"The test mic will give the software roll off points I assume?" One uses the mic with pink noise (there are free downloads as well as test discs). I usually measure with the subs turned off. In a room bass frequencies sum. So one does not want to have the main speakers producing the same frequencies as the sub and causing a bass bump at certain frequencies. So note where the mains start to drop off and set the Rel accordingly (I currently have a pair of Rel S/812s in the main system) and then test again and get it as even as possible without peaks and dips in the lower frequencies. I also use room treatments.