Test of 12" Mic and Earthworks M23 Using SIA and Yamaha Mixer

We used the Earthworks M23 measurement microphone, which conforms closely to published specifications,   as a reference because we don't have an SPL calibration standard.

Test of 12" microphone using setup A, without open cell foam in plastic ear canal.

(see schematic)

Test of 12" microphone using setup A, with open cell foam in plastic ear canal.
Test of 12" microphone using setup B, with open cell foam in plastic ear canal.
Test same as above except mic was replaced with Earthworks M23 microphone.
Test of 12" microphone using setup C, with open cell foam in plastic ear canal.
The 12" mic and the M23 were placed about a half inch apart to record hand claps. see (Test Setup D)

Hand claps were recorded with 12" mic channel gain 44db lower (pad completely CCW) than the M23 channel (pad completely CW). Then the relative loudness was measured and the 12" mic channel loudness was 11.79 db lower than the M23 channel. The 12" mic wave file was adjusted +11.79db to achieve the same loudness in each channel.
A weighted noise of both microphones with the M23 channel adjusted by +32.21db to achieve the same amplitude of the hand claps. The noise from the M23 in the 8khz band is about 22db higher than the noise of the 12" mic.

Although somewhat removed by A weighting, there is a small amount of acoustic background in both channels in the region below 200hz.
IM Distortion of 12" microphone and test equipment using setup C, with open cell foam in plastic ear canal. Test tones are 200hz and 300hz. Picket at 100hz down 60db, 700hz and 800hz down 66db.

It appears that IM of driver and mic is about same as reference. (6db increase)
IM Distortion of reference channel in test equipment using setup C. Test tones are 200hz and 300hz. Picket at 100hz down 66db, 700hz and 800hz down 72db.
Total harmonic  Distortion of 12" microphone and test equipment using setup C, with open cell foam in plastic ear canal.

THD measured with DSSF5E.