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Converting a 0 Degree Calibration File to a 90 Degree File


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I bought a UMIK-1 from MiniDSP. It only came with a 0 degree calibration file, but I needed a 90 degree calibration file. So, I wrote this utility to approximate a 90 degree calibration file from my 0 degree file.

 

This utility will compute the difference between two microphone calibration files and use that to offset a third file.

 

I have included average 0 and 90 degree files for 10 UMIK-1s measured by Cross Spectrum Labs. It's interesting to note that there is a wide degree of variation between samples. Also, the MiniDSP measurement is quite different than the Cross Spectrum measurements. You can check out the reference data in the included Excel file.

 

I don't really know whose measurements are correct, or if using this micdelta utility will give you good results, but you are welcome to use it or do whatever you like with the code.

 

Alternately, the average Cross Spectrum measurements may be useful to you as generic calibration files.

 

I also included my individual calibration file from MiniDSP, as an example. You would want to replace it with yours.

 

This utility will also work for other brands of microphones, if you have reference 0 and 90 degree data files from one or more microphones of the same brand.

 

Example usage:

micdelta.exe umik1_avg_0.txt umik1_avg_90.txt umik1_ser7003955_0.txt umik1_ser7003955_gen_90.txt

 

Running this command will generate a 90 degree file (umik1_ser7003955_gen_90.txt) from my 0 degree file provided by MiniDSP (umik1_ser7003955_0.txt).

 

Thanks to Flavio from Dirac for providing the reference UMIK-1 calibration files!

micdelta.zip

ref_0.gif

ref_90.gif

results.gif

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The 0 to 90 degree deltas from Cross Spectrum Labs are incredibly consistent, so it appears that this technique of applying deltas has merit.

 

Excellent Robert,

 

I think it can be very useful and we thank you for sharing it,

Flavio

Warning: My posts may be biased even if in good faith, I work for Dirac Research :-)

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Excellent Robert,

 

I think it can be very useful and we thank you for sharing it,

Flavio

Actually, given the consistency of the deltas for each microphone, it appears that even using a single set of measurements could give good results for other brands.

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Actually, given the consistency of the deltas for each microphone, it appears that even using a single set of measurements could give good results for other brands.

 

Well... for other brands both the vertical and horizontal actual calibration files would be needed to determine the delta, and also we would need a number of actual calibration files to determine the consistency between different units of the same model (I only have ten from miniDSP mics)

 

:) Flavio

Warning: My posts may be biased even if in good faith, I work for Dirac Research :-)

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Well... for other brands both the vertical and horizontal actual calibration files would be needed to determine the delta, and also we would need a number of actual calibration files to determine the consistency between different units of the same model (I only have ten from miniDSP mics)

 

:) Flavio

Yes, that would be assuming that other brands are as consistent as UMIK-1s in terms of the consistency of deltas between 0 and 90 degrees. My guess is that there is nothing magic about UMIK-1s here, and that this will apply to all brands, but without supporting data, it's just a guess.

 

It would probably still be important to use deltas from the same type of microphone, though, even if one sample is sufficient.

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Yes Robert,

 

also as you said it is not intended to replace the purchase of an UMIK-1 with an actual 90° vertical calibration file from Cross Spectrum Labs (which is certainly worth 20 dollars) but as a useful solution for those who already have an UMIK-1 with 0° calibration only.

 

:) Flavio

Warning: My posts may be biased even if in good faith, I work for Dirac Research :-)

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mmm... may be some instructions on running "micdelta" with Win7 could be useful:

 

- The 0° calibration file of your UMIK-1 should be copied inside the micdelta folder together with the other files

 

- Press and hold Shift and right click on the micdelta folder to open the command prompt at that location and click on Open Command Window Here

 

- Enter the following string replacing umik1_serXXXXXX.txt with the name of your calibration file:

micdelta.exe umik1_avg_0.txt umik1_avg_90.txt umik1_serXXXXXX.txt umik1_serXXXXXX_90.txt

 

- Enter

 

DONE (hopefully) :)

Flavio

Warning: My posts may be biased even if in good faith, I work for Dirac Research :-)

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