# input level to low for measurement



## mmichael999 (Oct 27, 2010)

hello guys,

I have the following setup:

MacBook (or Windows Laptop)
M-Audio FastTrack Pro USB Audio Device
M-Audio Studiophile Monitors
Beyerdynamic M01 or Shure Microphone (Low Budget)

I want to do some measurements with room eq wizard. I did the soundcard calibration using a loopback cable from my output dircetly to my input and adjusted the volume - everything worked fine!

After that I want to do the 'check levels' test. I startet adjusting the volume that i hat around 75db at the listening position (SPL Meter).
Then I raised the input level for the microphone - but I can't get enough gain to reach the same level as output (-12 db) the max. value that i have is around -50db..... The mic is working but really silent.

BTW: with this soundcard I can't change volume by software - I have to do this with the hardware knobs on my interface.

please help me to solve this issue....

with kind regards
michael


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

From what I can tell, the Beyerdynamic is a vocal mic and probably is not suitable for frequency response measurements. Measurement mics are typically small element and omnidirectional. On top of that any measurements won’t be accurate unless you have a calibration file for it. The calibration file lets REW “see” the mic as having perfectly flat response.

As to your level problem, it might be that the mic is passive (i.e. requires no phantom power) and as such has a very low signal. If that’s the case, it might not be possible that the USB interface simply can't get enough level from it.

Regards,
Wayne


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## shinksma (Aug 12, 2010)

What Wayne suggests concerning microphone signal level is the likely culprit, IMHO. I assume that your USB card is taking line-level inputs.

SPL meters with built-in microphones output a line-level signal (~1 volt). Regular vocal mikes have a much lower signal level (~1 milli-volts). That's a factor of 1,000, or about 60dB. You'll either need a mike pre-amp to bring the mike-level signals to line-level, or get an SPL meter or other mike that outputs line-level natively.

IMHO, AFAIK, 

shinksma


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