[andrebrito]

Has anyone else actually tried an ECM8000 and tested or calibrated it?

I have used this mic. It works ok and it is usable for most applications apart from environmental acoustics where you need to have an accurate value of sound pressure level (you really need to know that for instance the value of Ln at night is 44.0 dB and not 46.0 dB).

For room acoustics in terms of room modes, rt60 etc.. is in my opinion enough... unless you are a bit paranoid and pretend to have a completely flat room !