Help with mic calibration effort...

[John Mulcahy]

I don't see any change of shape when adding an offset to the REF mic measurement. Remember to use "Add offset to data" after you move it.

All the measurements have abrupt high frequency cut offs, the REF cuts off at 10 kHz and the other two at 13 kHz. That's probably due to failing to capture the end of the sweep due to replay latency, use the acoustic timing reference to fix that.

 

[John Mulcahy]

Changing the gain of one channel in an alignment sum isn't the same as adding an SPL offset to a measurement. One of the measurements rolls off at 10 kHz, the other at 13 kHz, so their sum is going to look odd if you are changing the contribution of the one that stops at 10 kHz.

 

[John Mulcahy]

If you divide magnitudes, there will not be any phase.

 

[John Mulcahy]

The chances of you getting meaningful phase compensation data are close to zero. You definitely cannot do it with measurements at the listening position, that is also true of the magnitude compensation. It is hard to do it even with carefully collected nearfield measurements from a suitably wideband source far from boundaries or in a test chamber. If you feel you must have phase data for the corrections you can create a minimum phase response from the compensation file, but if the compensations are invalid due to the measurement conditions the phase data will be worse than useless. Mics have negligible phase contributions anyway, other than small shifts at their lower and upper roll-offs and around any resonances.

 

[John Mulcahy]

You mean the file you attached in the first post? Those measurements were incomplete (stimulus not fully captured), all the measurements look to have gone through resampling (was the sample rate for the interface in Audio Midi Setup the same as the rate in REW) and they have large close reflections, the L mic and R mic particularly. Perhaps the reflections are partly from whatever you are using to hold the mics. Mics differ little in their LF response, you may get better measurements by placing the mic near field to a tweeter.