# Getting started



## Scubasteve2365 (Mar 15, 2013)

I'm sure there are a ton of these threads. I've been reading here for 2 days and I'm still not confident in my selections.

*Goal*
Acquire suitable equipment to take required measurements of my theater room to aid in treatments and EQ'ing. I am currently building a quad FiCar 18" infinite baffle manifold (waiting on drivers) and integrating that will be my first effort

*Equipment*
I can see and appreciate the ease of buying a USB mic, but I think I'd like to go the USB Preamp route. The reason being is that I am an amateur (very amateur) acoustic guitar and vocals player and buying a simple preamp would allow me to do some very portable recording with other microphones that I own suited for those tasks.

For now I'm thinking:
*
Mic Preamp* - Behringer Xenyx Q502USB Mixer or the ART USB Dual Pre. (The looks of the Behringer product looks better IMO)
*Mic* - Dayton EMM6 from Cross Spectrum

*Use*

For convenience reasons I would like to use my primary laptop which has the traditional setup of analog mic-in (with labeling to indicate line-in) and headphone out. No HDMI. Going the USB Pre I don't think I'd even be using any of these ports as the USB Pre would serve as the audio output connection as well. The USB Pre becomes essentially an external soundcard if I understand correction?

*EQ*

I am undecided on EQ but for now I like the look of the MiniDSP. I will have a Behringer EP amp (or iNuke line) to drive my sub. I have a Yamaha AVR from my Klipsch arrangement. (RF-5 main, RC-7 Center, RS3 side and rear surrounds).

I'm assuming that I can't do any real EQing of any speaker being driven by the Yamaha AVR, other than what options might exist in the AVR itself. If that's the case, I want the flexibility of having separate power amplifiers down the line. Are there 7 input/7 output DSPs for EQing a full 7.1 arrangement?


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## Wayne A. Pflughaupt (Apr 13, 2006)

Welcome to the Forum, Scubasteve!




Scubasteve2365 said:


> For now I'm thinking:
> *
> Mic Preamp* - Behringer Xenyx Q502USB Mixer or the ART USB Dual Pre. (The looks of the Behringer product looks better IMO)


 Some of these devices seem to have trouble with REW, so you might do a search to see if someone here has successfully used that particular Behringer. If not, you’re taking a chance with it. The ART will be just as useful after REW as the Behringer as a recording interface – I use my TASCAM US122 pretty regularly.




> The USB Pre becomes essentially an external soundcard if I understand correction?


That is correct.




> I'm assuming that I can't do any real EQing of any speaker being driven by the Yamaha AVR, other than what options might exist in the AVR itself.


Which Yamaha AVR do you have?

Regards, 
Wayne


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## Scubasteve2365 (Mar 15, 2013)

I have the Yamaha RXV-667

http://usa.yamaha.com/products/audio-visual/av-receivers-amps/rx/rx-v667/?mode=model

It has some CinemaDSP stuff. Something I never use and likely never will. Don't think there are any adjustable EQ functions. 

I don't understand why the Behringer Q502 wouldn't work. Is there something specific about REW? I mean, if Windows sees the unit and brings the audio in, why wouldn't it work? The benefit of that model over both the ART and Tascam appears to be that it's more adjustable and cheaper. The Tascam is twice the price everywhere I looked.

It looks like they make a phantom powered Q302USB that my local guitarcenter might stock starting next week. If that's the case I guess I can do a no risk trail. I won't have acquired a calibrated mic yet, but if I connect any old mic and get a signal into REW I can assume it "works" right?


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## AudiocRaver (Jun 6, 2012)

Scubasteve2365 said:


> I don't understand why the Behringer Q502 wouldn't work.


Everything about its specs and features and the way Behringer tends to go about their designs says that it should work just fine with REW, and I am fully confident that it will. Especially with Windows. (The Mac OS is known to have its quirks with some audio interfaces.) But no one has verified it yet. Wanna go first? Have no fear. Betting is not allowed, of course, but if it was..... I am sure it will work fine. _Now don't embarrass me._


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## AudiocRaver (Jun 6, 2012)

Scubasteve2365 said:


> It looks like they make a phantom powered Q302USB that my local guitarcenter might stock starting next week. If that's the case I guess I can do a no risk trail. I won't have acquired a calibrated mic yet, but if I connect any old mic and get a signal into REW I can assume it "works" right?


The Q302 is known NOT to work with REW. I read it in another forum and forget the exact details, but I believe it had USB into the computer but no USB path out or something like that.


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## EarlK (Jan 1, 2010)

> I don't understand why the Behringer Q502 wouldn't work. Is there something specific about REW? I mean, if Windows sees the unit and brings the audio in, why wouldn't it work? The benefit of that model over both the ART and Tascam appears to be that it's more adjustable and cheaper. The Tascam is twice the price everywhere I looked.


- No one can make decent REW measurements if the acquired signal ( the input ) is automatically fed back into the output ( that is then,"re-acquired" again , & again & so on ) .

- ( So ) just how do you propose stopping that process from happening with the Q502USB ( when by default, it'll place the input signal onto the same buss as your output signal ) ?

:sn:


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## Scubasteve2365 (Mar 15, 2013)

EarlK said:


> - No one can make decent REW measurements if the acquired signal ( the input ) is automatically fed back into the output ( that is then,"re-acquired" again , & again & so on ) .
> 
> - ( So ) just how do you propose stopping that process from happening with the Q502USB ( when by default, it'll place the input signal onto the same buss as your output signal ) ?
> 
> :sn:


Wouldn't the same problem exist with the other USB Pre/mixers like the Tascam unit?


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## EarlK (Jan 1, 2010)

Scubasteve2365 said:


> Wouldn't the same problem exist with the other USB Pre/mixers like the Tascam unit?


Just about all the lower-end soundcards have a way of dealing with this question .

- The higher end cards approach the problem within dedicated software for the card . Like this ;










It's called the "Monitoring" feature ( or something meaning the same ) .

Here's a pic of the Tascam ( 144 ) & it's monitoring ( mix ) feature .










Here's the ubiquitous Behringer UCA202 & it's ( simplistic ) monitoring ( mix ) feature ( it should be "off" ) .










If you can find a way to have the Q502USB emulate the routing features seen in the above examples, then you're good to go .

:sn:


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## Wayne A. Pflughaupt (Apr 13, 2006)

AudiocRaver said:


> The Q302 is known NOT to work with REW. I read it in another forum and forget the exact details, but I believe it had USB into the computer but no USB path out or something like that.


Yup – the sound card has to be full duplex, meaning it has the capability to take care of inputs and outputs simultaneously via USB. I don’t know whether or not the 502 has this same issue as the 302., but I’ll bet there’s a good chance it does, since the two are virtually identical, save the number of inputs.

Scubasteve, your best bet would to be to stick with something “tried and true” from the REW Soundard Database.

Regards, 
Wayne


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## Wayne A. Pflughaupt (Apr 13, 2006)

Scubasteve2365 said:


> I have the Yamaha RXV-667
> Don't think there are any adjustable EQ functions.


According to Pg. 87 of the manual, there is an adjustable parametric EQ. A lot of Yamaha’s recent-model receivers have some pretty powerful manual PEQ features. Might want to check it out – if it’s good enough you wouldn’t need outboard EQ for the main channels.

Regards, 
Wayne


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## Scubasteve2365 (Mar 15, 2013)

Wayne, thanks for the note on the Yamaha. Been awhile since I looked at the manual and when I did EQ wasn't a thought. Was going to look at it later today but got distracted with the USB Pre research. 

I did find this video and I think the user did a great job breaking down the device. Unfortunately he did not do it with the 502USB. 

http://youtu.be/pmKdOm7oibM

The hang up here is that you cannot shutoff the mic input from the main line level output. You can however redirect the computer output over USB to the headphone output but because you can't cut the mic input from mixing in either output (main or phones) the device won't work. That being said, couldn't you just use the headphone output of the pc/laptop directly?


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## Scubasteve2365 (Mar 15, 2013)

Let me shift gears a bit. Might have been searching for a solution to a problem that doesn't exist in the first place. 

Since the USB mics, such as the one from MiniDSP cost near what the non-USB mics do, perhaps I just buy one of those and bypass the whole 302USB type device when using REW (I'd still buy such a device for the other purpose I have). Perhaps I'd have my cake and be able to eat it too. 

The question is then, why do some say one needs an HDMI output when using a USB mic?


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## AudiocRaver (Jun 6, 2012)

Scubasteve2365: Behringer does not publish a schematic or functional block diagram for the Q502USB. Until someone tries it out, we will not know for sure if it works with REW. Users seem attracted to it for numerous reasons - for use with REW, as a portable micro mixer/recording interface... I eyed it myself for that at one time. For now we are not sure, just giving well-educated guesses. Let us know what you decide and how it works for you.


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## AudiocRaver (Jun 6, 2012)

Scubasteve2365 said:


> The question is then, why do some say one needs an HDMI output when using a USB mic?


It depends on the accuracy you want. If you use a USB mic with a laptop analog output, the high- and low-frequency rolloffs through that output are unknowns, and while outboard audio interfaces are usually pretty flat, the budget circuitry of an onboard audio interface might not be at those frequency extremes. I usually advise not to go that way because I don't like unknowns like that. Others will tell you not to worry about it. It is probably not a big deal 92.713 per cent of the time (a rough estimate), but I tend to be kind of conservative about things like that, so that is what I advise.


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## Scubasteve2365 (Mar 15, 2013)

AudiocRaver said:


> It depends on the accuracy you want. If you use a USB mic with a laptop analog output, the high- and low-frequency rolloffs through that output are unknowns, and while outboard audio interfaces are usually pretty flat, the budget circuitry of an onboard audio interface might not be at those frequency extremes. I usually advise not to go that way because I don't like unknowns like that. Others will tell you not to worry about it. It is probably not a big deal 92.713 per cent of the time (a rough estimate), but I tend to be kind of conservative about things like that, so that is what I advise.


Is this true when using the analog out in general or is this a property of using the USB input combined with the onboard analog out?


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## AudiocRaver (Jun 6, 2012)

Scubasteve2365 said:


> Is this true when using the analog out in general or is this a property of using the USB input combined with the onboard analog out?


It is only a concern when USB input is combined with the onboard analog out. With an analog mic, you run the sound card calibration process which ends up compensating for the _combined_ input/output rolloffs. It is an all-electronic closed-loop process that isolates your sound card characteristics accurately, but by its nature you can't tell how much of the error being compensated for is from the input and how much is from the output.

Here is the loopback calibration curve for this budget laptop I use for foruming. REW takes very little horsepower, so it runs very nicely on it.

 

Using a USB mic and analog output and no calibration file, high-frequency accuracy is excellent beyond 20KHz, no problem. To analyze and EQ down to 20 Hz, the combined error input plus output is less than 1 dB. There is no way to know how much of that error is due to the output and how much is due to the input. When both are in use, as with an analog microphone (we are equating this to the use of a sound card with microphone preamp, phantom power, etc.), using the calibration curve cancels it all out and we have no inaccuracy due to the soundcard rolloffs. Using a USB mic, the worst-case possible rolloff due to the output stage is less than 1 dB, good enough, so you don't worry about it.

If you want to calibrate your sub down to 10 Hz using a USB mic, the error could be as much as 2 dB, still not terrible. If you have a really nice sub and want to EQ down to 5 Hz, your error could be as much as 6 dB, that is getting significant. If you just invested in a super subwoofer and want to calibrate it down to 2 Hz (and you have a really nice mic), you could be off by as much as 17 dB. How much is due to the output? You can only guess. It is a fairly good educated guess that the input is probably a bigger contributor to that error then the output, that is why we normally advise not to use a calibration file when using a USB mic - because you probably have less error without the calibration file then with it. Probably. But how much error do you have due to the output stage alone? 2 dB, 8 dB? You do not know. Willing to just play with it and see what you come up with? No problem. How particular are you, how critical is it to you? A lot of us obsess over 1 dB of error. Someone may have many thousands of dollars invested in their system and they just _want to know._ Others will accept a few decibels of error at that extreme frequency. Someone else may be setting up to mix for a movie, and may need 1 dB accuracy.

Again our advice is not to use a calibration file with the USB mic, the reason being that it is a _best educated guess_ that you will get less error due to output stage rolloffs without the calibration file than you will get with it. But how much will it be? You do not know. That is why my advice is normally not to use a USB mic with an analog output, because without knowing more about the individual situation, how low in frequency they want to go, how critical the accuracy is to them, it seems the safer approach. Of course, this is all for fun, it is all recreation, not life and death, but still when we get done we want it to _sound good,_ that is why we are all tuned in to HTS in the first place. So it does matter a little.

Two more thoughts and then I will shut up. Promise. For now.

If no extreme frequency measurements are involved, just 20 to 20 kHz stuff, the chance of very much error is pretty small, so USB mic with analog output is relatively safe.
If you want an extra degree of comfort, run the calibration curve on the computer's onboard sound circuits, save it or print it out, then back the calibration file out of REW so it is not active. Now you know what your worst-case error could be at the extreme frequencies and as you look at further measurements you can take that into account.
That was the long answer to your question. Begging your pardon, I am not very good at giving short ones.:bigsmile: I suppose it would have been, "It is only a concern when USB input is combined with the onboard analog out." But where is the fun in that?


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## Scubasteve2365 (Mar 15, 2013)

Thanks, I appreciate you taking the time to explain it. You see a lot of suggestions made without the background explanation a lot.

Fortunately, I have a PC near my theater that I use as a home server (Win8, storage pool feature) for my wife's backups (She's a photographer" and to serve up my digital media to my popcorn hour and the like. That machine has an HDMI output. Downside is that it's a headless machine and it'll require a USB extension for the mic that might push the recommended limit. I had hoped to use my laptop. I might just use both so I can see the difference.

I just bought a UMM-6 from Cross Spectrum.

Thanks for you and everyone else for the help.


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## Scubasteve2365 (Mar 15, 2013)

OK,

Now that I bought the Cross Spectrum calibrated UMM-6, which is calibrated a 0, 45 and 90 degrees. What is the best method for taking readings at the listening position. I'll probably just measure and calibrate at my listening position (screw everyone else  ). I already have a boom mic stand. I very rarely listen to music in my theater and if I do it's not critical listening. Where should the mic point?


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## Wayne A. Pflughaupt (Apr 13, 2006)

I prefer the mic pointing at the speaker to be measured, perhaps tilted up 20 degrees or so. Use the 0-degree calibration file for this. That's for full-range measurement; for subs it doesn't matter where you point the mic.

Regards,
Wayne


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## AudiocRaver (Jun 6, 2012)

Scubasteve2365 said:


> Downside is that it's a headless machine and it'll require a USB extension for the mic that might push the recommended limit.


You might grab a USB repeater cable. They don't work for all things USB, but they seem to work great with USB mics.


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## steamshovelman (Apr 12, 2013)

Hi Steve, I just joined the Shack hours ago after a google search on room equalization and finding REW. Ordered a Cross Spectrum calibrated UMM-6 to go with my HDMI laptop (also running Intel wireless HDMI WiDi!) and started poking around to learn more about using REW while waiting for the mic and found this thread started by you with a Yamaha RX-V667, same as me as well! So looking forward to any updates you have. <biggrin> Larry


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