...Reading briefly I think I saw a sentence that suggested that I place additional subs in room nulls. Is that correct? Could I walk around with a mike and choose locations based on where I find nulls?
Yes, absolutely, you can and should set up four subs in what I call "Progressive Null Points." I presume the definition of a NP is where modal effects are minimal. So far it's worked in every room in which I tried it.
Bob Carver used to provide similar instructions for one sub.
You don't employ the main speakers during this setup. Start with one sub located at the sweet spot. Play tones in the range you desire to employ the subs. Check every potential sub location for the smoothest bass, which in my experience will be the location with the least overall output, least modal effects. Once you find the NP you might be very surprised that moving the mic even 4" off the NP causes serious increase in modal peaks. The edge to the NP is much more abrupt that you might suspect.
What you are doing is a mirror image of testing with a mic at the sweet spot while moving the sub to every potential location.
Set the second sub at the first null point and repeat the test playing bass tones on both subs (sweet spot and first null point). Continue adding 3rd sub to the next null point, then finally (playing all subs each time you add one) find the 4th null point and move the sweet spot sub to that point.
Now invert the polarity of each sub separately till you find the smoothest FR (this test will be obvious). Set global phase to 90 degrees and you're done except for level, crossover pole, and minor global EQ.
You should have only minor mode effects in corners, and very smooth bass everywhere else in the room.
Hope it works!
Love the speakers BTW!
