Quote Originally Posted by sba2 View Post
What?s the likelihood that measurements might be contaminated by a mic preamp, like this one that is designed to ?add warmth to condenser microphones? ?
BEHRINGER: MIC100

I?ve been trying to figure out what?s causing some mysterious 2 millisec / 70cm / 28 inch resonances in my measurements. I?m pretty sure they?re not from room reflections.

Is it necessary to have a mic preamp between a condenser mic (ECM8000) and a sound card (Echo Indigo I/O), or would a plain 48-volt phantom power supply be enough ?

http://img819.imageshack.us/img819/2...03millisec.png

http://img444.imageshack.us/img444/4...isecnormal.png
For the mic pre, it depends on whether the "tube warmth" is mere marketing blather, or real. If it's real, the pre will add harmonics that will invalidate your measurements. To find out, download the benchmark software I linked above, and run the tests with your pre in the loop.

Check the soundcard input level (dBu) spec to see if you need the preamp or not.

Your 28" 2nd impulse is a bit harder. Try moving the mic back. Does the impulse change accordingly?