic

distox said:


> How do I know how diffuse my room is or how much energy is coming from the ceiling? I don't want to trust my ears first, I want to know what is correct, then I can tell my ears that it is correct and then choose what sounds good to me.


Diffuse means that reflections have an equal probability of coming from any direction and it's a matter of how reflective the surfaces in your room are. If you have an empty four-sided with a floor and ceiling, and all 6 surfaces are acoustically "hard" you can consider that to be a diffuse environment (for the pendants out there, I'm simplifying) where reflections will be bouncing around between the surfaces in all directions. At the other extreme, if the four walls and floor are completely covered in absorptive material (thick carpet, thick curtains, etc) but the ceiling is still acoustically hard, most of the reflections in the room will be coming from the ceiling and the room is not diffuse. 

The 0-degree curve should be used when the mic is pointed in the direction of the sound source (or the reflection source if it's known and dominant). As the source of reflections become more spread out, you move toward the off-axis correction curves.


----------



## pepar

Anechoic said:


> (for the pendants out there, I'm simplifying)


You probably mean "pedantics", but then I'd be one if I pointed that out.


----------



## Anechoic

pepar said:


> You probably mean "pedantics", but then I'd be one if I pointed that out.


Touché


----------



## Anechoic

Hey all,

There have been a number of people trying to reach me by phone to ask questions either about my mic measurement service or the products I sell. The problem right now is that my schedule is extremely busy and likely to be so through mid-May at least which means the chances of you reaching me during normal business hours is basically zero and it's taking days for me to return calls.

For the moment, the best way to get an answer from me would be to post in this forum or send me an email directly, that way I can respond when I have small breaks. If you need to speak with me via phone, it would be helpful if I could speak to you during off hours (7pm to midnight EDT), so please let me know your availability if you leave a message. Oh, and be patient.

Thanks.


----------



## belmontjoe

Anechoic,

Just sent payment for a verified+ galaxy meter. Please calibrate from 5 Hz to 24kHz or as wide as you can go.

Thanks.


----------



## mtbdudex

I just ordered the Calibrated Behringer ECM8000 microphones Premium-Plus with Full size CD (I have a iMac and mini-CD does not work with it).

Your store said "Shipping estimates: Calibrated ECM8000 microphones are backordered through the end of the week."
Hopefully I can have it then week of 5/32/2011.

Background:
3 years ago I bought a Behringer ECM8000 , and used it with a generic Mic cal file downloaded from HTS.
It's just that I'm taking more measurememetns, both LFE for subs and also full 20-20khz for room acoustics and want to use a mic with a "real" cal file.

Thx for offering this at very reasonable price.
fwiw, I just held a Home Theatre meet at my home this past weekend:



























Including subwoofer shootout...


----------



## Anechoic

mtbdudex said:


> I just ordered the Calibrated Behringer ECM8000 microphones Premium-Plus with Full size CD (I have a iMac and mini-CD does not work with it).
> 
> Your store said "Shipping estimates: Calibrated ECM8000 microphones are backordered through the end of the week."
> Hopefully I can have it then week of 5/32/2011.


I managed to snag a few ECM8000s so I should be able to ship your order by the weekend. It's weird, it's like everyone (and I mean _everyone_) seems to be out of stock of ECM8000s right now.


----------



## mtbdudex

Anechoic said:


> I managed to snag a few ECM8000s so I should be able to ship your order by the weekend. It's weird, it's like everyone (and I mean _everyone_) seems to be out of stock of ECM8000s right now.


sweet! Thx for quick responding to this post.

out of stock = economy is improving? (finally!)


----------



## pepar

mtbdudex said:


> I just ordered the Calibrated Behringer ECM8000 microphones Premium-Plus with Full size CD (I have a iMac and mini-CD does not work with it).
> 
> Your store said "Shipping estimates: Calibrated ECM8000 microphones are backordered through the end of the week."
> Hopefully I can have it then week of *5/32/2011*.


Wow, that will be great if Herb gives you another day in the month.


----------



## michael123

pepar said:


> Wow, that will be great if Herb gives you another day in the month.


:rofl:


----------



## mtbdudex

pepar said:


> Wow, that will be great if Herb gives you another day in the month.





michael123 said:


> :rofl:


yea - my fat fingers!
Though in some alternate universe there could be 32 days in May???


----------



## Anechoic

mtbdudex said:


> sweet! Thx for quick responding to this post.
> 
> out of stock = economy is improving? (finally!)


If past indicators are true to form (my business seems to generally lead the economy, things crashed for me about a year before the housing & econonimic collapse) then yes! :T


----------



## Anechoic

pepar said:


> Wow, that will be great if Herb gives you another day in the month.


There's a reason they call me a miracle worker.


----------



## mtbdudex

Anechoic said:


> There's a reason they call me a miracle worker.


My mic came on 5/23!
Thx for fast service, raining today so instead of cutting the grass I'll be taking acoustic measurements.


----------



## mtbdudex

mtbdudex said:


> My mic came on 5/23!
> Thx for fast service, raining today so instead of cutting the grass I'll be taking acoustic measurements.


Well, last night I was able to at least test my 3 year old ECM8000 + generic HTS cal file vs the one I got from Cross-Spectrum Labs (CSL).

Good news is my prior measurements taken with the 3 year old set-up (in LFE) are pretty close to the CSL one.
I can say though my original generic ECM8000 HTS mic cal file (from mid-2008) is vastly different for corrections than the recent (Feb-2011 date?) HTS generic ECM8000 mic cal file.
I was comparing them Monday, I had kept the older one on my work laptop which I originally used for REW before trying REW5 on my iMac.

This is my IB sub at 2nd row 2nd seat position, no EQ, no Audyssey.

I did NOT adjust anything at all in REW5.
1st graph is "old" set up stock ECM8000 + generic HTS cal file, 
2nd graph is stock ECM8000 + new CSL cal file (to see the a vs b cal file diff before replacing with new mic), 
3rd graph is CSL calibrated ECM8000 with its specific cal file (the narrow band 90deg one, as I was taking LFE and pointed at the ceiling).









I then started taking many-many LFE measurements, comparing on my Denon A/V 4308CI Ext-In (sub alone) vs Aux In (RH/LH) diff xover points for mains(40/60/80 hz), diff Audyssey settings, etc.
You can get "lost" in doing that - in a fun/hobby way, even with putting notes in each measurement box which I do.

I won't plot those here, I will compare the Mid-Hi freq and plot those later as well though.

Again, thx CSL for quick turnaround, now I feel confident posting my graphs with a calibrated set-up.
Well, my RS digital sound level meter is not calibrated....so at worst I'm a few db off from a "datum" point of view, means not much unless you start "bragging" about how much spl your sub outputs, like some people in sub shoot out meets tend to do......(hey, were all friends still, right? Even if my sub kicks you subs ....I digress too much and will stop the banter...)


----------



## gjwaudio

*Just Ordered an EMM-6...*

Hi Herb

I just ordered a Premium+ EMM-6 from your website. Thanks for making these tools so affordable.

The ($5) joke is on me... after sending payment, I read about the HTS member discount you've offered.

Oh well... win some/ loose some. I'm really looking forward to getting the package in the mail.

Cheers,
Grant


----------



## Anechoic

*Re: Just Ordered an EMM-6...*



gjwaudio said:


> Hi Herb
> 
> I just ordered a Premium+ EMM-6 from your website. Thanks for making these tools so affordable.
> 
> The ($5) joke is on me... after sending payment, I read about the HTS member discount you've offered.
> 
> Oh well... win some/ loose some. I'm really looking forward to getting the package in the mail.
> 
> Cheers,
> Grant


No worries Grant, I got your back.

Just be advised that I'm still on the road so it will be about a week before your mic will ship


----------



## gjwaudio

*Re: Quick Delivery...*



Anechoic said:


> Just be advised that I'm still on the road so it will be about a week before your mic will ship


..ONLY a week ?? That's great. It will take me that long to figure out the REW program and how to make it sing and dance with my E-MU 0404 USB !

Thanks again Herb.

Cheers,
Grant

ps: THANK YOU for sending the five bucks back !


----------



## shap

Herb:

The Home Theater Shack site has calibration files for several SPL meters for use with the REW software. I decided against the CM-130 or the Radio Shack meters because neither meets IEC/ANSI ceritification. I bought the American Recorder SPL-8810 instead. This is the unit sold by the Guitar Center chain, and it is IEC certified. Of course, I did this not realizing that I would need a calibration file...

Have you perchance already done an REW calibration that is appropriate for this unit? If so, what would it take to get you to release that calibration file for posting here on the HTS site?

Regards,


shap


----------



## Anechoic

Hi Shap,

I haven't handled an SPL-8810 (it appears to be another Chinese OEM'd meter that several companies but a name plate on), so I don't have any calibration data to share, sorry.

From what I can can find, the SPL-8810 doesn't appear to have a line output, so I couldn't generate a calibration file for it anyway (at least without a lot of effort of manually checking various tones and plotting the freq response manually).


----------



## shap

Thanks for the prompt reply. Indeed it has no line out. More fool I for blindingly prioritizing certification, but it will probably do for my immediate purposes.

shap


----------



## gjwaudio

*EMM-6 Arrived Aug/11 - Thanks !*

Hi Herb

Just wanted to say Thank You for the quick delivery of my EMM-6 - it arrived last week (Aug. 11) safe and sound.

After a little head-scratching (and perhaps the odd, muted cuss word) I found a way to convert the .FRD calibration file to a .TXT file that Smaart7 would import. (open .FRD in Excel as space-delimited file/ delete column 1/ save as space-delimited .TXT file).

Funny how just renaming a copy of the original FRD file to TXT wouldn't work.

Now the real fun begins - working my room to assess & improve the acoustics (with REW & Smaart results to guide me).

Cheers,
Grant


----------



## mr.chill

*Re: EMM-6 Arrived Aug/11 - Thanks !*

Just want to say I used cross spectrum for my purchase of EMM-6 mic, they had great service and shipping and that was all the way to Norway 

Something to think about for the overseas customers


----------



## JMB

*Response to Dennis H. post #28, I believe*

Crossover design phase issues are relative; we are not using absolute phase to design the crossover. If you use the same microphone for all of your measurements, phase error should not be an issue. I believe that John K. has a post on the diyaudio.com site discussing this.

Jay


----------



## atomik

I've just received my mic calibrated by Herb ! 

Very good job and a quick shipment !


Now go and measure :flex:


----------



## cavchameleon

Herb's the best! Always very quick on delivery.


----------



## Anechoic

cavchameleon said:


> Herb's the best! Always very quick on delivery.


Well, not always (unfortunately). In fact I'm working up some mics and meters today that (when all is said and done) will have shipped out about 3-4 days after folks placed their orders. It comes down to a) do I have product in stock, and b) am I actually around to ship the products. Most times folks get lucky and I can move stuff fairly quickly. Some folks aren't nearly so lucky.

I'm hoping that in the next six to twelve months I can hire on some help and ship things more consistently. But for now, I'm trying my best.


----------



## Bandicoot

This might be a dumb question, but why isn't Cross Spectrum accredited by ANSI, ISO, etc?


----------



## Anechoic

Bandicoot said:


> This might be a dumb question, but why isn't Cross Spectrum accredited by ANSI, ISO, etc?


Going through that process would require a statistical analysis of my processes, calibrations of my measurement equipment made directly against NIST primary sources (as opposed to know where my equipment is calibrated by cal labs who in turn have their equipment calibrated against primary sources) and annual inspections/audits by certifying agencies, all of which I have to pay for. (it may also require that I set up a stable temperature/humidity environment but I'm not positive about that). I would also have higher insurance costs since any "accredited" mics/services I offer might be used by customers for multi-million dollar projects where measurement accuracy is paramount (environmental noise, concert hall renovations, etc) and if something went wrong I could be liable for heavy damages. I looked into it a while back, and the initial costs for all of this would be in the low mid-five figures (upgrading equipment, performing statistical analysis, upgrade my lab, etc), and the annual audit/inspection costs would be in the low-five figures. And that's just for ANSI/NVLAP (USA) accreditation, ISO and IEC have much stricter requirements. 

I could do it, but then the prices I would have to charge to recoup my costs would be similar to what other NIST-traceable labs have to spend: ~$150 for mic basic calibrations, $250+ for meter calibrations, etc. And at that point I would be directly competing with the few dozen other NIST-traceable labs around the country, and frankly there wouldn't be much point.

As the other parts of my business grow there is always the possibility that we may decide to gt NVLAP accreditation for other purposes and in that case I may let the mic biz free-ride on that accreddition, but that is a long ways off.


----------



## rgbit

News from Spain.

I'm just receiving a EMM6 Basic+ calibrated mic from CSL. Thanks Herb for your very good job. Only 7 days from payment. This is awesome speedy.

And mic appears great. Response curve is almost flat from 20 to 3Khz, and only a few crest of 4dB at 12.5 Khz. 
Cal files have a lot of intermediate values.
I am very happy and wanting to play with it.:nerd:


What I did not expect was the size of this micro. I have another Audyssey microphone, and is smaller. It seems that size does matter, even in the micro world:R

Again thanks Herb.:clap:


----------



## JimP

Is it possible to get the omnimic run through your calibration process and provide a correction file????


----------



## Anechoic

JimP said:


> Is it possible to get the omnimic run through your calibration process and provide a correction file????


There are two issues with calibrating the omnimic microphone:


2
The version I saw last year only worked with the Omnimic software. I've heard rumors that has changed with recent versions and that now the Omnimic shows up as a USB audio device - if that's true, than I can use it with my rig, otherwise I can't measure it (at least not easilly)
The diameter of the Omnimic mic I played with wasn't a standard diameter (I don't understand why mics manufacturers do this, the industry has standardized on 1/4", 3/8", 1/2", and 1" for decades now), which makes it harder for me to use in my low-frequency jig.

Assuming the mic does show up as a USB audio device, if someone wants to send one to me, I'll check it out.


----------



## Phillips

Anechoic said:


> Assuming the mic does show up as a USB audio device
> 
> 
> Where would it show up as USB Audio Device e.g. in REW?
> 
> Would it show up as USB Audio Device or possibly something else?


----------



## JimP

Anechoic said:


> There are two issues with calibrating the omnimic microphone:
> 
> 
> 2
> The version I saw last year only worked with the Omnimic software. I've heard rumors that has changed with recent versions and that now the Omnimic shows up as a USB audio device - if that's true, than I can use it with my rig, otherwise I can't measure it (at least not easilly)
> The diameter of the Omnimic mic I played with wasn't a standard diameter (I don't understand why mics manufacturers do this, the industry has standardized on 1/4", 3/8", 1/2", and 1" for decades now), which makes it harder for me to use in my low-frequency jig.
> 
> Assuming the mic does show up as a USB audio device, if someone wants to send one to me, I'll check it out.


Tell me where I should measure for the diameter of the mic. If its one of the standardize ones you listed, I'd be interested in sending it in for testing. It is the more recent version of the mic, not the original one.


----------



## Anechoic

JimP said:


> Tell me where I should measure for the diameter of the mic. If its one of the standardize ones you listed, I'd be interested in sending it in for testing. It is the more recent version of the mic, not the original one.


At the "business end" of the mic, at the capsule (it's just over 1/4-inch IIRC).


----------



## zheka

*I must be doing something wrong*

Hi Herb,

I am a recent owner of a calibrated Galaxy meter (verified +).


How reliable is calibration at the extremes supposed to be, specifically in the sub-10Hz region?

The reason I am asking is that results I am getting do not look realistic at all.

As you can see in the attached REW measurement snapshot I am getting 30dB jump from 70db at 15Hz to almost 100dB at 5Hz. Is it even theoretically possible?


The calibration file I amusing with REW is called "one_third_octave_band_response_random-incidence_C-wtd.frd". Is this correct file to use?

Here's the content of the file:


5 -30.49 0
6.3 -23.99 0
8 -19.35 0
10 -15.72 0
12.5 -12.62 0
16 -10.03 0
20 -7.9 0
25 -6.16 0
31.5 -4.74 0
40 -3.58 0
50 -2.66 0
63 -2.01 0
80 -1.65 0
100 -1.29 0
125 -1.04 0
160 -0.83 0
200 -0.73 0
250 -0.62 0
315 -0.5600000000000001 0
400 -0.48 0
500 -0.4 0
630 -0.28 0
800 -0.07000000000000001 0
1000 0 0
1250 -0.24 0
1600 -0.38 0
2000 0.44 0
2500 0.38 0
3150 0.36 0
4000 1.54 0
5000 2.55 0
6300 3.05 0
8000 2.2 0
10000 -0.19 0
12500 -5.07 0
16000 -10 0
20000 -15.2 0
25000 -19.97 0

I am not sure what it is that I am doing wrong. Any guidance you can offer is much appreciated.


----------



## Anechoic

*Re: I must be doing something wrong*



zheka said:


> Hi Herb,
> 
> I am a recent owner of a calibrated Galaxy meter (verified +).
> 
> 
> How reliable is calibration at the extremes supposed to be, specifically in the sub-10Hz region?
> 
> [snip]


I'm not an REW expert, but I would recommend trying the "narrow_band_response_random-incidence_C-wtd.frd" instead of the one-third octave band file. Also, do you have the meter set to C-weighting when you make the measurement? The data you quoted looks plausible - the Type 1 C-weighting value at 5 Hz is -25 dB, at 8 Hz -17.7 dB, at 10 Hz -14.3 dB, at 12.5 Hz -11.3 so it's certainly in the right ballpark.

What is the serial number of your meter?


----------



## zheka

*Re: I must be doing something wrong*

SN 110508226

I am using C weighting and response slow.

I will try the narrow band cal file and report back.

Thank you very much!


----------



## zheka

*Re: I must be doing something wrong*

results using both cal files look very close to me.


----------



## Anechoic

*Re: I must be doing something wrong*



zheka said:


> results using both cal files look very close to me.


The cal files for your meter look kosher. Try checking in the REW forum to make sure there isn't something wrong with the software settings. If that's not it, maybe your meter went bad - if the REW forum folks can't clear it up, you can ship the meter back to me and I can take another look.

(also, did you take advantage of the HTS discount for your meter?)


----------



## zheka

*Re: I must be doing something wrong*



Anechoic said:


> The cal files for your meter look kosher. Try checking in the REW forum to make sure there isn't something wrong with the software settings. If that's not it, maybe your meter went bad - if the REW forum folks can't clear it up, you can ship the meter back to me and I can take another look.


sounds good, thank you very much.


Anechoic said:


> (also, did you take advantage of the HTS discount for your meter?)


no, I did not


----------



## Anechoic

*Re: I must be doing something wrong*



zheka said:


> no, I did not


Check your PMs.


----------



## zheka

*Re: I must be doing something wrong*



Anechoic said:


> Check your PMs.


Thank you!


----------



## zheka

*Re: I must be doing something wrong*



Anechoic said:


> The cal files for your meter look kosher. Try checking in the REW forum to make sure there isn't something wrong with the software settings.


I tried RS meter with generic calibration and got the same weirdness. This rules out the bad meter theory. I am taking this to the REW forum.

Thank you for all the help


----------



## Anechoic

A couple updates to calibrated mic/meter sales:


I've started shipping calibration files on 128k USB thumb drives rather than mini-CD's. For those concern about virii that might have been infected the drives at the factories, my script reformats the drive prior to copying over the cal files so that should mitigate the danger. 
Meter/mic shipments will be backordered for a couple weeks while I send my reference microphone to calibration lab for its biennial NIST-traceable calibration. I have a few mics and 1 meter in stock, but after that it may be a week or so before shipments resume. 
Also, after careful consideration I've decided to drop the Basic and Premium options and to just sell Basic+ & Premium+ mics. I sell something like 10 Basic mics and 1-2(!) Premium mics per year, so for me the extra options (and having to spend time explaining those options) just isn't worth it.


----------



## Doctor X

Hi Anechoic,

I'm interested in the Dayton mic. You mentioned on another page that the Dayton mic was flatter and more reliable than the Behringer. My question is, does it really matter if there are variations between these models if you are going to apply a correction file to correct the response? 

So in other words, why spend $200-300 on a mic, when a cheapie, relatively speaking with a correction file can get close or similar results? Just need to understand the need for expensive mics.

All I want is to measure the room, set speaker and subwoofer levels correctly (currently using a Radioshack meter) and I want my measurements to be repeatable, so I need some accuracy. I've never used REW, but I'm almost made up my mind on the Dayton mic (if you could please tell me whether it should or needs to be calibrated) with Tascam US-122 MKII (USB sound card with phantom power).


----------



## Anechoic

Vaughan100 said:


> Hi Anechoic,
> 
> I'm interested in the Dayton mic. You mentioned on another page that the Dayton mic was flatter and more reliable than the Behringer. My question is, does it really matter if there are variations between these models if you are going to apply a correction file to correct the response?


In theory it shouldn't matter. However having to make large adjustements (especially at the lower frequencies) _may_ cause distortion problems, so if folks want to minimize and potential problems, they should go with the mics that are flatter out-of-the-box (typically the Daytons, although that's not as true now as it was a few years ago).



> So in other words, why spend $200-300 on a mic, when a cheapie, relatively speaking with a correction file can get close or similar results? Just need to understand the need for expensive mics.


Flatter (meaning: more expensive) mics allow you some flexibility, the most important being that you can use it with any analyzer without needing a calibration file. The more expensive mics also have other features such as lower noise floors, higher SPL limits, better insensitivity to temperature & humidity variations, higher sensitivities and so on.


----------



## Doctor X

Thanks for answering my question Anechoic. So in your opinion, for measuring frequency response in the room, would you choose the Dayton over the Behringer and would you still have it calibrated, or would you rather rely on a correction file? Just trying to make up my mind which is better for the application.


----------



## Anechoic

Vaughan100 said:


> Thanks for answering my question Anechoic. So in your opinion, for measuring frequency response in the room, would you choose the Dayton over the Behringer and would you still have it calibrated, or would you rather rely on a correction file? Just trying to make up my mind which is better for the application.


(keeping in mind that I'm selling calibrated Daytons and Behringers and it's in my interest to convince you to buy my mics rather than buying them from others)

I would wholeheartedly recommend *against* buying an uncalibrated Behringer ECM8000. There is too much variability - you never know when you may wind up getting an ECM8000 with a frequency-response like this. Not to mention that a good percentage of ECM8000's have problems out of the box.

The Dayton mics straight from PE come with a 20Hz - 20kHz calibration file. I think my cal files are more accurate, but it you're looking to save some money, the factory cal curve is certainly good enough. 

The mics I sell come with 90-degree correction curves and for room measurements I recommending pointing the mic at the ceiling (tilted slightly toward front speakers) and using the 90-degree correction curve. The off-the-shelf Dayton only comes with 0-degree correction curves, which can be useful might might require some experimentation for room acoustics purposes. My calibrations are also performed from 5Hz to 25 kHz, if you care about the lower bass, the factory Dayton curve may not be sufficient.


----------



## Doctor X

Thank you for the in-depth reply! I don't require 5 Hz measurements .. and I'm not a speaker designer, just want to measure my room, check before and after and make sure the results are accurate. 

I sent you a PM. Thanks.


----------



## Anechoic

Vaughan100 said:


> Thank you for the in-depth reply! I don't require 5 Hz measurements .. and I'm not a speaker designer, just want to measure my room, check before and after and make sure the results are accurate.
> 
> I sent you a PM. Thanks.


It may be that the factory Daytons from PE will work for you, especially if you're just making before & after comparisons.


----------



## Doctor X

Thanks again. Will keep in touch with you concerning the mic, as I think that's the one to go for.


----------



## rogerv

I want to add my thanks and appreciation to the quality service that Cross-Spectrum is providing. I had read some threads a while back discussing the Behringer mics and their use with REW, and the need to have a calibration file. I filed that away for future use and finally got around to ordering one the other day. I provided my HTS user i.d. on the PayPal order. Within a few minutes, Herb emailed me to let me know that the HTS discount doesn't apply to the Behringer's, and asked me whether I wanted to convert the order to a Dayton. 

Since I was a little behind the curve in terms of my research, we exchanged some additional emails discussing the relative merits of each. That discussion convinced me that the Dayton was probably better technically, and a better deal financially. Herb changed the order the order as a result. I think that was fantastic.

Thanks for the great service. :T It's something that I greatly appreciate. I would recommend Cross Spectrum's service wholeheartedly. 

I'm looking forward to another round of REW measurements and tweaking in the next couple of months. It will be interesting to compare results with the newer more accurate equipment with what I got with the Radio Shack meter.

Rog


----------



## Ngtybear

I would like to upgrade my current RS mic and built in PC audio for a USB external with a Calibrated EMM-6 from Herb. 

I am using an IB for sub and would like to be capable of messuring down to 5hz hopefully. Does someone have a recomendation for an external (USB) sound device with a midi interface if at all possible which can handle down that low? OS is Windows 7 or Linux. 

Thank you....


----------



## aackthpt

Ngtybear said:


> I am using an IB for sub and would like to be capable of messuring down to 5hz hopefully. Does someone have a recomendation for an external (USB) sound device with a midi interface if at all possible which can handle down that low? OS is Windows 7 or Linux.


Tascam US-122/144mkII are popular, have MIDI, and quite flat--look to be down about 3dB at 5 Hz. I may finally buy one as there is a $10 rebate at most music retailers at the moment (and I'm employed which I was not when I started using REW, LOL). You can find the calibration curve for this interface right here.


----------



## Phillips

JimP said:


> Is it possible to get the omnimic run through your calibration process and provide a correction file????


Hi Jimp did you get the Omnimic re-calibrated?

Which version do you own?


----------



## JimP

No, I didn't.
Got sidetracked with changing out my display and calibrating video.
Not sure If I'll get the Omnimic recalibrated as I was only planning to use it on REW. I can use it on the omnimic software and import the settings which gets me there...I think.


----------



## Phillips

JimP said:


> No, I didn't.
> Got sidetracked with changing out my display and calibrating video.
> Not sure If I'll get the Omnimic recalibrated as I was only planning to use it on REW. I can use it on the omnimic software and import the settings which gets me there...I think.



Thanks Jimp

Did you have any feedback (after) from Cross-Spectrum about being able to calibrate your mic?

Which version Mic do you have?


----------



## roognation

Hey, great forum. Thanks for sharing. Now for my first post: I am curious if someone could speak to the sensitivity of the Dayton microphone, I am hoping to do some very low-noise measurements and wanted to see if there was a suitable mic that wouldn't break the bank. I was hoping to get in to the 20 dBSPL range, but not sure if that is realistic. Anyone care to comment?

Also, I was looking at using the Motu 4Pre as my Mic -> USB solution. Any users care to comment?

Really like fooling around with REW; thanks for that! I hope to learn more in the coming months.

Thanks!

EDIT: can REW do simultaneous multi-mic RTA? The Motu 4pre has 4 mic inputs...would be nice.


----------



## Anechoic

roognation said:


> I was hoping to get in to the 20 dBSPL range, but not sure if that is realistic. Anyone care to comment?


Yeah, you're not going to get a 20 dB noise floor without spending some serious coin. The noise floor on Dayton mics range from 30 to 35 dBA (note the "A") and maybe 40-45 dB. Behringer mics range from around 35 to 40 dBA, perhaps 45-50 dB linear.

To put this in perspective, my quietest ANSI/IEC class 1 mics (1/2-inch BSWA MP201 & PCB 308B02) have noise floors around 15 dBA, 20 dB linear. To get much lower than that on a measurement mic, expect to pay well over $1,000 for a 1-inch B&K/Gras/etc capsule + pre-amp and power supply.


----------



## Phillips

Hi 
Has anyone had their Omnimic re-calibrated, is it possible?


----------



## aackthpt

roognation said:


> I am hoping to do some very low-noise measurements and wanted to see if there was a suitable mic that wouldn't break the bank. I was hoping to get in to the 20 dBSPL range, but not sure if that is realistic. Anyone care to comment?


I asked similar questions in this thread and didn't get any great answers. However I've just done a bit more searching and perhaps can be a bit more specific than anechoic was above.

Earthworks (least expensive model M23 ~$450) is spec'd at 22 dBA self noise.
DPA 4006A is spec'd at 15dBA typical 17 dBA max (though they also list 27-29 dB per ITU-R .468-4, I'm not sure what that means at the moment)-this is a $1925 mic. (!)
B&K 4955 is spec'd at <6.5dBA self-noise, but their (and, it appears, THE) ultimate setup is 4179+2660pre, the 2179 is spec'd for -5.5dBA. But this stuff isn't available at retail so is probably "If you have to ask, you can't afford it" sort of pricing.
The GRAS that anechoic mentioned is here. I haven't looked at it in any detail.
ACO stuff looks to be here and here, I again haven't reviewed it or looked for pricing (would be glad to see it if you look into it).
Looks like you can get the "SoundFirst SF101a" from http://www.testmic.com/ at 13dBA for $890, they say the SF111a should be ~10dBA for $1415. Also interesting what that site says of their Josephson mic: "This is the mic that many manufacturers copied the body from, but not the performance." It does indeed look much like the Behringer and Dayton mics most of us 'round here use.
I also found LinearX M53 for $350 at 18 dBA.
There's also some stuff from Scantek that I haven't looked at much.

So predictably the costs appear to be pretty well exponentially increasing the lower the desired noise floor beyond an "average" level.

There was also some discussion of preamp noise levels there, however it looks to me that they are all rated in dBFS so as long as you don't have a lot of dynamic range in the measurement I'm guessing reducing the input gain will mitigate that problem.


----------



## Anechoic

aackthpt said:


> DPA 4006A is spec'd at 15dBA typical 17 dBA max (though they also list 27-29 dB per ITU-R .468-4, I'm not sure what that means at the moment)-this is a $1925 mic. (!)


ITU-R .468 is another frequency weighting curve, similar to A-weighting.



> B&K 4955 is spec'd at <6.5dBA self-noise, but their (and, it appears, THE) ultimate setup is 4179+2660pre, the 2179 is spec'd for -5.5dBA. But this stuff isn't available at retail so is probably "If you have to ask, you can't afford it" sort of pricing.


Yep. My old firm has that setup, it's used for measuring noise levels at very remote locations where there are no man-made noise sources for dozens of miles. I don't remember the pricing, but I'm guessing it's at least in the $2,500 range. It was only used for very special occasions .



> ACO stuff looks to be here and here, I again haven't reviewed it or looked for pricing (would be glad to see it if you look into it).


I have the ACO Pacific price list, current as of last winter, if someone has a specific question, let me know. I own the 7052, the noise floor for my capsule is in the low 20's, which is typical for a Type 2 mic.

There's also the used-equipment inventory at Modal Shop.



> I also found LinearX M53 for $350 at 18 dBA.


That's a really good price if that spec actually holds up. 



> There's also some stuff from Scantek that I haven't looked at much.


That's where I got my BSWA MP201 from, the 1/2 inch Class 1 mics will all have noise floors in the 15-17 dBA range. They also off Class 0 mics that probably have lower noise floors (probably not lower than around 8 dBA though), but you don't want to know that pricing.



> There was also some discussion of preamp noise levels there, however it looks to me that they are all rated in dBFS so as long as you don't have a lot of dynamic range in the measurement I'm guessing reducing the input gain will mitigate that problem.


With regard to IEC/ANSI-rated equipment, the mic usually determines the noise floor moreso than the pre-amp unless the mic floor is really quiet (~5 dBA or lower).

Also remember that the noise floor of the mic will have to be at least 8 to 10 dB lower than the noise level to be measured, so to measure noise levels at 20 dBA, the mic will need a noise floor of 8 to 10 dBA.


----------



## aackthpt

Anechoic said:


> There's also the used-equipment inventory at Modal Shop.


Neat, love used equipment sources--good call, thanks.



> Also remember that the noise floor of the mic will have to be at least 8 to 10 dB lower than the noise level to be measured, so to measure noise levels at 20 dBA, the mic will need a noise floor of 8 to 10 dBA.


OK so to verify RC30, the maximum acceptable noise level per the Nyal/Hedbeck paper, because the A curve is ~0dB at 4k, and the RC curve is at 20 there, to be able to verify that requirement you'd need a mic with 10-12 dBA noise floor? Am I incorrect because the RC measurement is in an octave band which will contain less energy and therefore correspond to a higher dBA noise floor requirement? I note that the chart in the link shows 40 dBA as the equivalent sound level of RC30--if true that would be a significantly easier requirement to meet (maybe I need to just read the ARTA manual finally, LOL).

With the LinearX mic you do have to pay extra for the clamshell case and mic clip. LOL. It also looks like it requires +9V so you have to build special cables rather than simply being able to use the phantom power on the common interfaces....


----------



## Anechoic

aackthpt said:


> OK so to verify RC30, the maximum acceptable noise level per the Nyal/Hedbeck paper, because the A curve is ~0dB at 4k, and the RC curve is at 20 there, to be able to verify that requirement you'd need a mic with 10-12 dBA noise floor? Am I incorrect because the RC measurement is in an octave band which will contain less energy and therefore correspond to a higher dBA noise floor requirement? I note that the chart in the link shows 40 dBA as the equivalent sound level of RC30--if true that would be a significantly easier requirement to meet (maybe I need to just read the ARTA manual finally, LOL).


This is a hard question to answer since RC (as well as NC and NCB) are defined in the frequency domain, so the applicability of any particular mike will really depend on the specific characteristics of the mic as well as the spectrum of the background noise. The overall equivalent A-weighted level can very wildly for the same RC level. For example, if the background noise was a pure tone at 31.5 Hz at 60 dB, the A-weighted equivalent for that tone is 20 dBA, but it would still exceed RC 30. 

All I can really say for sure is that microphone self-noise typically follows a 1/f pattern, so the self-noise may be more of a problem in low-frequency applications compared to mid- and high-frequency applications.


----------



## aackthpt

Anechoic said:


> This is a hard question to answer since RC (as well as NC and NCB) are defined in the frequency domain


OK, I can see your point here.

Pros at this can't all just buy the ultimate B&K rig I'd imagine (although Nyal uses some type of B&K rig, don't know if it's "ultimate" -- but B&K's app note on KYDG says KYDG balked at the cost). And I wouldn't think they would all just buy a mic advertised for this use and hope. If there isn't a way to pre-calculate it, do pros do a test that verifies the self-noise of their chain?



> All I can really say for sure is that microphone self-noise typically follows a 1/f pattern, so the self-noise may be more of a problem in low-frequency applications compared to mid- and high-frequency applications.


That seems promising, given that's effectively the shape of the allowed noise curves under most systems--especially RC. Thanks for that, I was wondering what the typical spectral shape looks like since I don't think anyone's mentioned it yet.


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## Anechoic

aackthpt said:


> OK, I can see your point here.
> 
> Pros at this can't all just buy the ultimate B&K rig I'd imagine (although Nyal uses some type of B&K rig, don't know if it's "ultimate" -- but B&K's app note on KYDG says KYDG balked at the cost). And I wouldn't think they would all just buy a mic advertised for this use and hope. If there isn't a way to pre-calculate it, do pros do a test that verifies the self-noise of their chain?


Yes. The simplest way is to get a dummy mic that matches the capacitance of the microphone you're going to use (something like this) and determine the equivalent noise floor. The more difficult method is to put the mic in a quiet environment and determine the noise floor directly. For my noise floor measurements, I have an old hearing-aid chamber that I bought off eBay a few years ago, that provides isolation of about 15-20 dB. Using it in my basement at night, I can get levels down to below 16 dBA (that's as low as my Larson-Davis, NTi and Sencore meters go with the mics I own). Building a heavier-duty enclosure with mounting it on a vibration-isolated platform, you might be able to approach 5 dBA or so. And of course there are anechoic chambers such as the Orfield facility with free-field background levels down to 0 dBA or below.



> That seems promising, given that's effectively the shape of the allowed noise curves under most systems--especially RC. Thanks for that, I was wondering what the typical spectral shape looks like since I don't think anyone's mentioned it yet.


If the noise source is a properly installed and balanced HVAC noise, the spectrum should resemble NC/NCB/RC curves. If the HVAC is improperly installed (unbalanced, or generating structure-borne noise) or it's a different source (outdoor traffic for example), the spectrum would change accordingly.


----------



## aackthpt

Anechoic said:


> Yes. The simplest way is to get a dummy mic that matches the capacitance of the microphone you're going to use


OK gotcha. Now this is starting to make sense. One more question, that page says "The method is not usable for measurement of the thermodynamic noise of the microphone cartridge." I presume this is based on the presumption that is an inconsequential contributor to the total self-noise of the chain (so the preamp is virtually all of the self-noise), and that there are studies somewhere substantiating it; is this correct? Or is it just sort of standard practice so no one worries about it anymore?



> For my noise floor measurements, I have an old hearing-aid chamber


Ahh, makes sense again. I saw a page somewhere discussing mic testing in a chamber, and I'd envisioned it before that. That there's a commercial product only makes sense.



> If the noise source is a properly installed and balanced HVAC noise, the spectrum should resemble NC/NCB/RC curves.


LOL, I knew that--I was wondering about the spectrum of the self-noise, not the spectrum of the typical expected environmental noise/etc. I should have been more specific.

Thanks for your insights here.


----------



## Anechoic

aackthpt said:


> OK gotcha. Now this is starting to make sense. One more question, that page says "The method is not usable for measurement of the thermodynamic noise of the microphone cartridge." I presume this is based on the presumption that is an inconsequential contributor to the total self-noise of the chain (so the preamp is virtually all of the self-noise), and that there are studies somewhere substantiating it; is this correct? Or is it just sort of standard practice so no one worries about it anymore?


Good question. Consulting my copy of Beranek's _Acoustical Measurements_, the self noise (in rms volts) caused by thermal fluctuations can be calculated using the equation 

e = sqrt (4 * k * T * R)

where k= Boltzmann gas constant of 1.37e-23, T= absolute temperature in Kelvin, R is the resistive component of the mic impedance (usually in the range of a couple of hundred ohms)

For a temperature of 296 K (room temp), R set to 1000 ohms, that gives an rms voltage of 4e-9 volts. For a 10 mV/Pa mic, that corresponds to an RMS pressure of 4e-7 Pa, which is about -33 dB. So it looks like it is an inconsequential contributor.



> Ahh, makes sense again. I saw a page somewhere discussing mic testing in a chamber, and I'd envisioned it before that. That there's a commercial product only makes sense.


You could just as easily build one using heavy wood and foam, it was just easier for me to buy it on eBay, since I don't think I paid more than $50 for it.



> LOL, I knew that--I was wondering about the spectrum of the self-noise, not the spectrum of the typical expected environmental noise/etc. I should have been more specific.


Oops. 

Here are some noise floor plots using an NTI XL2 and a dummy mic:


























Here are some noise floor plots using an NTI XL2 and a PCB mic in my chamber (note the different y-axis scale):


























The chamber measurements were made in the middle of the day, so they're probably a few dB high because of outdoor activity.


----------



## aackthpt

Anechoic said:


> So it looks like it is an inconsequential contributor.


Does this only go for pro-style mics, which I presume don't have active components in the capsule? Because there are lots of pages about the Panasonic WM-61a (supposed that was/is used in the ECM8000) that supposedly has a FET in it, the (infamous) Linkwitz mod, etc. 



> You could just as easily build one using heavy wood and foam, it was just easier for me to buy it on eBay, since I don't think I paid more than $50 for it.


Fair enough. There's one there now too but it's $150 start price for the auction. Not that I really need such a thing, LOL.

Thanks for the plots, I always like data.


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## Anechoic

aackthpt said:


> Does this only go for pro-style mics, which I presume don't have active components in the capsule? Because there are lots of pages about the Panasonic WM-61a (supposed that was/is used in the ECM8000) that supposedly has a FET in it, the (infamous) Linkwitz mod, etc.


That's a good point about the FET, pro measurement mic capsules (AFAICT) are relativey "pure" with just the diaphragm and a charged backplate. The pre-amps obviously have more electronics, but they are designed to be low noise (pre-amps go for about $300 - $500 new, $50-$150 used, plus you need a power supply).

The noise floor for WM-61a's that I've measured have been around 25 dBA.



> Fair enough. There's one there now too but it's $150 start price for the auction. Not that I really need such a thing, LOL.


I'm guessing that one actually works, unlike the one I bought.

Another option would be to check it a local cabinet maker, furniture maker or woodshop. A local cabinet maker made the enclosure of my reference speaker (12-inch cube) using scrap pieces of 1/2-inch mdf for $50.


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## aackthpt

Let me just say thank you very much for all your responses. They were highly enlightening for me and I think I understand the basics of this area much better now.

I did think of one more pertinent question... for a hobbyist wanting to measure the background (or projector, pro amp, etc) noise in their HT, do you think (for absolute level) comparison to RS meter (eg I have the old analog model) is sufficient or would I need to consider getting a meter with calibration? Would it be better to just invest in an SPL calibrator? I read that meters are better than they used to be and that calibrators are a throwback (and double check) today.


----------



## Anechoic

aackthpt said:


> I did think of one more pertinent question... for a hobbyist wanting to measure the background (or projector, pro amp, etc) noise in their HT, do you think (for absolute level) comparison to RS meter (eg I have the old analog model) is sufficient or would I need to consider getting a meter with calibration? Would it be better to just invest in an SPL calibrator? I read that meters are better than they used to be and that calibrators are a throwback (and double check) today.


If you're just looking at overall dBA or dBC levels, the Radio Shack meter isn't actually too bad. However, if you're trying to get levels at particular frequencies or particular frequency bands, stay away from the RS meters as their frequency responses are all over the place, especially above 1 kHz. 

Now with card to getting a meter with or without calibration - if you get a meter that is ANSI or IEC rated, generally the frequency response will fall within the rated tolerances even if you don't have a specific calibration curve for the meter. Just keep in mind the the Type 2/Class 2 tolerances are +/- 1.5 dB from 100 to 1250 Hz, +/- 2 dB from 40-80 Hz & 1600-2000 Hz, and become higher beyond those limits (up to +5/-infinity below 20 Hz and above 8000 Hz) so it's up to you to decide if those tolerances are acceptable.

As for getting an acoustical calibrator, again that depends on how precise you are trying to get. Out-of-the-box most ANSI/IEC rated meters (even the cheap ones) will be within 3-4 dB of the absolute level - most of the differences are do to unit-to-unit setting variations as well as factors that can affect ambient air pressures (such as elevation). If you want more precision, an acoustical calibrator is a good investment, you can get decent Type 2 calibrators from Amazon. A calibrator is also good for checking the meter if you drop it, which might shift the calibration set screw found on lower end meters.

Again remember that the noise floor for your meter needs to be at least 8-10 dB lower than the level you're trying to measure. The noise floor on Type 2 meters (including the Galaxy ones I sell) are around 30 dBA, so if you're trying to measure noise from quiet equipment, you might have difficulty with those meters.


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## Sailor_Ernie

Herb,
I have a pair of B&K 4007’s with the original factory Calibration charts, dated Jan. 1993. 
I’m considering having you calibrate one of them for me so I will have a cal. file for REW.
Could you please advise of the current pricing and approximate return shipping cost to Canada.
I trust you didn’t indulge in too much turkey today. Thanks for all your comments and Cheers.


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## Anechoic

Sailor_Ernie said:


> Herb,
> I have a pair of B&K 4007’s with the original factory Calibration charts, dated Jan. 1993.
> I’m considering having you calibrate one of them for me so I will have a cal. file for REW.
> Could you please advise of the current pricing and approximate return shipping cost to Canada.
> I trust you didn’t indulge in too much turkey today. Thanks for all your comments and Cheers.


A basic calibration (on-axis frequency response only) is $55 per mic. Shipping is included for US customers, for Canada, I'll have to ask for $20 USD shipping. Two off-axis angles, polar response and sensitvity/noise floor are available for $10 extra each. $75 per mic gets you everything. Fee is payable with check or through PayPal. If you want to proceed, PM me and I'll send you shipping info.

edit: one thing to mention is that during my last job, we found that B&K mics were extremely fragile and we had around a 8-10 of them fail on us over the course of my tenure there (8 years). Depending on much you value these mics, you may want to consider if you really want to subject them to international shipping (or at least insure them).


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## Sailor_Ernie

Anechoic said:


> edit: one thing to mention is that during my last job, we found that B&K mics were extremely fragile and we had around a 8-10 of them fail on us over the course of my tenure there (8 years). Depending on much you value these mics, you may want to consider if you really want to subject them to international shipping (or at least insure them).


Thanks for the quick reply. I will have to consider your concern about possible damage and get back to you.


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## Anechoic

Anechoic said:


> edit: one thing to mention is that during my last job, we found that B&K mics were extremely fragile and we had around a 8-10 of them fail on us over the course of my tenure there (8 years). Depending on much you value these mics, you may want to consider if you really want to subject them to international shipping (or at least insure them).


As an FYI in case anyone is interested, we eventually phased out the B&K mics for GRAS microphones and those things were about as bulletproof as you could get - I think we lost one during my tenure. My 7-year old ACO Pacific 7052 has also been a champion, it gets used nearly every day, and its last calibration (last June) showed no problems.


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## Doctor X

I posted elsewhere, but if I have my CM-140 calibrated would it give me better results when setting speaker and subwoofer levels with pink noise? Or would the standard CM-140 suffice for that role? My Radioshack meter was stolen, so I need another meter, but if the Cross Spectrum calibration offers better results then I would do it. Just need some advice here.


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## aackthpt

Vaughan100 said:


> I posted elsewhere, but if I have my CM-140 calibrated would it give me better results when setting speaker and subwoofer levels with pink noise? Or would the standard CM-140 suffice for that role? My Radioshack meter was stolen, so I need another meter, but if the Cross Spectrum calibration offers better results then I would do it. Just need some advice here.


Technically the noise a processor emits for the manual level setting operation is white noise, and no a "calibrated" meter will not really give better results. That's because (a) for a meter calibration does not change the frequency balance the meter senses, it only corrects the absolute level it reads and (b) the absolute level is not important when setting the channel levels as the most important thing about them is the relative level. That is unless you really care that 0 is "reference level"... but very few people care to listen at reference level and there's no reason to attempt to lose your hearing. You are best off considering the volume setting during regular listening to only be a relative indication and not worry about what the number is; just set it "by ear" to a level that allows you to hear most of the detail in a soundtrack while being comfortable.


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## Anechoic

aackthpt said:


> Technically the noise a processor emits for the manual level setting operation is white noise, and no a "calibrated" meter will not really give better results. That's because (a) for a meter calibration does not change the frequency balance the meter senses, it only corrects the absolute level it reads and (b) the absolute level is not important when setting the channel levels as the most important thing about them is the relative level. That is unless you really care that 0 is "reference level"... but very few people care to listen at reference level and there's no reason to attempt to lose your hearing. You are best off considering the volume setting during regular listening to only be a relative indication and not worry about what the number is; just set it "by ear" to a level that allows you to hear most of the detail in a soundtrack while being comfortable.


It depends on how Vaughan100 is using the meter and the type of "calibration" being discussed. In terms of just a simple level calibration (my Verified products) and the meter being used as a stand-alone device, aackthpt's post is entirely correct. My "Verified+" offer frequency correction curves in narrow-band and 1/3 octave band levels. The 1/3 octave band correction levels can be used to correct the response of the meter when used with pink noise (although doing it manually would be tedious). If the meter is connected to a reliable sound card (or a decent computer-on board audio), the narrow-band correction files can be used with programs like REW etc to correct for the meter response. 

The calibrations do provide increased accuracy, but the difference is not as dramatic as it is for microphones like the ECM8000.


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## aackthpt

Anechoic said:


> In terms of just a simple level calibration (my Verified products) and the meter being used as a stand-alone device


Thanks for the clarification; I was indeed making that assumption. I would never think of someone hooking a meter up to REW when just setting levels (seems like unnecessary effort) but I also guess I hadn't considered that someone might be setting levels between mains and sub by using sweeps or tones+RTA window, in which case calibration would definitely be desirable!

Oh well, we all know what "to assume" does.... :whistling:


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## Doctor X

I'm talking about setting levels to 75 dB for each speaker and subwoofer. Would the standard CM-140 suffice or would the calibrate (verified) offer better results? The whole reason for NOT using my ears is because the ears are usually unreliable for setting levels, hence why I need to verify what the levels are.

I just need clarification on the meter thing. If I'm burning cash for no reason then I'll just stick to the standard CM-140. I won't be using REW, just the internal pink noise in the AVR.


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## Anechoic

Vaughan100 said:


> I'm talking about setting levels to 75 dB for each speaker and subwoofer. Would the standard CM-140 suffice or would the calibrate (verified) offer better results? The whole reason for NOT using my ears is because the ears are usually unreliable for setting levels, hence why I need to verify what the levels are.
> 
> I just need clarification on the meter thing. If I'm burning cash for no reason then I'll just stick to the standard CM-140. I won't be using REW, just the internal pink noise in the AVR.


The standard uncalibrated CM-140 tends to be within 1-3 dB of the actual SPL value out-of-the-box. That said, the verified meters I sell have been adjusted to the correct value and sell for about the same price you can get a CM-140 elsewhere (and a little cheaper with the HTS discount).


----------



## Doctor X

Anechoic said:


> The standard uncalibrated CM-140 tends to be within 1-3 dB of the actual SPL value out-of-the-box. That said, the verified meters I sell have been adjusted to the correct value and sell for about the same price you can get a CM-140 elsewhere (and a little cheaper with the HTS discount).


So in other words, 75 dB on the CM-140 might be 77-78 dB in reality?


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## Anechoic

Vaughan100 said:


> So in other words, 75 dB on the CM-140 might be 77-78 dB in reality?


72-78 dB, yes. Most are within +/- 1.5 dB or so, but I've seen a few outliers.


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## Doctor X

Just a question, as I heard a member talk about a calibrated CM-140 in the UMM-6 thread (not sure if was referring to the cross-spectrum calibration or not) but :

"i was previously considering the calibrated galaxy cm-140 (just to skip phantom power and mic pre) but after looking at the posted calibration result i decided to cancel. the meter have too much attenuation at the low frequency that it's not exactly precise anymore. -6db down at 20hz, -12db down at 10hz and -22db down at 5hz. it's only flat to 100hz."

Is this true? I just received my CM-140 calibrated by cross-spectrum. Is it still inaccurate? I'm confused by the above comments.


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## Anechoic

The CM-140 is a sound level meter that only has A- and C-weighted settings. Both of those weightings roll off the high and low frequencies, with the A-weighting setting producding sharper rolloff, but C-weighting is still down 14 dB at 10 Hz. The correction curves I ship with those meters (in theory) will correct for those extreme rolloffs and flatten the response. However boosting the levels that much (as much as 25 dB at 5 Hz) can create distortion problems similar to what you would get if you boosted the level of a graphic equalizer by 20 dB. That's the potential issue one might have to deal with. 

The meter and the calibration aren't inaccurate, it's just a matter to the degree that it needs to be corrected to produce a flat response.


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## Doctor X

How do I know how much you boosted my curve by so that I know that there is low distortion as opposed to a lot of distortion?

I'm just trying to understand this. You mention distortion, but how do I know that my meter doesn't have gross distortion due to huge correction? What does that mean for me? How does this distortion influence the results? 

I'm not clued up, clearly, but I wasn't aware there would be potential problems. I just thought I would get my meter calibrated for accurate results. Please try to clarify these things for me ...


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## Anechoic

Are you the Vaughan from SA? If so, you got a "Verified" meter, so I didn't provide you with a correction curve (as opposed to the "Verified+" meters which are provided with correction curves). If you use your meter as a microphone with a computer program (REW, etc), the low and high frequencies will be rolled off. There's not much you can do about it except to find a generic correction curve someplace and use that to compensate. But as a sound level meter reading absolute C- or A-weighted SPL's, it will be accurate.


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## Doctor X

Hi there,

Yes, that's me. I'm using this meter purely for setting levels, so you say that everything is accurate for that application and definitely more accurate than the standard meter? Correct me again, what does the "Verified" option do? I've clearly gone off the rails here as I must have assumed something else.


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## JohnM

Anechoic said:


> The CM-140 is a sound level meter that only has A- and C-weighted settings. Both of those weightings roll off the high and low frequencies, with the A-weighting setting producding sharper rolloff, but C-weighting is still down 14 dB at 10 Hz. The correction curves I ship with those meters (in theory) will correct for those extreme rolloffs and flatten the response. However boosting the levels that much (as much as 25 dB at 5 Hz) can create distortion problems similar to what you would get if you boosted the level of a graphic equalizer by 20 dB. That's the potential issue one might have to deal with.


There aren't any distortion problems if using a meter with software like REW, since the signal isn't actually being boosted in a hardware sense, the displayed level in measurement responses is simply scaled up to reverse the attenuation of the C weighting curve. The main problem is that signal and noise both get scaled up, so the measurement result at the very lowest frequencies has more noise than if measured with a mic. None of this is an issue if using a meter to measure SPL, however.


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## Doctor X

I just need reassurance that a) this verified meter is more accurate than the standard meter b) more accurate than the RS meter for measuring levels. That's it. 

For measuring REW I'll get a UMIK-1 at a later date.


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## Doctor X

No response?


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## Anechoic

Vaughan100 said:


> I just need reassurance that a) this verified meter is more accurate than the standard meter b) more accurate than the RS meter for measuring levels. That's it.
> 
> For measuring REW I'll get a UMIK-1 at a later date.


a) if by "standard meter" you mean "Galaxy CM-140 meter purchased at Amazon or someplace else, then the answer is "yes, the Verified meter is more accurate" by virtue of me putting an acoustical calibrator on it and setting the proper level. It's not going to be as accurate as a Bruel & Kjaer 2250, but then again is doesn't cost $8,000.

b) yes, it's more accurate than the Radio Shack meter for the same reason, plus the CM-140 has a smoother frequency response.


----------



## beezar

Ok, sorry if this is totally obvious to everyone, but I want to make sure. Tried doing a search but couldn't find the answer. I have a EMM-6 from CrossSpectrum and wanted to be sure exactly where I put the calibration file. So I put it under preferences -> Mic/Meter -> then browse to the calibration file, correct? and make sure the C-weighted box is not ticked? And do I use the narrow band 90 degree file?

Then do I do the same process of SPL calibration using the REW SPL meter button as described in the REW help files but with the microphone instead of an SPL meter? Anything else I need to do?

Thanks


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## JohnM

beezar said:


> I have a EMM-6 from CrossSpectrum and wanted to be sure exactly where I put the calibration file. So I put it under preferences -> Mic/Meter -> then browse to the calibration file, correct?


Correct.



> and make sure the C-weighted box is not ticked?


Correct


> And do I use the narrow band 90 degree file?


If you plan to point the mic straight up, yes.



> Then do I do the same process of SPL calibration using the REW SPL meter button as described in the REW help files but with the microphone instead of an SPL meter?


Yes.



> Anything else I need to do?


Nope.


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## aackthpt

A few questions for you Anechoic:

1. Can you calibrate a measurement mic that isn't one of the usual ones you sell or advertise calibration for if it appears to have the same or similar body?
2. Would putting it vs. an EMM-6 in your hearing aid chamber provide any useful information as to whether its self-noise is lower? The mic I'm looking at has a self-noise rated similarly to the LinearX microphone we discussed before but at a much lower cost, also it can use 48V rather than 9V phantom power.
3. I'm looking at measuring lateral fraction with ARTA, which requires a bidirectional mic. However I can't seem to find any bidirectional measurement mics easily. Any ideas, or suggestions where to go to find an answer?
4. Same question as 3 but with IACC and binaural in-ear mics (with myself as the dummy, given that I come a lot cheaper than the proper dummy heads). Any suggestions on what is a decent mic set for this purpose and what isn't?

Thanks,
John


----------



## Anechoic

aackthpt said:


> A few questions for you Anechoic:
> 
> 1. Can you calibrate a measurement mic that isn't one of the usual ones you sell or advertise calibration for if it appears to have the same or similar body?


Yes. I can and do measure mics of all kinds of shapes and types, including ribbons and large diameter condensers, as well as various mics with the ECM8000 body-type.



> 2. Would putting it vs. an EMM-6 in your hearing aid chamber provide any useful information as to whether its self-noise is lower? The mic I'm looking at has a self-noise rated similarly to the LinearX microphone we discussed before but at a much lower cost, also it can use 48V rather than 9V phantom power.


I can measure down to about 16-17 dBA, so as long as the mic noise floor is above that (typical EMM-6 noise floor is around 32 dBA), I can give you a number. For mics with a noise floor below 17 dBA, all I can report is a value of "<17 dBA."




> 3. I'm looking at measuring lateral fraction with ARTA, which requires a bidirectional mic. However I can't seem to find any bidirectional measurement mics easily. Any ideas, or suggestions where to go to find an answer?


"Bidirectional measurement mic"? Does such a thing exist? Usually when one is trying to make a directional sound measurement, you use a sound intensity probe, mic array, or two mics with a hard planar surface between them.



> 4. Same question as 3 but with IACC and binaural in-ear mics (with myself as the dummy, given that I come a lot cheaper than the proper dummy heads). Any suggestions on what is a decent mic set for this purpose and what isn't?


For this, I would just recommend using a pair of any reasonable omnidirectional microphones (this is a decent one, so long as you don't need data below ~ 50 Hz) and attach them to a pair of glasses near your ear, and use a cal file to correct any frequency response deficiencies of the mic (the Radio Shack mics are fairly flat up to about 10 kHz).


----------



## aackthpt

Anechoic said:


> "Bidirectional measurement mic"? Does such a thing exist? Usually when one is trying to make a directional sound measurement, you use a sound intensity probe, mic array, or two mics with a hard planar surface between them.
> 
> For this, I would just recommend using a pair of any reasonable omnidirectional microphones (this is a decent one, so long as you don't need data below ~ 50 Hz) and attach them to a pair of glasses near your ear, and use a cal file to correct any frequency response deficiencies of the mic (the Radio Shack mics are fairly flat up to about 10 kHz).


Thanks for the replies. I will contact you through the website if I get the mic.

A quote from the ARTA manual:


Code:


Early lateral energy is being measured with two close spaced microphones: omni-directional and 
bidirectional (with figure of eight directional pattern). Interaural cross correlation coefficients are 
measured with either a dummy head, or a real head, and with two small microphones placed at the 
entrance to the ear canals.

and later


Code:


To measure spatial parameters a sound system with two microphone input channels is required. For 
measurement of IACC two small identical microphones must be used at the entrance of the ear 
channel of a dummy or a real head. For measurement of lateral energy fraction, an omnidirectional 
microphone should be connected to left channel and bidirectional microphone to right channel. 
Microphones should be calibrated, at least average difference in sensitivity have to be known.

I'll investigate the devices you mentioned since I'm not familiar with them. Anyway I figured a bidirectional measurement mic didn't exist since I couldn't find anything specifically called that. However a mic array or two mics with a plate between can't be used since it is only one channel of acquisition (unless possibly it's two mics with a mixer I guess). Anyway for this one :dontknow:


----------



## JohnM

In that context "bidirectional" refers to the mic's polar pattern, see http://en.wikipedia.org/wiki/Microphone#Bi-directional


----------



## Anechoic

aackthpt;585217
I'll investigate the devices you mentioned since I'm not familiar with them. Anyway I figured a bidirectional measurement mic didn't exist since I couldn't find anything specifically called that. However a mic array or two mics with a plate between can't be used since it is only one channel of acquisition (unless possibly it's two mics with a mixer I guess). Anyway for this one :dontknow:[/QUOTE said:


> The book "Room Acoustics" uses almost the same wording as the ARTA doc. It's a weird thing to recommend, but I suppose that is the technique that's used. I'll post a message to the National Council of Acoustical Consulting forum and see what those folks have to say about the matter.
> 
> 
> 
> JohnM said:
> 
> 
> 
> In that context "bidirectional" refers to the mic's polar pattern, see http://en.wikipedia.org/wiki/Microphone#Bi-directional
> 
> 
> 
> Right, but so far as I know, no one makes a measurement microphone in anything other than an omnidirectional pattern. I've measured by share of figure-of-eight recording mics and have been hard-pressed to find ones that are flat outside of 200 Hz to 7-8 kHz (usually by design).
> 
> 
> edit: just found this link which discusses using a dummy-head measurement to determine the lateral fraction (end of sec 5.2.1)
Click to expand...


----------



## Jargon

Hi all.

I recently bought an Earthworks M30 in order to use it for acoustic measurements and subwoofer testing and maybe DIY projects in the future. 
I am using a Focusrite 2i2 as a mic pre amp that is flat to 10Hz from measurements I have found but will also be replaced later by an even more accurate preamp.


Now, I want to be able to measure absolute SPL levels for subwoofer max output testing and I was hoping to use the M30 in conjunction with REW or ARTA at very low frequencies down to 10Hz and later on, as subs are added, even lower. 

My questions are:


A) The Earthworks M30 came with a calibration file but only down to 770Hz. Contacting earthworks their engineer told me to get the calibration value form the 775Hz (not there) and copy it down to the desired frequency (10 or 5Hz) at appropriate intervals or leave it blank as the mic is accurate +-0.25d db down to 5Hz. 

Is there a point to send the mic for an extra calibration to cross spectrum labs? Would extra information such as polar response be of value? What a bout placement when measuring? (Vertical, facing)


B) Is REW appropriate for measuring max spl levels for subwoofer testing? Will providing it with a reference 75db point while calibrating its SPL be enough to then measure accurately the rest of the frequency band with the M30?


C) My SPL (US Blaster) crapped out so I bought one for my iphone 4 (studio six digital) for the moment. I was thinking of buying the Galaxy from Cross Spectrum Labs with verified + calibration. Will this be appropriate then as a ref point at 75db or any other software? Is there something better I could get from cross spectrum if needed?


Thank you in advance.


----------



## AudiocRaver

> A) The Earthworks M30 came with a calibration file but only down to 770Hz. Contacting earthworks their engineer told me to get the calibration value form the 775Hz (not there) and copy it down to the desired frequency (10 or 5Hz) at appropriate intervals or leave it blank as the mic is accurate +-0.25d db down to 5Hz.
> 
> Is there a point to send the mic for an extra calibration to cross spectrum labs? Would extra information such as polar response be of value? What a bout placement when measuring? (Vertical, facing)


The M30 spec page shows typical frequency response being flat to 10 Hz and down 3 dB at 5 Hz. Based on that, if you are looking for high accuracy at 5 Hz, having the microphone calibrated might be wise. Polar response is only an issue above 1 kHz or so with a good measurement omni, and there are guidelines in the REW help file and online help threads for mic placement and angle. For some measurements, off axis-angles are useful. For off axis accuracy at the higher frequencies, the additional info from an off-axis calibration would be needed.



> B) Is REW appropriate for measuring max spl levels for subwoofer testing? Will providing it with a reference 75db point while calibrating its SPL be enough to then measure accurately the rest of the frequency band with the M30?


Yes, and yes. Calibrating the soundcard frequency response will be necessary for the accuracy you want at those low frequencies. For measuring max SPL levels, recalibrating REW at a higher SPL might be needed.



> C) My SPL (US Blaster) crapped out so I bought one for my iphone 4 (studio six digital) for the moment. I was thinking of buying the Galaxy from Cross Spectrum Labs with verified + calibration. Will this be appropriate then as a ref point at 75db or any other software?


Yes. Absolute SPL accuracy is not super critical, you just need a repeatable calibration source in case the S EL calibration in REW gets lost and needs to be redone.


----------



## Jargon

So for the moment I can trust the M30 and since I need to invest in more subwoofers to get meaningful response even down to 10Hz (now playing with two dual 15" sealed cabinets) a further calibration can wait a bit in favor of other needs such as a new SPL.

The calibration of the soundcard is another whole issue since I am using an HDMI out for the output. Yet, I have an Assus Essence STX in the HTPC that I could calibrate and use as the output device for measurements but then I will have to use my Onkyo 5507 crossovers to get sound on the sub instead of Jriver's active ones. While playing back I send the output signal to the amps through the balanced outputs but to calibrate I will have to use the RCA outputs for the loopback cable to the input device (Focusrite in this case). Oh well I will check all possible routes to see if there are discrepancies.

Regarding the criticality of absolute SPL precision, it sure is not important for FR but to calibrate the REW SPL for accuracy in max output measurements isn't it so? 

However, how do I apply the correction curve to the Galaxy measurement of the signal REW outputs in order to calibrate its SPL? In other words I am trying to calibrate the REW SPL as close as possible to perfect. If of course it is possible. 

Another option would be the purchase of a calibrator device and calibrate the ARTA SPL which also requires other data (I/O voltages, probably a scope and a calibrator device as well). Yet, even more expenses since also ARTA is not free if you want to save data. 


Finally, does the calibrator device need calibration as well once in a while? Lol, what a calibration ordeal have I gotten into!


----------



## Anechoic

Jargon said:


> Hi all.
> 
> 
> 
> A) The Earthworks M30 came with a calibration file but only down to 770Hz. Contacting earthworks their engineer told me to get the calibration value form the 775Hz (not there) and copy it down to the desired frequency (10 or 5Hz) at appropriate intervals or leave it blank as the mic is accurate +-0.25d db down to 5Hz.
> 
> Is there a point to send the mic for an extra calibration to cross spectrum labs? Would extra information such as polar response be of value?


No. Those mics will be flat to well below 10 Hz. The Earthworks guys know what they're doing, 



> What a bout placement when measuring? (Vertical, facing)


For low frequency measurements, it won't matter, the Earthworks mics will be truly omnidirectional below 5 kHz.


----------



## AudiocRaver

If you are using HDMI output, ignore the comment about sound card calibration.

If you really need that kind of absolute accuracy in your SPL measurements, you need a reference SPL meter with guaranteed high absolute accuracy. For most in-home applications that extreme accuracy is simply not needed. If you are doing something commercial, then it might be called for. Of course, if it is important to YOU, then that is what matters. Once Room EQ Wizard is calibrated, working along with a properly calibrated mic, it can provide high accuracy regardless of level or frequency.

An accurate SPL meter, sent in for routine calibration, should satisfy your accuracy needs. When you start buying calibrators, then those have to be calibrated, too. If you are really concerned about calibration drift, I would buy a second SPL meter for crosschecking, then you always have a backup if one gets dropped or broken or is sent in for calibration. When selecting SPL meters, be sure to watch for guaranteed accuracy specs, including drift numbers for temperature.


----------



## Jargon

First of all thank you for the clarifications. 

The question then comes down to whether the Galaxy CM-140 Verified+ provides that accuracy needed for calibrating REW, serving as a reference point. 

*So is there a way to apply the correction curve of the Verified + Galaxy to the test tone output by REW during its SPL calibratrion. *


It is cheaper for me based in Europe (probably) to buy a Galaxy from Cross Spectrum. Then after a period of time to buy a second one and then sell the first to someone not caring that much and keep on this cycle (replacing one of the two every six months).



P.S. The HDMI output will be replaced in the future with another digital interface (AES/EBU) on a Lynx AES to a Metric Halo ULN-8.


----------



## Anechoic

Jargon said:


> It is cheaper for me based in Europe (probably) to buy a Galaxy from Cross Spectrum. Then after a period of time to buy a second one and then sell the first to someone not caring that much and keep on this cycle (replacing one of the two every six months).


If you're concerned about SPL calibration, it's probably cheaper to just buy a Type 2/Class 2 calibrator for a couple of hundred Euros. As long as you don't drop it or otherwise abuse it, it likely won't drift more than a few tenths of a dB over a couple of years.


----------



## AudiocRaver

Jargon said:


> The question then comes down to whether the Galaxy CM-140 Verified+ provides that accuracy needed for calibrating REW, serving as a reference point.
> 
> *So is there a way to apply the correction curve of the Verified + Galaxy to the test tone output by REW during its SPL calibratrion. *


No, and it is not necessary, nor would it be very useful.

The SPL meter is used to calibrate Room EQ Wizard with pink noise running and the calibration mic as input. Then the calibration mic's correction curve provides measurement accuracy over the entire frequency range. There is no way to put the SPL meter correction curve into REW. You could probably manually fake it into the soundcard calibration file slot, but then you would have to remember to only activated when you were doing a cross check to verify your SPL measurement accuracy at different frequencies. That is a lot of work for very little benefit. Trust REW to do that work for you. It will.

The SPL meter is calibrated to be accurate at 1 kHz reference frequency. SPL meters use RMS sensing measurement algorithms, so an 85 dB SPL sine wave and an 85 dB SPL band of pink noise centered at 1 kHz will give the same result. Calibrate using REW using the speaker cal pink noise setting, and you will have an extremely accurate calibration. Use pink noise when calibrating, not a sine wave, because with a sine wave, even a small separation between the SPL meter and the calibration mic positions can result in error. Use the speaker cal setting because it gives you a band of pink noise between 500 Hz and 2 kHz, where the SPL meter is most accurate. From that point forward, your measurements will be most accurate using REW and your earthworks mic, because the earthworks mic is far more accurate at the low frequencies, the SPL meter will have a large correction factor there. That is the way I would do it.



Jargon said:


> It is cheaper for me based in Europe (probably) to buy a Galaxy from Cross Spectrum. Then after a period of time to buy a second one and then sell the first to someone not caring that much and keep on this cycle (replacing one of the two every six months).


That's a lot of SPL meters. It is your business, but I am having just a teeny tiny problem understanding why that level of absolute SPL accuracy is necessary, all due respect. Enough said. It is your business, and you may have a very good reason for it.



> If you're concerned about SPL calibration, it's probably cheaper to just buy a Type 2/Class 2 calibrator for a couple of hundred Euros. As long as you don't drop it or otherwise abuse it, it likely won't drift more than a few tenths of a dB over a couple of years.


I agree, rather than buying several SPL meters per year, this is probably a better long-term choice.

I truly wish you the very best. Perhaps I went into unnecessary detail, I was just trying to anticipate further questions and get them answered in one shot. Hopefully our responses have been helpful to you, that is our intention.:sn:


----------



## Jargon

Thanks a lot for the wise advice. It certainly makes things clear now so I will do as you suggest. 

I will buy a calibrator since I know now it does not drift as much as I thought over time and it will be stored under ideal conditions in a dry and "dark" spot with stable temperature. 

With that calibrator I might be able to recalibrate my existing SPL meter since it has a calibration pot on it but the company which made it never replied to mails regarding its calibration procedure and I had no idea back then that devices such as a this existed. 

With regards to accuracy, I do not expect 100% absolute values since that is truly hard. However, I want to stay as close as possible when measuring max SPL values of output especially in the very low frequencies where it is hard to achieve meaningful output and a 3db difference can be missing the target or not. Not the end of the world but it could mean an extra subwoofer before you hit reference SPL or not considering diminishing returns as well. 

Yet, I will have to deal with fine tuning where placement options or specific EQ filters (e.g. LT in sealed cabinets) combined produce increased output down very low but a decrease past a higher point or vice versa. Having the best possible reference point (i.e. +/- 1.5db) when measuring makes things easier while exploring the effects of various factors given specific limitations and/or narrow margins some times and might be a hit or miss case of a detail that a wide measurement variation could otherwise hide. 


You are certainly helping a lot here though! Thanks again. 



P.S. Any specific calibrator you could suggest and which type? (94 - 114db?)


----------



## Anechoic

Jargon said:


> P.S. Any specific calibrator you could suggest and which type? (94 - 114db?)


At the Type 2/Class 2 price points, there's not going to be a lot of difference from unit to unit. In terms of 94/114, if you have to choose, I typically recommend choosing a level closest to the level you usually measure at. So if you make measurements at 80 dB, get a 94 dB calibrator (or use the 94 dB setting on calibrators with switchable levels), if you measure at 120 dB, get the 114 dB calibrator. All of my calibrators (2 GenRad 1986's, 4 Larson-Davis CAL200's) are switchable, but I use 94 dB pretty much exclusively.


----------



## Jargon

I've seen some switchable ones so I will pick one of those.


----------



## Jargon

Well after some research the choice for an acoustic calibrator comes down to these 3 models:

This one at 199 Euros (94-11-db)

http://www.content.ibf-acoustic.com/catalog/product_info.php?cPath=31_36&products_id=42

This one at 330 Euros +40 shipping (94db only)

http://www.cirrusresearch.co.uk/acoustic_calibrators/


And this one at 288 Euros (94-114 db) 

http://www.thomann.de/gb/galaxy_audio_cm_c200.htm


The Galaxy has some issues with the Earthworks M30 with the adapter that does not fir tight so a custom might be needed.

The Cirus is the most expensive but it is a reliable company and does not have a 114db setting.

The iSEM one is the cheaper and they can send it with a custom adapter (23 Euros) for a perfect fit of the Earthworks M30/.

So it seems I should go for the iSEM one.

What about their reliability and accuracy? Does anyone know about those three and how accurate they are?


----------



## Anechoic

Jargon said:


> What about their reliability and accuracy? Does anyone know about those three and how accurate they are?


With respect to reputation I would probably rank them 1) Cirrus; 2) Galaxy, and 3) iSEM, but I suspect any of the three will be adequate.


----------



## Jargon

I thought so. The iSEM is officially being carried by on the online store of the SMAART developers making me think they have at least tested it as well as their microphones that they also sell. 

The thing with the Galaxy is reports from other users of the Earthworks M30 not fitting 100% (loose) but that was a post back from 2008. My M30 came with a 1/2" adapter so maybe it is perfectly fine.

In the end I will flip coins I think! Lol. Nonetheless, for what I want it as long as the iSEM is not totally out of specs and instead of +-0.5db variance it has +-3db then it seems to be the best deal out of the three price wise.


----------



## Phillips

Herb does the UMM-6 USB mic have the sensitivity factor available?


----------



## Anechoic

Phillips said:


> Herb does the UMM-6 USB mic have the sensitivity factor available?


No, the factory Dayton file doesn't give a sensitivity value and I don't trust measuring it simply because I don't know what settings constitute zero gain.


----------



## JohnM

Anechoic said:


> No, the factory Dayton file doesn't give a sensitivity value


I think it is in the first line of the Dayton cal files, e.g.

"Sens Factor =-23.555dB, SERNO: 1280303"



> and I don't trust measuring it simply because I don't know what settings constitute zero gain.


For these USB mics it is typically the rms value of the data from the mic in dB FS when driven by a 94 dB SPL calibrator with the Windows volume control set to 1.0, but there can be some ambiguity as to whether the rms level of a full scale sine wave is treated as -3 dB FS or 0 dB FS, and the effect of a 1.0 volume setting can be different between Windows XP (which I think the factory uses) and Windows 8. One option could be to simply copy the Dayton line across as supplied so that the files retain the same info.


----------



## Anechoic

JohnM said:


> I think it is in the first line of the Dayton cal files, e.g.
> 
> "Sens Factor =-23.555dB, SERNO: 1280303"


You are correct, I forgot that I deleted that line from the test files I downloaded because it screwed up my import script.



> For these USB mics it is typically the rms value of the data from the mic in dB FS when driven by a 94 dB SPL calibrator with the Windows volume control set to 1.0, but there can be some ambiguity as to whether the rms level of a full scale sine wave is treated as -3 dB FS or 0 dB FS, and the effect of a 1.0 volume setting can be different between Windows XP (which I think the factory uses) and Windows 8.


That ambiguity is exactly what prevents me from offering sensitivity measurements for USB mics. There are ways to confirm it, say by sticking the USB mic in the same field as one of my reference mics + meters and seeing if plugging in the factory (or other) sensitivity numbers into ARTA/etc give the same SPL results, but that's enough of a pain to not be worth the effort for me.



> One option could be to simply copy the Dayton line across as supplied so that the files retain the same info.


Yeah, but the implication would be that I endorse those factory sensitivity number, which I don't. Not to say they're wrong (all indications are that they're at least pretty close), but if my name is on it, I want to be able to measure it directly.


----------



## Phillips

For Cross - Spectrum Calibrated Dayton EMM-6 and Behringer ECM8000 microphones with: 

0 degrees calibration files
45 degrees calibration files
90 degrees calibration files

Can you describe the senarios (when they should be used) for each of these calibration files? 

Which mic orientation should/ideal be used for each senario/file?

Thanks in advance


----------



## Anechoic

Phillips said:


> For Cross - Spectrum Calibrated Dayton EMM-6 and Behringer ECM8000 microphones with:
> 
> 0 degrees calibration files


Loudspeaker measurements, microphone pointed directly at speaker.



> 90 degrees calibration files


Room acoustics/calibration measurements, microphone pointed straight up at ceiling or tilted slightly toward front speakers.



> 45 degrees calibration files


For experimentation purposes.


----------



## AudiocRaver

Phillips said:


> For Cross - Spectrum Calibrated Dayton EMM-6 and Behringer ECM8000 microphones with:
> 
> 0 degrees calibration files
> 45 degrees calibration files
> 90 degrees calibration files
> 
> Can you describe the senarios (when they should be used) for each of these calibration files?
> 
> Which mic orientation should/ideal be used for each senario/file?
> 
> Thanks in advance


My suggestion: For room measurements, pick one and use it for all measurements. Otherwise it becomes difficult to compare measurements taken at different times, under different conditions. For close speaker measurements, always use 0 degrees.


----------



## Anechoic

Effectively immediately, we're no longer selling calibrated ECM8000 mics. We will continue to offer Dayton EMM-6/UMM-6 mics and Galaxy CM-140 sound meters (and very soon, UMIK-1 mics).

To make a long story short: ECM8000 quality has declined to a point where they are utter and I'm sick of messing with them.


----------



## monomer

Question: When will you be shipping UMM-6s again? The day when I ordered mine there was a message at the bottom of the page saying they would be shipping the week of May 6... so today I visit the page and see the message has now changed to read they will be shipping in 7 to 10 days... problem is I don't know how long that message has been up there. Are those only 'working' days or they 'regular' days of the week? Will I get an email when it ships? Thanks.


----------



## Anechoic

Mics are shipping on a first-come/first-served basis, orders made from April 26 through yesterday should ship by the end of the week, new orders should ship by early next week, and (hopefully) orders made next week should be shipping in a few days. The 7-10 days are "normal" days, not working days (in other words, 1 to 1.5 weeks, not 1.5 to 2 weeks). You should get a shipping notification from USPS when the order ships.

Did you put your HTS username in the "Instructions to merchant" field when you made your order? I don't see "monomer" in any of the UMM-6 orders. 

(If your initials are "ML", "CG" or "EI", your UMM-6 is shipping tomorrow)


----------



## monomer

No I didn't know I could do that? Was there some sort of discount for doing it?
Anyway, my initials are GC... that's with first name (Greg) followed by last name... in Michigan. I placed the order with CSL on April 26.


----------



## Anechoic

Sorry, I meant "GC" (hey it is 1am!). Your order is shipping tomorrow. 

You are entitled to a HTS discount, I'll take care of that right now.

I was traveling for business all of last week which is why there was a delay in filling orders. I got back midnight Sun/Mon, processed a dozen orders and those will ship on Tuesday (including yours).


----------



## monomer

Yeah!!! on all accounts. I'm getting kinda excited now... I wasn't expecting it until next week sometime but its now looking like I might have it to play with this weekend. Great!!! Thanks...


----------



## Kisakuku

Anechoic said:


> Effectively immediately, we're no longer selling calibrated ECM8000 mics. We will continue to offer Dayton EMM-6/UMM-6 mics and Galaxy CM-140 sound meters (and very soon, UMIK-1 mics).
> 
> To make a long story short: ECM8000 quality has declined to a point where they are utter and I'm sick of messing with them.


So what's the verdict on UMM-6 vs EMM-6 for REW if price of USB soundcard / mic preamp is not an issue? I remember the graph you posted with a much higher noise floor for the USB mics, yet they seem to be very popular. Is it just the overall ease of setup / price issue, flexibility of using HDMI for test tones or something else?


----------



## Anechoic

If money isn't an issue, I'd recommend going with a soundcard + EMM-6 over the UMM-6.


----------



## Kisakuku

Anechoic said:


> If money isn't an issue, I'd recommend going with a soundcard + EMM-6 over the UMM-6.


That was my thinking as well when I bought a US122MKII and an EMM-6 calibrated by you. Thanks for the confirmation.


----------



## AudiocRaver

RE posts 261 through 265: Now _that_ is great customer service...

========



Anechoic said:


> Effectively immediately, we're no longer selling calibrated ECM8000 mics. We will continue to offer Dayton EMM-6/UMM-6 mics and Galaxy CM-140 sound meters (and very soon, UMIK-1 mics).
> 
> To make a long story short: ECM8000 quality has declined to a point where they are utter and I'm sick of messing with them.


Sorry to hear that. In a discussion with Behringer reps at a Guitar Center demo awhile back, they talked about their manufacturing model as it relates to quality. They said that Behringer has their own manufacturing plant in China so they get the benefit of low labor and materials costs, but can control the quality themselves. Sounds good in theory anyway.

Out of curiosity, what kinds of quality issues have you run across, and over what time period have you seen the decline?


----------



## Anechoic

AudiocRaver said:


> Out of curiosity, what kinds of quality issues have you run across, and over what time period have you seen the decline?


There are two types of quality issues that have started to become a real problem:

1. Outright failure of the microphone characterized by a 60-Hz (and its harmonics) hum that make low-frequency measurements impossible (sometimes this shows up as a buzz or fluctuating low-frequency response). On a good week, about 10% of mics have this, on a bad week, maybe 30%.

2. Severely diminished low-frequency response, characterized by extreme low-frequency rolloffs of around -30 to -35 dB at 5 Hz (compared to a more typical value of -10 to -15 dB) and around -5 to -8 dB at 20 Hz (compared to a more typical value of 0 to -3 dB). These mics are technically good-to-go, but the freq response is so messed up I can't in good conscience charge full price for these, so I let them go at a discount. These were rare, but now I'm seeing about 25% of mics hit this mark.

In the last three weeks of measuring ECM8000, about 60% of mics fell into one of these two categories. After the mics I looked at on Monday, I decided I was done. I'll reevaluate in a few months, but for now, I'm moving on.

To be fair, the quality of Dayton EMM-6 mics has also fallen, but not nearly as much as the Behringer mic. The quality of the EMM-6 also started at a higher point.


----------



## Phillips

Anechoic said:


> To be fair, the quality of Dayton EMM-6 mics has also fallen, but not nearly as much as the Behringer mic. The quality of the EMM-6 also started at a higher point.


When did these start to fall off?

Where are the problems with these, the same as Behringer?


----------



## Anechoic

There's an earlier thread called something like "state of microphones" (I'm too lazy to look it up right now) where I talk about it. There have been little dips in quality after the EMM-6 was first introduced (I saw zero bad ones in my first couple of hundred, that increased to maybe 1-2 out of every hundred for the next few batches), but in the last year to 18 months it's increased enough to make me pay attention (maybe 5-10 out of every hundred) but still nowhere near as bad as ECM8000's are now.

The problems are basically hum/buzzing, or mysteriously going DOA after a few days of use. I haven't seen the severe LF rolloff that I've observed with the ECM8000.


----------



## Phillips

Anechoic said:


> The problems are basically hum/buzzing, or mysteriously going DOA after a few days of use.


The thread was started by you?

You check for these before release?

Have these mics ever been returned back to you because of these issues?


----------



## Anechoic

Phillips said:


> The thread was started by you?


This is the thread.



> You check for these before release?


Buzzing/hums show up in the data when the mics are calibrated, I don't specifically check for them. Mics going dead usually happens after customers have received them.



> Have these mics ever been returned back to you because of these issues?


Yep.


----------



## Phillips

Anechoic said:


> This is the thread.
> 
> 
> 
> Buzzing/hums show up in the data when the mics are calibrated, I don't specifically check for them. Mics going dead usually happens after customers have received them.
> 
> 
> 
> Yep.


Thanks for the thread link, had a read. Looked for it briefly last night but couldn't find it. Probably on next page  

Many come back in the last 9-10 months?


----------



## Anechoic

Phillips said:


> Thanks for the thread link, had a read. Looked for it briefly last night but couldn't find it. Probably on next page
> 
> Many come back in the last 9-10 months?


Around 5 or so.


----------



## Phillips

Which is the best mic overall between the UMM-6 and UMIK or other USB mic?


----------



## Anechoic

Phillips said:


> Which is the best mic overall between the UMM-6 and UMIK or other USB mic?


I would give the nod to the UMIK-1 over the UMM-6 for two reasons: 1) slightly better low frequency response, and 2) not as fragile (I'm seeing a lot of complaints about UMM-6's either arriving with the barrel broken off, or the barrel breaking off at the slightest bit of stress, such as being dropped on a carpet).

Is there another USB mic out there (other than the OmniMic)?


----------



## Phillips

Anechoic said:


> I would give the nod to the UMIK-1 over the UMM-6 for two reasons: 1) slightly better low frequency response, and 2) not as fragile (I'm seeing a lot of complaints about UMM-6's either arriving with the barrel broken off, or the barrel breaking off at the slightest bit of stress, such as being dropped on a carpet).
> 
> Is there another USB mic out there (other than the OmniMic)?



True the Omnimic, have you had any dealings with them?



Calibrated Mic (XLR) by you and Pre / Soundcard vs USB mic

Which is the best out of the two, other than USB being convenient?


----------



## Kisakuku

Phillips said:


> Calibrated Mic (XLR) by you and Pre / Soundcard vs USB mic
> 
> Which is the best out of the two, other than USB being convenient?


See couple pages back:



Anechoic said:


> If money isn't an issue, I'd recommend going with a soundcard + EMM-6 over the UMM-6.


----------



## Anechoic

Phillips said:


> True the Omnimic, have you had any dealings with them?


I've measured one, the freq response was far worse than the UMM-6.


----------



## Phillips

Anechoic said:


> If money isn't an issue, I'd recommend going with a soundcard + EMM-6 over the UMM-6.


You have compared the EMM-6 + soundcard with the UMM-6.

Would this also apply to the other USB mics (UMIK and Omnimic)?


----------



## Phillips

Kisakuku said:


> See couple pages back:


Thank you


----------



## Anechoic

Phillips said:


> You have compared the EMM-6 + soundcard with the UMM-6.
> 
> Would this also apply to the other USB mics (UMIK and Omnimic)?


Yes.


----------



## monomer

Anechoic said:


> I would give the nod to the UMIK-1 over the UMM-6 for two reasons: 1) slightly better low frequency response, and 2) not as fragile (I'm seeing a lot of complaints about UMM-6's either arriving with the barrel broken off, or the barrel breaking off at the slightest bit of stress, such as being dropped on a carpet)...


I own an EMM-6 and its shell is quite stout very similar to the UMIK in build... in fact, I'd be willing to bet they are both made in the same manufacturing facility. I also have owned the UMIK (Rev B) but returned it for refund due to the ever changing calibration issues they were having at the time. I now own a UMM-6 and actually am quite pleased with it. I can see where, if dropped, the UMM-6 would be more fragile than a UMIK, or even the EMM-6 for that matter, simply because the narrow end that holds the capsule is much smaller in diameter... all else being equal, a thinner stem is just going to be weaker. As for the better low frequency response... this is not so much an issue as the calibration file that comes with it and if purchasing a UMIK direct from MiniDSP I personally wouldn't trust it's calibration file but from CSL (Anechoic) that's a different story. There is a third thing that wasn't mentioned above so I guess I will: The thing I've also noticed is the inherent noise. My EMM-6 has a very low noise floor that's also free from spurious 1kHz spikes. By contrast, the UMIK I had, had an issue with a high noise floor but also it had a curious 1kHz spike (that persisted at all freqs above it in 1kHz intervals). It wasn't really a problem for me because I take all my measurements near reference but for other UMIK owners it apparently was a significant issue... eventually MiniDSP did respond with a mod (Rev C) to the board to remove the spikes and overall it apparently has accordingly also lowered the noise floor. Well, my UMM-6 has this same high noise floor and 1kHz spike pattern that the UMIK exhibited before the revised board. Again, it poses no problems for me but I wonder if it might not be an issue for others?

Anechoic... your reasons for picking the UMIK over the UMM-6 I don't think is any big deal at all, especially since you are providing purchasers such an accurate calibration file for both, however I think the noise issue (with those 1kHz spikes) may be a far more significant factor as to why the UMIK would be a better choice over the UMM-6. If I had known you were going to be also selling the UMIK at the time I placed my order for the UMM-6, I would have probably chosen the UMIK. Since the UMIK I had was a Rev B and exhibited those noise issues, could you verify to others here that indeed those noise issues have been dealt with and solved on the newer UMIKs (Rev C)?

Bottom line... I'm very pleased with my UMM-6 with CSL calibration file but I believe others should be aware of the noise issue with it when trying to decide which to purchase between the UMIK and the UMM-6.


----------



## Anechoic

monomer said:


> My EMM-6 has a very low noise floor that's also free from spurious 1kHz spikes. By contrast, the UMIK I had, had an issue with a high noise floor but also it had a curious 1kHz spike (that persisted at all freqs above it in 1kHz intervals). [..] Well, my UMM-6 has this same high noise floor and 1kHz spike pattern that the UMIK exhibited before the revised the board.


Yep.



> Since the UMIK I had was a Rev B and exhibited those noise issues, could you verify to others here that indeed those noise issues have been dealt with and solved on the newer UMIKs (Rev C)?


I was told that this was addressed, but I haven't had a chance to verify that yet. It's on the list.


----------



## danny01

I was able to get an order in on the umik. I notice that the site has been updated with a later shipping date. Is this date for a later batch? Will the earlier orders start shipping out at this date or 6/3?


----------



## Anechoic

danny01 said:


> I was able to get an order in on the umik. I notice that the site has been updated with a later shipping date. Is this date for a later batch? Will the earlier orders start shipping out at this date or 6/3?


Assuming your initials are "DH" your order will ship tomorrow. Also you should PM or email me to claim your HTS discount.


----------



## danny01

Sent email


----------



## Dwight Angus

Anechoic
Can you tell me when you will restock the UMIK-1? I tried to order it and you website indicated it is sold out.
Cheers


----------



## Anechoic

Dwight Angus said:


> Anechoic
> Can you tell me when you will restock the UMIK-1? I tried to order it and you website indicated it is sold out.
> Cheers


It might be a while unfortunately, my schedule is insane right now (and flight cancellations aren't helping... greetings from Atlanta!). At least a couple of weeks.


----------



## mc_lover

I cannot find ECM8000 microphone calibrated on the web store any more.
is it discontinued?


----------



## Anechoic

mc_lover said:


> I cannot find ECM8000 microphone calibrated on the web store any more.
> is it discontinued?


CSL is no longer selling ECM8000 microphones.


----------



## wsxcde

Any update on when the MiniDSP UMIK-1 will be available for ordering?


----------



## Dwight Angus

I ordered the UMIK-1 can you tell me the approximate shipping date?


----------



## Dwight Angus

Regarding my CSL UMIK-1 order . I received the USPS shipping notice today so its on its way.


----------



## wsxcde

wsxcde said:


> Any update on when the MiniDSP UMIK-1 will be available for ordering?


I was able to pre-order the UMIK-1 in the Cross Spectrum web site just now. :clap:


----------



## onyx00

Just placed an order for the UMIK-1 yesterday - hoping they have them back in stock and I won't end up waiting too long. I'm running out of time until I start a new job and won't have time to "play" with this stuff anymore


----------



## e-t172

Phillips suggested I post this here, so here I go:

The following message was originally posted on the MiniDSP forums, but unfortunately I received no response in 4 days, so I'm posting it here hoping that someone can help me:

I'm definitely interested in buying one of those UMIK-1 microphones, but I've read a lot of concerns about their elevated noise floor (~50dB dBA, whereas other microphones in the same price range can do ~30dBA). To be fair this matches the specifications, which indicate max SPL at 133dB SPL and a noise floor at -74dBFS, which translates to an absolute noise floor of 59dB SPL. Nevertheless, I would appreciate being able to use the UMIK-1 to do THD measurements which require a clean, low noise floor. 

I have the following questions:

Last time I checked, there was an issue with the noise floor being dominated by a nasty spike at 1kHz followed by its harmonics. Apparently this was an issue with an early batch and should be fixed now. Could someone confirm this?
What are the numbers regarding the noise floor for the recent revisions of the UMIK-1? I would greatly appreciate if people who ordered one recently could post a screenshot of what an RTA looks like in a very quiet room.
Is the UMIK-1 well-isolated with regard to USB power noise or should I be careful what I plug this thing into?
Does increasing the recording volume (i.e. in Windows) have any effect on the *absolute* (i.e. in dB SPL) noise floor? At first glance I would guess that the volume control is digital so it wouldn't have any effect, but I would sure like a confirmation.
It appears that you can open the UMIK-1 and change the sensitivity using DIP switches. Depending on where the noise is coming from, increasing the sensitivity might, in theory, lower the absolute noise floor in the same proportion. I don't require low sensitivity (I would be fine with just 110dB max SPL), so that wouldn't be a problem.
Has anyone tried this? Does this tweak have any effect on the *absolute* (i.e. in dB SPL) noise floor?
Is it safe to do this with regard to altering the microphone - i.e. is there a risk of causing damage, screwing up the calibration, etc.?


Thanks in advance for your answers!


----------



## |Tch0rT|

I got my calibrated UMM-6 from CSL earlier this week. Thanks Anechoic!


----------



## Doctor X

Anechoic, I've sent you 2 PM's. Please respond.


----------



## Anechoic

My apologies, but I just started a three-week period of travel and I don't have a lot of free time. 

Reagarding confirmation of fized issues with the UMIK-1, what specific issues are you referring to? For the UMIK-1 we only offer Basic+ calibration level. Regaring noise floor, the older UMIK-1s have a noise floor of around 50 dB meaning that you're measurement needs to be at least 10 dB higher to give meaningful results (probably 20-30 dB higher for waterfall measurements). THe newer UMIK-1's supposedly have a lower noise floor but I haven't had a chance to test that out.

You should be able to find shipping prices on my site.


----------



## Doctor X

Hi,

Well I read about issues with the accuracy of the mics. It used to be a problem apparently. So you're saying that's not an issue anymore. 

I'll take a look at the website for shipping. Thanks.


----------



## Doctor X

There is no mention of shipping prices on your site, at least that I could see. All I get is a $95 including shipping with the UMIK-1, but I assume that isn't to South Africa.


----------



## e-t172

Doctor X said:


> Well I read about issues with the accuracy of the mics. It used to be a problem apparently. So you're saying that's not an issue anymore.


Define "accuracy". Even with an elevated noise floor these mics are quite accurate for measuring frequency response. It is only an issue when doing other kinds of measurements like THD.


----------



## Doctor X

There were bad batches. I remember there was a thread about it. It was a problem, but this was several months ago.


----------



## HifiZine

Doctor X said:


> There is no mention of shipping prices on your site, at least that I could see. All I get is a $95 including shipping with the UMIK-1, but I assume that isn't to South Africa.


It's linked from the "Pricing" tab. The link goes to:

http://www.cross-spectrum.com/measurement/international-shipping.html

You can also get it from the shopping cart, by clicking on "change" in the "shipping and handling" area.


----------



## Doctor X

Not sure how I missed it. Feel a little embarrassed now.  Thanks for pointing it out for me.


----------



## e-t172

FYI: someone on the MiniDSP forum measured the noise floor of the UMIK-1 and found good results (29.1 dB(A), 43.1dB(unwheighted)). I guess that makes the warning on the Cross-Spectrum labs website about noise floor obsolete.


----------



## SRW1000

The webpage for the UMIK shows that they're available and will ship next week, but when I try to check out, it's telling me that they're sold out. 

I tried clearing my cache, and using a different browser, but I still get the out of stock message.


----------



## sbdman

Ordered a UMIK-1 last Tuesday, when the site said they would start shipping today, but received it today, much faster delivery than I expected, and received in perfect shape.
Appreciate the thumb drive with correction factors, nice touch. Also contacted Anechoic, and he responded within minutes to my pm, and made me a very satisfied customer.

I did a quick comparison between miniDSP's correction factors, and the ones from CSM, I would have been about 2dB hot at 20Hz, and 6dB hot at 10Hz if bought from the factory. It's something I would never have heard, but the peace of mind of this professional service is exactly what I wanted.

Looking forward to running RTA through REW with a generated pink noise file tomorrow (thanks Mojave/desertdome). And thanks for helping at HTS.


----------



## SRW1000

Their website has been updated to say they have limited quantities in stock, and they will ship in the next five days. I was able to get the order to go through tonight. I can't wait to start using it.

Scott


----------



## mlange

UMIK-1 ordered this evening...... Looking forward to REW and this simplified hardware combination.

I've got an older B&K 2203, but the most recent calibration was from the early '90s.

Monitor config in my studio is the goal.

Cheers all and thanks for the great info!


----------



## e-t172

Hey,

So I got a question regarding the calibration files produced by Cross-Spectrum labs. Attached is a graph showing the 1kHz-20kHz portion of two calibration files, one for an ECM-8000 that I ordered years ago, and another one for a UMIK-1 that I just received.

There is one thing that worries me about how these frequency response graphs look: the sharp "edges" ("jumps") that they contain, especially visible between 3kHz and 5kHz. This looks very unnatural: sharp "jumps", which in the case of the ECM-8000 are followed by even more unnatural ruler flat "plateaus". The reason why I say they look unnatural is because their sharpness imply that they can only be the result of very high-order filters, and I'm not sure what would explain such peculiarities in these microphones.

Ideally, I would have expected a much smoother frequency response without any kind of sudden changes.

For what it's worth, the calibration file provided by MiniDSP for the UMIK-1 does not contain such oddities.

So my question is: are these sharp edges in the frequency response real or simply errors from the microphone measurements? And if they're real, what is the physical/electrical explanation for their presence?


----------



## sos_nz

SRW1000 said:


> Their website has been updated to say they have limited quantities in stock, and they will ship in the next five days. I was able to get the order to go through tonight. I can't wait to start using it.
> 
> Scott


Although it still says they have a limited number of UMIK-1's in stock, it's not going through the payment step as "your item(s) sold out".

Here's hoping the wait for these beauties isn't going to be too long.


----------



## Anechoic

e-t172 said:


> So my question is: are these sharp edges in the frequency response real or simply errors from the microphone measurements? And if they're real, what is the physical/electrical explanation for their presence?


It's an artifact from the smoothing process I use to remove room effects. It creates an error somewhere on the order of +/1 0.5 dB. I may have been a little too aggressive in the case of your mic. What is the serial number of that mic?


----------



## Anechoic

Hi all,

It may have seemed to some that I have dropped off the face of the earth in recent months, so I wanted to give an update about what's been going, touching on UMIK-1 availablity and shipping issues in particular.

The consulting part of our business has really taken off starting in the late spring and I spent a large part of the summer on the road so that really disrupted things on my end. Earlier this year I hired an assistant to help with mic calibrations, and he has helped to shoulder some of the load. We ran into some problems with his measurement setup during the summer so that delayed things. We have since resolved those problems, but he then had a family emergency, and since my schedule is still crazy we still had delays. We are getting back to normal, although I will warn that there will probably be delays again in late October/early November due to a pending move.

With regard to UMIK-1 availably, especially in contracts with the availability of the other products we sell: the Dayton EMM-6 & UMM-6 mics and Galaxy CM-140 meters come from local sources, so even if we sell out, we can usually get restocked in a couple of days. UMIK-1 are coming straight from Asia, so delivery takes on the order of a couple of weeks. I do order stock in relatively large batches, but I use the inventory control feature of PayPal to only sell small batches at a time so I can smooth out sales over a longer time frame. Otherwise, what would happen is that mics would sell out in a couple of days and then folks would have to wait weeks to get more mics. Even with this process, we're still selling mics at a very rapid pace, but MiniDSP is also selling mics fast so there are times when I may have to wait a couple of weeks for MiniDSP to re-up on their end. We're still navigating our way through this - and to their credit, MiniDSP has been very generous at help us work through this. I think we're both very (and pleasantly!) surprised at how well these mics are selling.

I've written before about the fragility of the Dayton UMM-6 USB mic. I spoke with someone at Dayton during the late spring about the issue and he mentioned that DA was aware of the issue and trying to work on it. That was right before the big gap in UMM-6 availability during the summer, so I can only hope they changed the manufacturing process to make the mics more durable. On my end, I haven't seen any come apart. If you've purchased a UMM-6 (from me or PE) after August and had one break, I'd like to hear from you. If these mics are shown to be more durable, I'll open them up again for international sales. One definite improvement I've seen in the UMM-6 is that they're much flatter on the high frequency range compared to the UMIK-1 and older UMM-6 mics. But until I'm sure the fragility problems have been addressed, I'll continue to recommend the UMIK-1 over the UMM-6 for USB mics.

The final issue I want to address are the various problems I've been having with the US postal service. For the first three or four years of shipping mics, I maybe had a shipping problem (packaging being lost or significantly delayed) two or three times per year, with most problems happening during the Christmas season when the USPS is handling a huge volume of packages. In the past 8 months we've had several dozen packages being waylaid or gone missing (most eventually found their way to the correct destination after several months, but at that point I had already sent replacement items). Speaking with my local USPS contacts it appears that due to budget cuts, the USPS closed our local (Springfield MA) distribution center and sent all distribution operations to Hartford CT and that caused a noticeable drop in service reliability. Furthermore it seems that some of the international shipping issues are being caused by similar cutbacks in foreign postal services.

I'm not quite sure how to address these postal issues. USPS is by far the most inexpensive option (and I basically charge the actual cost for shipping, there's no profit there), but quality has gone downhill. There's always the option of using FedEx and/or UPS - the advantage is that their delivery times are guaranteed. The downside is that I would have to raise shipping costs by around $5-$10 (depending on the destination) for domestic shipping, and up to ~$25 for international shipping. The price increase is due to the increased cost of the service itself, the fact that I would have to buy boxes (USPS provides shipping boxes for free) and I would have to pay for UPS/FedEx pickups (or drive way out of my way to drop them off at authorized shipping centers). While I do ship a lot of packages (we do something like 15% of the volume at the local post office) we don't ship any near enough to be eligible for volume pricing unfortunately. I'd love to hear from folks about whether they would want to pay more money for more reliable shipping.

So that is what's been going on at my end. Sorry for all the delays, and I really appreciate your patience over these past few months.


----------



## sos_nz

Thanks from me (and I am sure on behalf of many other current & future customers of yours) for the fulsome reply.

All the best with work, business & life. Without having been subject to the vagaries of USPS, I wonder if it's worth offering both options e.g. UPS and USPS, and the buyer can make the choice.

Anyway, will look forward to the next batch being released to the store


----------



## chrapladm

Well thats awesome to hear the update. I just ordered my Umik from Mini only because I wanted it soon. BUT I would have rather had the CS version. I will just wait and possibly order another around Xmas anyways from CS.


----------



## SRW1000

sos_nz said:


> Without having been subject to the vagaries of USPS, I wonder if it's worth offering both options e.g. UPS and USPS, and the buyer can make the choice.


This would be my preference as well. Some may be willing to pay an additional 5-10% for the more reliable shipping times, but others will be willing to wait the extra few days for delivery. If you were to offer FedEx or UPS, I'd bet that a lot of those customers would even opt for next day delivery.

For me, I'd just as soon save the $10, but the increase in loss/damage claims is certainly a concern. They can quickly eat up time and are a real hassle to deal with. If the trend continues, nobody would blame you for switching providers.

Glad to see you're business is busy, though! Managing growth can be a challenge, but it's better than the alternative.

Scott


----------



## Anechoic

sos_nz said:


> Without having been subject to the vagaries of USPS, I wonder if it's worth offering both options e.g. UPS and USPS, and the buyer can make the choice.





SRW1000 said:


> This would be my preference as well. Some may be willing to pay an additional 5-10% for the more reliable shipping times, but others will be willing to wait the extra few days for delivery. If you were to offer FedEx or UPS, I'd bet that a lot of those customers would even opt for next day delivery.


I agree this would be ideal, but it's not something we can accommodate right now. If we were large enough that we had an office with regular UPS/FedEx/USPS pickups it would be one thing, but offering customers a choice would mean a haphazard schedule of trying to arrange pickups from the various services or driving around town to make various dropoffs and it's not something we can do right now. Maybe in 10-12 months, but not right now, so it's really going to be about picking one service and sticking with it.

Thanks for the various well-wishes. We're trying to do better.


----------



## sos_nz

Well, all the very best with your decisions 

I'm allergic to paying excess postage (although do appreciate it's at cost to you). Some of the international shipping rates from premium shipping companies (e.g FedEx) make extortion look like the bargain of the century. That said, there are now reasonable USA postal forwarding services for we non-US buyers and I'm sure I could rapidly develop an allergy to lost / delayed parcels as well.

...speaking of which, I was thrilled to see my order for a UMIK-1 proceed this morning. Thanks for releasing the next batch to the baying mob!


----------



## arttu

I put in a order for one calibrated Umik a week ago when they were again availeble. Paypal sent me a message that it's payed but I didn't get feedback on a email or anything. I don't know if my order has been processed or not. All is well and some day there will be a delivery?


----------



## ronnies

After dilly dallying for about 6 months to order a umik-1 or not, I ordered one from minidsp and received the device today. I was expecting to see a USB thumb drive but could not find it. I come to this site to see whats going on and sure I was supposed to order it from cross spectrum Labs and not from minidsp directly. :crying:

Is it all lost?? Before I try to get in touch with minidsp and try to return it, can some one tell me if I am going to miss much by using this stock device as opposed to the one from CSL. I am still kicking myself for making this stupid mistake.

Regards
Ron


----------



## Anechoic

The factory calibration will get you in the ballpark.


----------



## ronnies

Thanks for the instant reply. Do you advice returning the stock Umik-1 and get the one from CSL? I am a newbie to all this and just want to know if it is worth to get the MOST accurate one or just be happy with the one which shows the ball park?


----------



## Anechoic

I am CSL, so it would be a little self-serving to recommend myself. The biggest differentiator between what I offer and the factor cal is that I provide off-axis calibrations that are more suitable to room/home theater calibrations, while the on-axis calls provide my MiniDSP are more suited for loudspeaker measurements. But for someone just starting out, I wouldn't sweat the details too much. 

Are you in the USA? If so and your mic is in "like-new" condition with all the accessories, I can offer you a trade-in credit toward one of my mics in return for your mic.


----------



## ronnies

Thank you. I will try to call you as I still don't qualify to use PMs.


----------



## Anechoic

Click on my name, go to the website and find the email contact form there. If you try to call me, you'll never reach me.


----------



## ronnies

Hi Anechoic

I left a VM for you earlier in the day ( before I could read your post) and just now sent an email to you from your website. Now that this is my 5th post, may be I qualify to start using the PM


----------



## mtbdudex

Hi Herb,
I've got 2 pre-USB Behringer ECM8000's!
1 w/o a cal file bought in mid-2008, then 2nd from you via CSL bought late 2010.

kinda getting tired of the whole mobile-pre & loopback thing when doing measurements, so possible time for me to get a USB mic, ha my 3rd mic. 
Any discount for a repeat buyer? :bigsmile:


----------



## mtbdudex

Well looking at CSL site appears the UMM-6 has issue with noise floor that the MiniDSP UMIK-1 does not, hence I'll get the MiniDSP UMIK-1 .

Herb - is the MiniDSP UMIK-1 noise floor confirmed on par with 30-40db of my ECM8000? 

http://cross-spectrum.com/measurement/calibrated_umik.html


http://cross-spectrum.com/measurement/calibrated_umm6.html


> What is the down side?
> There are two issues we have discovered with the UMM-6:
> 
> • The UMM-6 microphone has a relatively high noise floor of about 53 dB, compared to a noise floor of 30-40 dBA for the ECM8000 and EMM-6. This noise floor can cause issues with distortion measurements or measurements of quiet sources.
> 
> • The microphone may not work properly with software that expects the input device and output device to share the same clock source (for example, ARTA has issues when averaging multiple measurements with the UMM-6).


----------



## Anechoic

The UMIK-1 noise floor is on par with the ECM8000 noise floor (and slightly higher than the EMM-6 noise floor). Bad news is that I'm out of stock of UMIK-1 and since MiniDSP is also out of stock, I may not get any more until sometime in January.


----------



## mtbdudex

Anechoic said:


> The UMIK-1 noise floor is on par with the ECM8000 noise floor (and slightly higher than the EMM-6 noise floor). Bad news is that I'm out of stock of UMIK-1 and since MiniDSP is also out of stock, I may not get any more until sometime in January.


Ok - I'll place my order now and get it when available, thx.



> Your item(s) sold out
> We're sorry, the following item(s) isn't available at this time:
> 
> Calibrated MiniDSP UMIK-1
> Item number: umik1


:sad:


----------



## mtbdudex

Got a note fom CSL, MiniDSP UMIK-1 are back in stock!
I just placed my order :clap: 
Tomorrow I'll put my 2 pre-USB Behringer ECM8000's onto ebay...


----------



## Anechoic

No, no they are not! I had a few left over from the last batch that I'm releasing to folks who had expressed an interest (and for a couple of warranty exchanges), but once these are gone that's going to be it for at least a few weeks.


----------



## mtbdudex

Anechoic said:


> No, no they are not! I had a few left over from the last batch that I'm releasing to folks who had expressed an interest (and for a couple of warranty exchanges), but once these are gone that's going to be it for at least a few weeks.


sorry Herb for confusion :innocent: - and thx for getting mine out in this batch


----------



## Anechoic

It's okay, it's just that I've found that words on these forums tend to spread quickly and I want to head off the inevitable deluge of "I heard that UMIK-1s were in stock, but the site won't let me order, what's going on??" emails. :TT


----------



## Anechoic

Okay, MiniDSP informed me that a shipment is on it's way and should arrive mid-next week. We're taking pre-orders now and should start shipping by the 15th (hopefully sooner but I want to allow some cushion in case our consulting business flares up).

Thanks for your patience.


----------



## adickerson0

There is a lot of information out there, these seem quite popular, so sorry if you answered this else ware. I was wondering how difficult is is to switch between the 90°, 45°, and 0° modes? Do I need to load a calibration file for each one and switch between them depending on use?


----------



## Phillips

adickerson0 said:


> There is a lot of information out there, these seem quite popular, so sorry if you answered this else ware. I was wondering how difficult is is to switch between the 90°, 45°, and 0° modes? Do I need to load a calibration file for each one and switch between them depending on use?


Generally people use the 0 calibration file with the mic tip pointed towards (horizontal) the sound source, speaker etc. I tilt the mic very very slightly upwards.

Yes you load the appropriate calibration file and change the direction of the mic accordingly, e.g 45 degrees mic orientation with the 45 degrees calibration file loaded.

The difference between them is alot more in the high frequencies.


----------



## cavchameleon

Anechoic said:


> The UMIK-1 noise floor is on par with the ECM8000 noise floor (and slightly higher than the EMM-6 noise floor). Bad news is that I'm out of stock of UMIK-1 and since MiniDSP is also out of stock, I may not get any more until sometime in January.


Hi Herb,

I was just wondering if there is a good mic that you recommend with a lower noise floor (i.e. < 30dBA/dBC). I already have the UMM-6 (too high of a noise floor) and the ECM800 (both mics from you, thanks!!!). My main room is heavily treated and I used one of my large condenser mics to check the noise floor (dBA is 19dB and dBA is 28 dBC). My SPL meters also read as such, but they are really only calibrated accurately down to 30dbA.

I'm using this SBP Meter:

http://www.mcmelectronics.com/product/72-947

And this calibrator to confirm before:

http://www.mcmelectronics.com/product/72-7260

Thanks Herb!


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## NiToNi

Hi Herb,

If I buy an Audix TM1 online and have it sent to you directly, could you calibrate it for me, please...? 

Premium package of course.


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## Anechoic

Yes, we can do that, but it will be pricey (price of mic + $75 for the call + $20 shipping to UK). If you're still interested, send me a PM and we can talk specifics.


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## dalumberjack

Just went to purchase a UMIK-1 mic and saw they are still out of stock.

And idea when you will be getting more?

Thanks and can't wait to get mine!


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## coyotearms

I received my MiniDSP UMIK-1 a couple of days ago (great turn around time!) and cranked out some spectra of my AV room using it and a NuForce 192s USB to S/PDIF. I ran identical cases except for which calibration curve was used, the one from CSL (narrow band 90 degrees) and the only one from MiniDSP which I understand is the equivalent orientation (and obtained off their site for my serial number). While the trends in the two spectra were the same at low frequency, I noticed there was 4 or 5 dB differences, which is also seen from the two calibration curve files (only comparing them for fairly low frequency). 









I was a bit surprised since I was expecting closer agreement but happy to have a wider frequency range and three angles done at CSL. Am I missing something, or is there some way to interpret the Sens Factor included in the MiniDSP file to explain the differences. I checked that REW does not do anything with Sens Factor as only lines that start with a number are read into the program. Anyone have any ideas?


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## NiToNi

Anechoic said:


> Yes, we can do that, but it will be pricey (price of mic + $75 for the call + $20 shipping to UK). If you're still interested, send me a PM and we can talk specifics.


Hi Herb,

I sent you an email via your website about a fortnight ago but still haven't heard back from you.

I am good to go on this so please get in touch.

Thanks,
Nick


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## Nec

Hi all, just receive my umik-1 from cross-spectrum today need info regarding first time using mic with rew.For the first time do I need to go minidsp to download the calibration file? Or it plug and play. Thx in advance.


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## GCG

PnP except for level (SPL) considerations. The CS calibrations don't contain the sensitivity info REW needs. There is a fix for this and it does come from the MiniDSP Cal file. The MiniDSP cal file contains, as the first line, sensitivity info in a form REW can use. Simply download the MiniDSP file and copy and paste the first line from it into the first line of the CS files. You'll be good to go.


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## Nec

Hi GCG, I already download the minidsp files, so I just copy the first line of the file sens factor and serno. Where should I paste to? Sorry for the trouble cos still new with rew and umik mic.Thx a lot.


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## Nec

Also from the cross spectrum it come with USB, for the USB is it just info only? Or something than I can use it on rew? Thx.


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## redsandvb

Nec said:


> Hi GCG, I already download the minidsp files, so I just copy the first line of the file sens factor and serno. Where should I paste to? Sorry for the trouble cos still new with rew and umik mic.Thx a lot.





Nec said:


> Also from the cross spectrum it come with USB, for the USB is it just info only? Or something than I can use it on rew? Thx.


On the USB stick from Cross Spectrum there should be some files w/ calibration results. Copy the 'narrow_band_response' ones to your hard drive, then open with a text editor, like Notepad/Wordpad if using Windows, and paste the sens factor line from the MiniDSP file to the top (as a new line). Then when you use REW you point it to the file you edited when it asks for calibration file. That's what I did.


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## Nec

Hi redsandvd, from the USB file it got narrow band 0 degree ,45 and 90 so which files should I paste to? It also got one third octave band response 0 degree,45 and 90 for what use? So any one got guide line or manual to follow cos I abit lost already. Thx .


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## Nec

And i using windows, thx.


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## redsandvb

I used narrow band 0 degree and 90 degree, did not use others. 0 for measuring individual speakers and 90 for subwoofer. I don't remember where, but I read it in one/some of the posts on this forum.


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## htsnube

Delete, thanks


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## compaddict

So with REW I load the narrow band and angle of choice?
TIA,
Vince


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## havnjero

ahh! I should have claimed a discount here!

oh well. the snappy service is worth the extra bucks 

emailing with you now herb, with the subject "FRD F.A.?"

thanks!


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## finalrinse

Hello, I just tried to order a UMIK-1 mic from Cross-Spectrum but during checkout I was rejected and it said sold out! I could not even reserve one. Any ideas when I might be able to get one?
Thanks,
Tom


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## GCG

finalrinse said:


> Hello, I just tried to order a UMIK-1 mic from Cross-Spectrum but during checkout I was rejected and it said sold out! I could not even reserve one. Any ideas when I might be able to get one?
> Thanks,
> Tom


WAIT.
They sell out each run quickly. You'll thank yourself.


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## finalrinse

GCG said:


> WAIT.
> They sell out each run quickly. You'll thank yourself.


Thanks, I'll keep checking


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## Niick

Hello everyone, 
this question is for Herb, or anyone really who knows the answer. I purchased a calibrated UMM6 from cross spectrum about 6 months ago or so and have been extremely pleased with the mic and service recieved from Herb/Cross Spectrum Labs. I use my UMM6 roughly 2-3 times a week at work (Custom car audio installation), and every now and then i bring it home with me on my days off to experiment with test and measurement, and to learn Smaart 7, (upgraded from 6, finally!!). Regarding transporting the mic, i often toss it in the side pouch of my laptop instead of keeping it in the case. How does the way we handle and transport the mic affect its accuracy and if it is damaged will it be grossly inaccurate or can it be thrown off by a tiny percent?


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## Anechoic

Hey all,

It's been far too long since I've posted here, I can't believe how fast time flies.

First off, Happy New Year to all. Thanks for all of the support, and please keep those discount requests coming!

Second: I just wanted to let folks know that we're selling the MiniDSP 2x4 digital signal processor unit. And as with the other products we sell, you HTS folks can wet your beaks a little - leave your HTS username in the "Instructions to Merchant" field and we'll refund you $5.

We're starting slow right now just to make sure we can handle the support aspect of selling these so we'll likely run out of units quickly. Once we're comfortable, we'll start selling them in volumes.

Carry on!


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## W3Rman

Question about the sensitivity information being missing from the CSL umik 1 calibration file.

*I have created a collated file that has both the miniDSP and CSL data*
> the miniDSP has sensitivity information ( I really like not having to calibrate the SPL with my Galaxy 140 every time I plug in the mic)
> the CSL has better low/high frequency range and also is accurate for my specific mic

So the file i created has all data from both files interwoven within. Using this file REW does not require to calibrate every time I plug in the mic for accurate SPL readings.

*Concerns:*

There is no parsing errors from the new file when REW starts but I wonder if some lines are just being looked passed with "False-Negative" results

*Questions:*

A. What does the second column of data actually represent in both these calibration files? Because if it is sensitivity data then both files have this data and why then would the CSL cal. file not then allow REW to avoid this step thus requiring me to use my SPL meter.

B. What does the third column of data represent in the CSL calibration file? This column only has zero's and it is not present in the miniDSP file.

C. How does REW parse the data in this calibration file? Does it consider any "white-space" to be the same as "tab" and the same as "Line Return" as being next data to process?

*Here attached is a sample of screenshots of the file I have created. *
> The CSL file are the lines that have the third column of zeros
> The miniDSP file only has two columns of data


*!.. [edit] ..!* ... I obtained some answers :nerd:


The first line of the miniDSP calibration file is the actual sensitivity information.
The second column in both CSL/miniDSP files is level difference in dB from the reference mic
The third column in the CSL file is the phase used


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## Anechoic

W3Rman:

A: the second column (of both mic files) is the relative response of microphone, in dB relative to 0 dB at 1,000 Hz. It is *not* the mic sensitivity. To obtain the sensitivity at each frequency, the relative response needs to be scaled by the sensitivity.

B: the third column is there because some programs expect to see a column for phase data and will report an error if provided with only two columns of data. Because we don't measure phase for the microphones, we just report "0" for the phase data.

C: I'll let John handle the specifics wrt to REW, but I think (again, confirm with John) that REW treats tabs and spaces as an identical delimiter and treats CR/LF (in various combos) as end-of-line.

Also (for those that may not be aware): CSL calibration files generated after January 2016 for UMIK-1 and UMM-6 mics include the *factory* sensitivity data in a separate set of calibration files in a "REW" directory on the USB stick. Again, these are the factory values, CSL does not vouch for these figures and does not support these values. They are there because a lot of people want it.


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## W3Rman

*^ ^*
:jiggy: 

Thanks for clearing these details up with me


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## TigerGenetics

Sorry for the thread revive, but I'm curious if the calibration service is still available? I have a current UMIK-1 and would like to send it in for calibration. Am I still able to do so?


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## cichlids

Hope this makes sense fingers crossed??? I would like to get my Umik-1 mic re calibrated. I sent Herb some messages he answered some but not all, for those that have one of his mics if you are using it along with REW will you get a sweep that goes below 10hz?? The mic I bought along w/ the bal. minidsp seems to hit a wall at 10hz.I would like to see if my subs will go lower.


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