I have a problem with a resonance in my room at 35hz, I am sure this frequency is the first harmonic of my room length, as I have to have my speakers at one end of the room and sit at the other there is a peak (or is it referred to as a null?) Either way sounds at 35Hz are louder. I say it is a problem, it can hear it with test tones, but it is not that distinguishable with music, although kick drums do sound good. The problem comes when I want to add a sub woofer in to my system, which I would like to do next year. I can place the sub to minimise the issue but the mains are fixed. I listen to music in source direct mode and the Marantz defaults the main speakers to large so I will still have the problem, which will be exaggerated further by the addition of a sub. Lengthy introduction I know but here is the question, I Bi-Amp the mains, I know could I place a BFD between the AV amp and Power amp and EQ my main speakers to suit the room? I could even roll off the fronts, but is it likely to affect sound quality? How good is the BFD A/D & D/A I know people use them for sub work but would they stand up to being used for Mid Bass duties or is it likely to degrade sound. Any comments or alternative suggestions would be appreciated. Edit I have just had a second thought, if were to get a sub and run it 180° out of phase with the main speakers would this counteract the room nodes?