To begin with, I am not really a subwoofer tweaker. I had set my sub a year ago with the Avia disc to match my other channels (albeit a tad fatter), and it has stayed there. Now recently I got the Behinger Feedback Destyroyer Pro from a local shop and I have tried putting it in my system as a sub filter. Here are my issues. Please tell me if I have done anything wrong, or if I am missing something. - started at the same volume I use as my listening level while watching movies (-10 dB) - using a Stereophile stereo test disc (having my speakers set to small and the sub crossover at 80), I ran through low frequency tests - major dip (-10 dB or more) at 63Hz...the rest kinda flat - i tried adding gain to smooth the dip, but even +16 did nothing (I am assuming some room cancelation) - used negative gain across the rest of the spectrum to flatten the response to the 63Hz level - because the mains cross at 80Hz, the mains still produce a higher level of 80Hz, than the sub at 63Hz, so I dropped the level of all 5 main channels so that the 80Hz signal is the same volume as the 63Hz tone - low frequency test tones are now relatively flat from 80 to 20 - i need to raise the main volume now to approximate the levels I was listening to before - i have only tried music in stereo - i have not watched a movie yet or listened to multichannel music (SACD or DVD-A) - using the Avia disc once again, the levels are flat across all 5.1 So, have I done anything wrong? I wish I wouldn't have had to lower every frequency except 63, and just left it as it was, but I couldn't get it roughly flat. Is there some problem in doing this that I can't see? When I put a movie on, THX will be engaged and the speakers will cross again at 80Hz. Should this work properly now as well? What will happen when I put in an SACD? My player has no bass management for SA. My mains will play as large, and the sub will get whatever is directed to the LFE? Is there a problem potentially with this scenario? I am assuming that running DVD-A with bass management should not be an issue. I would assume it would work in roughly the same way as the THX crossover. Essentially, I am concerned that my settings might inadvertently damage the sub. If that isn't the case, does anything glaringly sound wrong with what I have done? I think that if I was watching at my reference level, and I hit the by-pass button, the sub would be way too loud (perhaps damagingly loud). I will make sure I don't engage the bypass. Anything else? Thanks.