I've been using a RadioShack SPL meter (C, slow) to calibrate my speakers/amp. The question I have is, should I aim the meter at my rear speakers while doing this? Normally I calibrate by holding the meter in front of my face and pointing up. For the fronts, there is really no difference between doing that and pointing directly at the speakers. For the rears, there IS a difference of several dB. Most noticable is my rear-center. I have it on the floor about 4 feet behind the couch angled up at the back of my head. I know this probably isn't the best position, but I don't anything to put it on back there yet, so it's the best I can do for now. Anyway, there is probably 6dB difference or so in the level, depending on whether I point it at the speaker or hold it in front of me pointing up. How should I calibrate it?