# Discuss mic options for use with REW software



## fastline (May 7, 2010)

I have used the REW sofware a bit with various mics. I have yet to buy anything specific. My concern is that we end up putting a TON of faith in what that mic is sensing and the software is saying so I would like to make sure I get some half way decent equipment. 

I recently bought a Pioneer Elite SC-07 with auto calibrations and it did NOT really ice the cake for me. That got me really wondering how accurate mics will be. Especially when I see that the radioshack meter must be calibrated and in some situations, modded to perform decent at lower frequencies. 

I would really like to get an SPL type meter since they could also come in handy for other testing as well. I simple mic would be dedicated but with the software, would probably be a better setup anyway. So,,, while mentioning "budget minded", what should I use? I really need to calibrate the subs as well and plan to use the behringer for that. I was going to setup both my 18" the exact same and split a mono cable to each of them.


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

Any mic used for frequency response measurement needs a calibration file. Back in the day, hardware real time analyzers came with specific measurement mics that had their calibration built into the hardware itself. With programs like REW you’ll get the most accurate results with a mic that has had a custom calibration file generated by a specialist in that field, especially if you’re interested in accurate full-range readings.

However, from your post it sounds like you’re only interested in measuring subwoofer response. For that, the Radio Shack SPL meter and our calibration file will work perfectly fine.

Regards,
Wayne


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## fastline (May 7, 2010)

Sorry, I was probably misleading in my previous post. I am wanting to test full range. I suspect I will not be happy with how my receiver tunes the system and will resort back to manual tuning by simply going through sweep test with REW and tuning accordingly. 

I am not super concerned that I have the absolute most accurate thing going but I would like to be in the ballpark. My ear will ultimately determine what I like. 

I am still a little unclear how to tune all 5-7 channels of a surround system though. Is each speaker tuned individually or are they done together? My receiver has some nice ability to tune say the mains, then tune others to somewhat match them. 

It also has some type of "timbre matching" ability but I am not real sure how it would do that. IMO, timbre match can only be accomplished by using similar or identical speakers since all speakers have their own character. 

I am still trying to determine if and how I might use the auto systems of the receiver and which would be manually adjusted.


EDIT: Keep in mind that I will only be using a behringer device for sub frequencies and the rest will be tuned with the receiver.


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

> I am not super concerned that I have the absolute most accurate thing going but I would like to be in the ballpark.


I’d suggest that “in the ballpark” isn’t good enough for full range measurements, as a couple of dB one way or the other is enough to make an audible difference. If you’re going to make an effort to equalize your main speakers, you want an accurate frequency response chart to work from. Otherwise you might end up equalizing a “problem” that doesn’t exist, or ignoring one that does.

Naturally, what will make or break an accurate reading is the measuring mic and its calibration file. We do offer a generic calibration file for the Behringer ECM8000 and Dayton EMM-6 mics, but I wouldn’t use that for equalizing. As you can see from this graph that shows the variations in response compiled by numerous mics, there’s no telling what you’ll get with a generic file.










If you want accuracy, your best bet is to spring for a calibrated mic from our preferred vendor, Cross Spectrum Labs and a USB audio interface such as the Tascam US122, M-Audio Mobile Pre, etc., that’s compatible with your operating system. A cheaper alternative to the interface, albeit more difficult to connect and operate, would be the Behringer UCA202 soundcard and XENYX 502 mixer w/ mic preamp and phantom power, assuming the former is compatible with your operating system.




> I am still a little unclear how to tune all 5-7 channels of a surround system though. Is each speaker tuned individually or are they done together?


They should be measured separately, but above ~500 kHz any equalizer filters should be identical for the front L/R speakers.

Regards,
Wayne


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## fastline (May 7, 2010)

Thanks for all the helpful info. Those mics look great and pricing is in line though I did submit a form to see about any discounted units. 
I am curious why I would need a USB inserface for these? I had planned to use one with my laptop and insert into the mic input. Is that not acceptable? 

Also, from what I understand, any audio lab can calibrate a mic as long as their testing mics have ANSI traceability? Is that accurate? Just thought if I could find a used Dayton, I might see if someone local was doing calibrations.




EDIT I also have the calibration mic from my receiver. They look a little cheesy IMO and not sure if they are worth tuning or not. Could this be an option?


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

> I am curious why I would need a USB inserface for these? I had planned to use one with my laptop and insert into the mic input. Is that not acceptable?


The interface provides both a mic preamp and phantom power. In the unlikely event that your laptop mic preamp provides phantom power, there is also the issue of generating a calibration file for it. Calibration files are typically only possible with line inputs and outputs, not with mic pre’s.

Regards,
Wayne


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## fastline (May 7, 2010)

Gotcha on the phantom power. However, still a bit in the dark regarding creating a calibration file. Could you better explain that as well as why I would want or need to if I have someone else do a calibration? I suspect you have to have an ANSI traceable mic to test against and controlled conditions for the testing. 


Also, could you advise on the receiver mic that I have? Are these not worth the plastic they are molded from? These head units are all now calibrating everything based on these mics. Just curious if they could be used for this purpose if there were a calibration file created for them?


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

> However, still a bit in the dark regarding creating a calibration file. Could you better explain that as well as why I would want or need to if I have someone else do a calibration?


The labs don’t do any actual calibrating of the mic per se. They measure its response and create a calibration file that can be loaded into a program like REW.




> I suspect you have to have an ANSI traceable mic to test against and controlled conditions for the testing.


I suggest contacting Cross Spectrum or your preferred vendor re their measurement/calibration process.




> Also, could you advise on the receiver mic that I have? Are these not worth the plastic they are molded from? These head units are all now calibrating everything based on these mics. Just curious if they could be used for this purpose if there were a calibration file created for them?


As with the old-styled hardware RTAs, receivers have the calibration for their mics built into the unit itself. As such, one mic naturally wouldn’t work with another receiver. There’s nothing wrong with using a cheap mic, as long as its response irregularities are accounted for. 

It's basic economics. Sure, the manufacturers could include a lab-grade mic for measurement, but I don’t think many people would go for a $2000 upcharge for their $500 receiver... 


Regards,
Wayne


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## fastline (May 7, 2010)

Thanks Wayne. Yes, I understand the calibration process but was not sure why specific inputs and outputs would be required for calibration. I do understand that the mic required phantom power to operate so just trying to piece things together. 

Regarding the receiver mic, what I was try to ask was if there would be any harm in using the mic as long as we were able to calibrate it and create a calibration file? I am not real sure how many frequencies a typical calibration file would have or if there is a Q factor involved in the calibrations in REW. I will chat with a couple labs tomorrow to see what the options are. I am just trying to keep the setup simple and cheap since I probably will not use it much.


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## glaufman (Nov 25, 2007)

If you can get a lab to create a calibration file for it, it should be usable with the calibration file. Exactly how precise that file is will determine how accurate the resultant measurements are. Exactly where the file shows the mic falling off significantly will determine over what range of frequencies the measurements will be meaningful for. At some point the calibration file provides such big corrections that the noise floor masks true measurements.


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

> I am not real sure how many frequencies a typical calibration file would have or if there is a Q factor involved in the calibrations in REW.


To get an idea, you can view our generic calibration files for the Behringer and Dayton mics at our Mic/Meters Downloads Page.




> Regarding the receiver mic, what I was try to ask was if there would be any harm in using the mic as long as we were able to calibrate it and create a calibration file?


Hard to say. Even if you can get it calibrated, it might not even work in the end. For instance, I wanted to use the mic I have with my Audio Control RTA for REW; even had a calibration file for it. But for some reason it wouldn’t work with either a line input or a mic pre-amp input. IOW, sometimes these mics are specific to the hardware and won’t work with other equipmnent like a regular mic would.

Regards,
Wayne


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## fastline (May 7, 2010)

Thanks for the the help. In doing some reading here and other research, I think a generic calibration file coupled with a decent mic should get me close enough for now. I may send my mic in later for calibration. 

I am looking at the Dayton or the CM-140. I am still rather confused on the Dayton though. This is a pro audio mic that requires a preamp to provide phantom power to it. I do understand that. I am just confused as to what other aspects must be adapted to my PC. Does the mic send back more voltage than the PC can handle? 

IE, if I provide a simple power supply for the mic to get power, can I just plug it directly into the PC or is there some reason I must use a preamp? If so, will any mic preamp work or do I have to use s specific one? 



In looking at the cal files for different mics, there is no doubt that the condensers by Dayton and Behringer are flatter and may be more accurate on any given day. For that reason, I am thinking the SPL meters might not be a good selection. Is that accurate?


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

> IE, if I provide a simple power supply for the mic to get power, can I just plug it directly into the PC or is there some reason I must use a preamp? If so, will any mic preamp work or do I have to use s specific one?


Yes, you could use an outboard phantom power supply. Theoretically, you could use a computer’s mic input, as long as it can also be switched to a line input in order to generate a soundcard calibration file.

But then you have the big question of how accurate the computer’s mic pre amp is. I have some confidence in the mic pre amps of USB audio interfaces, since they’re made for recording purposes. Typically only cheapie voice mics are used with computer mic inputs, so how good do their mic pre amps need to be?




> In looking at the cal files for different mics, there is no doubt that the condensers by Dayton and Behringer are flatter and may be more accurate on any given day. For that reason, I am thinking the SPL meters might not be a good selection. Is that accurate?


Not sure I get the question. Are you asking about using the Dayton or Behringer mics vs. an SPL meter, without any calibration files for either?

Regards,
Wayne


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## fastline (May 7, 2010)

I see where you are going Wayne and I tend to agree that the internal sound card of a PC, unless designed for this purpose, could be a major problem. 

I am currently looking at the US-122 as you suggested among a few others. I have heard that the XLR to USB direct converters may not be very linear and could need calibration. 
If I use the US-122, would these also need calibrated before testing? From what I gather from you, the sound card separate from the mic will have it's own response and must be accounted for unless use a recording level sound card that should be relatively flat??


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

Yes, the sound card typically needs to be calibrated, just like the mic. However, you really don't need a calibration file for the Tascam US122. It's ruler flat and down only 0.25 dB @ 20 Hz.

Regards,
Wayne


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