I use a Lexicon Ionix U22 interface that provides the 48v phantom power and gain. That feeds a laptop with either REW or ARTA or whatever other measuring software I might need. I also use the interface for recording.Do you feed the ECM8000 into a laptop and, if so, how do you do that? I have one with an XLR out. Also, do you know how much changed with the calibration? Mine isn't and I don't have a serial number.
As to calibration, I did that myself against a calibrated Earthworks microphone, and derived the curve which REW or ARTA use. Somewhat tedious to do but I thought necessary for my application which was to equalise my speakers pseudo-anechoically to +-1dB. The mic is OK uncalibrated for checking in-room responses as calibration errors of a couple of dBs are of little consequence, but those are of the same order as I was trying to correct so thought I'd do it properly, and learn something at the same time.
S