# New UMIK-1 and REW 5 - "Level is low"



## ronanmcallister (Jan 29, 2013)

Hi all,

Thanks to the author of REW and others here for the great software and I appreciate your help.

I've got a new UMIK-1, with REW 5.0 and I'm using the mic cal file from MiniDSP for my mic. I've got:

XP SP3 HPQ laptop
External USB audio interface, E-MU 0204 used as output to preamp.

The below should not matter as I think this has to do with the mic cal or how it works with REW:

Magnepan MG3-A (used above 120hz)
Heil horn tweeters (custom made some years ago, using high-pass 6db/octave capacitor filter)
18" subwoofer (120hz and below)

Everything but the Heils are electronically crossed over, using active Xovers, nothing fancy, pro-sound PA amps powering everything.

I'm trying to do some basic frequency response measurements after having read (well closely perused) the documentation. As I understand it, the USB mic with it's cal file, should not require I use an external sound level meter, and I hope/think this UMIK and REW is designed to work together.

What I observe, is when I calibrate the sound card (correctly configured in XP, and after making loopback connections, saving the cal file) and configuring the UMIK cal file, I can only get a freq response sweep to work when I move the mic very close to the speakers AND turn it up almost too loud. I always seem to get "Level is low" (something like -50db) when I have my stereo system turned up REALLY loud and I try to make a measurement (making 10-20Khz sweep). 

I've got my mic input (in WIndows) for the umik set to max BTW.

WHen I move the UMIK back to listening position, or anything over 3' or so, I have to crank the stereo in order that it will sweep. Good thing the Maggie's need to be rebuilt anyways, as you can really hear them rattle, along with the windows.

As a "sanity check" I put my Radio Shack SPL meter next to the USB mic and ran some pink noise from REW into the system, both REW SPL and my Radio Shack meter are very close ( BTW I am not interested in absolute SPL measurements, only frequency response, IR, phase, etc.

Is there any known issue with 5.0 REW having to do with the UMIK-1 input level? I suppose I coulld try my Bheringer ecm8000 mic, feeding it into my E-MU 0204, but it has NO cal file and I'd rather use the usb mic. 

BTW my USB mic was received without any physical damage.

Thank you in advance

ROnan McAllister
Meadow Vista, ca


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## sonic_blue (Jan 24, 2013)

ronanmcallister said:


> As I understand it, the USB mic with it's cal file, should not require I use an external sound level meter


Correct, and in fact in the latest Beta13 version of REW (which you should use as it has some umik1-specific corrections) it does not let you even calibrate SPL externally because it gets that from the calibration file (serialno.txt file).



ronanmcallister said:


> when I calibrate the sound card (correctly configured in XP, and after making loopback connections, saving the cal file


You're not supposed to calibrate the sound card or make a loopback as you aren't using the soundcard to record from a mic, as you are using an external USB mic. So that step should be skipped entirely. See the help file within REW, it tells you which steps you can skip if you are using USB mic.




ronanmcallister said:


> I always seem to get "Level is low" (something like -50db) when I have my stereo system turned up REALLY loud and I try to make a measurement (making 10-20Khz sweep).


I believe that is -50dB*FS* which is (if I'm correct) the digital level that the mic is measuring and has nothing to do with the dB being heard in the room. 

Also REW will warn you if the sine sweep measurment is under 90dB when doing a frequency response measurement. 

Perhaps if you could post your frequency response chart so that you can see what your actual room dB is, not the -dBFS that the mic is reporting.

Having said that, I do feel that my umik1 is measuring dB lower than it actually is , as with my speakers turned up to a somewhat deafening level the frequency response chart is still only saying ~80dB max. 

*I think, ultimately, we need to be able to do a SPL calibration in REW to make sure the umik1 level is reading correctly.*

Either that, or I'm just extremely sensitive to volumes > 80dB? :huh:


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## sonic_blue (Jan 24, 2013)

Postcount+1 so that I can post links : )


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## AudiocRaver (Jun 6, 2012)

The following quote is from this thread about the UMIK-1:

"The UMIK-1 can handle signal levels up to 130dB, but that means at normal measurement levels you will get warnings from REW about the input level being low. You can ignore those warnings."

If you are using a good listening level, you should be fine. The often recommended level is 75 dB. A level of 80 dB to 85 dB is often used but if there are big peaks in your frequency response curve, you may end up driving your system pretty hard at those peaks. I like to start out with a lower level for that reason.


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## ronanmcallister (Jan 29, 2013)

Thanks everyone for your help -- I've attached an image using 5.01 beta 13.2863 showing my quick test nearfield at approx 3ft (brown trace ) and at listening position (green trace). The new software seems to work much better for me, I really appreciate everyone's input as it's so easy using REW with the external USB sound for output and UMIK-1 USB mic. The sweeps were not uncomfortable to listen to in the same room this time. :sn::sn:

If anyone has the inclination to look at the measurement files please let me know, I can upload them. I may be missing something in my quick check.

Now I need to keep reading and learning so I can understand how to interpret the readings and turn my interpretations into meaningful changes to my room / sound system. So far I'm only looking at the sweeps. For sure I think I need some bass traps and I KNOW my room's too small (12W x 15L) and I've not yet invested in an EQ, as I'm using a combination of my preamp controls (Yamaha C-2) and various padding and electronic crossover controls, amplifier input levels, for tone adjustments (to be honest I come from analog days, need to justify the need for newer EQs using DSP, etc). 

At a minimum, 'out of the box', REW has confirmed the hole I knew I have had, now I need to set about fixing it. I'll probably build some upper-bass / lower mid drive units, and go for 3-way active, as I strongly believe your system must be basically able to be swept flat prior to equalization, DSP, etc, at least near-field. 

Thanks again for the help and any other ideas you may have.

Rgds, Ronan


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## sonic_blue (Jan 24, 2013)

ronanmcallister said:


> and I've not yet invested in an EQ


I would highly recommend minidsp 2x4 as that's what I'm using to correct a huge 12dB "hump" in the 100-300hz bass on my audioengine speakers. The improvement in bass quality is amazing for me 

Also the minidsp software is designed to be used with REW as you can just import the biquads that REW has calculated straight into minidsp:


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## ronanmcallister (Jan 29, 2013)

Thanks!

Makes me wonder what phase funnies are happening when DSP does whatever it must to try to EQ.....

I keep coming back to wondering how far one can/should go with speaker type/placement/tweaking, room treatment, etc prior to using DSP. A friend has a "drive rack" (DBX) which seems to do a pretty good job of EQ'ing his system flat, although it runs out of gain in certain areas. I've not yet tried it.

I appreciate everyone's thought

Ronan


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## luke202 (Jan 11, 2013)

New Here. Just downloaded REW. Looking to use the UMIK-1 mic also. This was helpful. Thanks


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## ronanmcallister (Jan 29, 2013)

*Re: New UMIK-1 and REW 5 - "Level is low" (Now - RTA/spectrum shows signal when no sound present)*

View attachment 40601
Perhaps I should start another thread?

Today I'm playing with an old-school analog EQ (yamaha 10band) trying to see how much I can flatten out the sweep -- in doing so, I played with the RTA function and have noticed something strange.

Note the attached screen shot wherein my room is basically silent (except an occasional stomach growl) -- my radio shack SPL meter doesn't budge. The RTA (spectrum or RTA) shows 60 DB (approx) whereas "levels" show approx -85DB which is what I expect. 

I have checked using WinAudioMLS (screen shot attached) RTA, which does not show this "measurement but no sound" anomaly (or misunderstanding on my part).

Can the REW RTA spectrum/RTA be "normalized" to be closer to what the "Levels" show? Where does this false signal emanate from?

I'm still using the UMIK-1 with latest beta. I have only added the yamaha EQ and as I said I have no sound present other than very slight background.

THank you
Ronan


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## JohnM (Apr 11, 2006)

*Re: New UMIK-1 and REW 5 - "Level is low" (Now - RTA/spectrum shows signal when no sound present)*



ronanmcallister said:


> Can the REW RTA spectrum/RTA be "normalized" to be closer to what the "Levels" show? Where does this false signal emanate from?


The level shown in the RTA display (number at top right) should be the same as that shown by the SPL meter with 'Z' (i.e. no) weighting. If there is significant low frequency noise (acoustic or electronic) that will lift the SPL figure accordingly. To see dB FS figures instead of dB SPL, select dB FS in the drop down at the top left of the graph, which is shown when the mouse is within the graph area. To have the RTA trace drawn at levels that reflect the bin energy, untick "Adjust RTA Levels" (but that will not alter the overall figure shown, only the level at which the graph is drawn).


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## sonic_blue (Jan 24, 2013)

ronanmcallister said:


> Makes me wonder what phase funnies are happening when DSP does whatever it must to try to EQ.....


I'm guesssing the same kind of "phase funnies" when digital EQ's are used all the time in music production? :scratch:

This article seems to be implying that EQing doesn't actually harm the sound at all.

I certainly can't hear any such distortion, nor can I measure it in a frequency response comparison with the minidsp removed from the chain.


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