# Creating Microphone Calibration File



## shangara (Oct 18, 2010)

I have access to a calibrated Earthworks M30 microphone and thought I'd try to create a calibration file for my ECM8000 by averaging 8 test sweeps for each microphone then using the arithmetic function of the 'All SPL' graph area to subtract the one from the other and so end up with a difference curve which would be the calibration file for the ECM8000. I used the A/B function as the sweep magnitudes are in dB (logarithmic) and exported the resulting graph as a text file. I then used this as my mic cal file and it seems to work perfectly...

Is it possible to reduce the number of points when exporting a text file from a measurement as the resulting cal file is very large (over 50,000 points).


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## chris319 (Dec 16, 2008)

Are you setting your impulse response window to eliminate room reflections?


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## shangara (Oct 18, 2010)

I can't set the window too narrow as I need all the information in the low frequency range.
This is not a problem as both sets of measurements are made under identical conditions, only the mic is changed. The unsmoothed difference curve is reasonably useable, but has some anomolies. I found that the best results were obtained when using 1/3 octave smoothing on the measurement graphs before making the difference file.


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## JohnM (Apr 11, 2006)

shangara said:


> Is it possible to reduce the number of points when exporting a text file from a measurement as the resulting cal file is very large (over 50,000 points).


No, but export at fractional octave intervals is on the list to be added at some point.


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## shangara (Oct 18, 2010)

JohnM said:


> No, but export at fractional octave intervals is on the list to be added at some point.


Fantastic - and thanks for a superb package !!


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