MM-1 : Inaccurate calibration

I compared this to a Sonarworx microphone using Sound ID reference to calibrate speakers in an acoustically treated room. I had to very carefully enter the printed custom calibration graph as a list to make a calibration file for Sonarworx. The graph claims the mic is flat within 2dB for 85% of the spectrum.

However I got quite different results between the two mics. The T Bone produced quite a different curve above 2kHz which gave an audible difference. Sonarworx themselves confirmed that the cal file was fine so I can only conclude that does not match the microphone. Perhaps there was a mixup at the factory, or the mic's performance has degraded since I bought it in 2018.

The mic does sound flat when used for recording.