To line them up exactly I had to add 2.8 dB to the calculated cuve.From this I can be fairly sure the method I’m about to use with the Behringer ECM-8000 will give me a usable calibration curve.For this I measured the ECM-8000 the same way, through the Behringer mixer and USB sound card. Turns out division (uncalibrated / calibrated) gave me the curve back.I used the raw response (no smoothing or gating) data as the source of the calculation, then smothed to 20 for visibility, phase displayed just to show mostly flat.This is superimposed on the actual calibration curve supplied by miniDSP. If I can generate something resembling the calibration curve by comparing measurements with and without the calibration file applied, I should be in the right ballpark.Here are the homimpulse measurements with and without the calibration file, smoothed to 5 per octave to make the differences easier to see:Here is the “no calibration” measurement, divided by calibrated – using the Holmimpulse frequency domain manipulation functions. I’m not actually concerned too about the response of the speakers now, just that the measurements remained consistant between holmimpulse runs, which they did.As a sanity test I’ll calibrate the Microphone against itself.
With the UMIK-1 curve a bit different. The file exported is 1997 lines compared to the 560 lines of the UMIK-1 calibration file, so possibly overly detailed compared to the source data – but using this calibration file with Holmimpulse, I do a frequency response sweep and compare against that done with the UMIK-1:And the calibrated/uncalibrated curves are quite close. It has been offset by -6.5 to line up with 0dB, and the UMIK-1 calibration file and generic ecm-8000 calibration file are also shown (blue and green).Smoothed to 20, although the imported calibration curves obviously are even smoother.With Holmimpulse I can export as a calibration file. They are quite close.Calculated ECM-8000 calibration curve (red). The ECM8000 measurement has also been reduced by 6dB to line up closely with the UMIK measurement for comparison.
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