@HopefulFred - Thanks for that document. It was a good read. Though I will need to read through it a couple times to soak it in. I visited the REW forum yesterday and got signed up. I installed the freeware and late last night I was able to calibrate before getting some rest. Everything is setup still so hopefully I can get some information together this evening after work. Though I have a few questions for the REW users over forum. The output would stay solid at -12db, and in order to match the return I had to turn my microphone and even the source really loud. Do so resulted in clipping during the sweep test... The tutorial I watched said to stay within 6db. Other than ignoring that advice I didn't find a way last night to correct the mic clip. Yes the sweep was really, really loud and the mic was clipping appropriately. Setup is a Mac, FireWire connected to personus firestudio, using a sterling st55 condenser.