First make sure that it's NOT the equipment. Using a test CD monitor the AC voltage at different frequencies. If that's OK check the speakers. This is a little tougher. Best would be outside if you have long enough cable, otherwise in the largest room. Using only one speaker and an SPL meter monitor the level at different frequencies. The meter should be very close to the speaker. Also check with Avalon about any impedance anomolies at the offending frequencies. Also the resonant frequency of the speaker / spike / floor combination could be an issue. Get the exact measurements for the room and calculate areas that would be likely to give you a problem. If the room measurements are OK than it's not the room. Bad floors are a possibility too. Contact me back in a few days after you've tried some of my suggestions. By the way, a good SPL meter and all purpose electrical meter are indespensible. Also get all of the cheap test discs that you can. You never know when one will come in handy.
Room Acoustics
Suggestions for this annoying problem appreciated.I get an annoying room resonance in the low mid bass that just excites the hell out of the room in spite of speaker placement, different amps, and corner treatments( 4 corners with ASC super 16's to the ceiling), curtains over sidewall windows etc. Speakers are Eidolons, room is 15wX22dX9h. Short shag carpet, speakers on apex couplers. Sound is 99% stunning with that occasional Dave Holland bass note that just won't quit. I think it's possibly the floor, pier and beam over a finished rec room in basement. I'm considering putting the Edolons on granite and maybe having someone professionally check the room acoustics. Is this related in any way to the downfiring port of the Eidolon?. Thoughts appreciated including any suggestions as to someone coming out to test the room. Thanx in advance.