How did you gain this information?
Yeah, that's a good question. At the moment, just by listening, using a software sine wave generator, optical cable to an Ultradac and on out. I need to get an spl gauge, I suppose, since the subjective perception is hard to estimate in db's! However, there is no mistaking how the sound rises as it approaches 65 Hz.
Also, by calculation! The room is 18' x 17.5' x 8'-9' (height); the ceiling is not parallel to the ground, however, so vertical standing waves are less problematic. There is a fundamental resonance centered at 32 Hz, but my speakers don't go down that low so I cannot hear how bad that is (except when helicopters fly overhead, etc.).
Regarding room treatment, that's the other direction. Since I'm renting, I don't feel like spending a lot of $$ in that direction. I got a recommendation to use quarter-wavelength pipes (e.g. sono tubes) sealed on one end. In this case, I'm looking at 4.5' long tubes, lying down on the floor, or hanging along the ceiling. Can you feel the WAF?
I am considering adding a pair of subwoofers, which involves getting a passive pair, a crossover and an amp if I want to do it right. In that instance, I could use the notch filter(s) on the subwoofers, hand things over around 80 Hz to the rest of the system and be done with it. I'll have to do something about that 32 Hz resonance, then.
Here is something that I wish could work--it's so simple!
http://www.diysubwoofers.org/bnd/notchfil.htmI shudder at the thought of putting that right before the Ultra 550's inputs, though...
