# Microphone does not work with REW



## knacknack (Sep 17, 2013)

Hello Forum,

acutally i want to improve my speaker system by a pair of miniDSP. Because of the possability to import REW-Files into the miniDSP-Software i want to use REW for measuring and adjusting the frequency response. I am using an aureon 7.1 usb-soundcard combined with the 5.01 beta 17 REW Version, Windows XP and miniDSP 21-Advanced Plugin.

In the properties i select my Aureon-Soundcard as Input and Output. The Output works fine, but if i want to take a measurement, i always get the same headroom (around -40dB), no matter how loud the test sweap is. I already tried to plug the microphone into the line-in and the normal microphone inputs, but it doesn't help, i don't get a measurement. Any ideas what can solve the problem?


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## JohnM (Apr 11, 2006)

Are you able to record from the mic using Windows Sound Recorder or Audacity or similar?


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## knacknack (Sep 17, 2013)

Yes, i can record from my mic using audacity.

Edit: Actually i got finally some records with REW, but they don't look like that they come from a speaker. Sadly i have to work under Windows XP so the sound settings are quite complicated and confusing to me. Therefore i am working with a aureon 7.1 usb soundcard i can select different input channels. I am able to select the Mikrophone, the Line-In and the Wave (whatever this is ?). 

The red line got drawn if i select "Mikrophone".
The blue line if i select "Line-In" and
The green line if i select "Wave" (looks like the measurement from a soundcard...)

The mikrophone was actually plugged into the Line-In input.

I did the same again but this time i plugged the microphone in the "microphone-input" from my sound-card. Same colors and same input-selection as on the first picture. It still does not look like a valid frequency response 

Finally after pluggin the microphone in the second microphone input (yea, two microphone inputs on one soundcard...) i got this from REW, from all SPLs it looks the best to me, but the strong drop to the high frequencies can be caused by my microphone but i am not sure...


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## JohnM (Apr 11, 2006)

You definitely should not select WAVE, since that is the output signal - selecting WAVE feeds the output straight back into the input through an internal loopback.

If your mic is a condenser type it will need some power to operate, which would be supplied by a mic input, so the right combination is most likely to plug it into the microphone input and select that input in REW. You also need to check the Windows volume control for the output to make sure that if the microphone connection appears in the list of output volume controls you mute it, that prevents another loopback path being created.

A bigger issue is that you don't know what the mic's own frequency response looks like, so you won't be able to tell what part of your measurements is due to your room and speakers and what part is due to your mic. The ideal is to have a calibrated mic, as the easiest one to get set up is the UMIK-1 from MiniDSP as it is a USB mic and the volume control handling is much simpler, and REW V5.01 beta versions will automatically detect a UMIK-1 and ask if you want to use it for measurement.


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## knacknack (Sep 17, 2013)

Thank you very much for your reply, if i can get more comfort with the UMIK-1 i will go for it. Do i i only need a free usb-port no external power supply? Is there a calibration file coming with the umik-1? Or is the frequency response from the mic so smooth without any calibration file?

Edit: I looked around on the internet for opinions about the UMIK-1 and i read that the calibration is not made for every single mic but for the majority therefore it is not so exact...


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## JohnM (Apr 11, 2006)

That is incorrect, the mics are all individually calibrated but you can also have them independently calibrated by Herb at Cross-Spectrum. There is no need for an external power supply.


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## knacknack (Sep 17, 2013)

So i will get a nearly perfectly smooth frequency response with the calibration file on the UMIK-1?


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## JohnM (Apr 11, 2006)

You will get an accurate picture of the response of the system you are measuring, without influence from the mic's own response.


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