Bob has been helping me behind the scenes, and here is part of one of his pms:
[qoute]Anyway, you have room modes at:
24, 48, 72 hz
51, 102 hz
79 hz Basically don't have your ear height at about 1/2 this dimension, this would create a null around 80hz. Not a good spot for a nulll with the crossover at 80hz.
Now as I said real world measurments are not as perfect as calculated. Now using your seating measurement you have basically placed yourself in a null at 48 and 51 Hz. Which between the 1/6 octave measurment and real world fudge factor I bet is the 56hz on your graph. You have a double whammy there causing that nice dip.
Move your seat forward (only the mic for now) 1.5 feet and move the sub about 62" from the side wall and then move it 44" into the room. Now take your measurements." [/quote]
Well Bob, I did as you suggested and moved my main (only using dedicated sub for these tests) sub 66" from the side walls (BTW this places it almost dead center in the middle of my stage, and then moved it ~44" out from the front wall (I will attach a pic in a minute so you can see physically where it is). Since I wasn't sure if the 44" was to the front of the sub, or driver or middle of sub enclosure, I placed it ~44" to where the magnet on the driver probably is. The front of the sub is 48" to the wall and the middle of the enclosure is 40" if that helps any.
Well the response curve (green) is much better and the 56Hz null is much improved and there is a slight dip now at 50Hz. Overall though this is better. Now the problem is....the sub can't stay there (see next pic...it's exactly where the center channel will go), and the listening position is fixed at slightly 1' back from where I moved the mic (the mic in this measurement was 6' from the back wall, and 3' from the side wall). But I think we are just trying to determine the IDEAL sub location and understand my room modes. Based on Bob's curve (green one) I should be able to flatten out at about 80dB from 25Hz-111Hz using the BFD no?
I have been measuring from what will be my music listening postion (rear row), however, my main movie watching location will be on the front row and I have not taken any measurements there....should I?