I built two Maelstrom subs with dual passive radiators in 9 cubic foot boxes and I purchased two Velodyne SMS-1 active crossovers for these subs. The instruction manual recommends setting the crossovers at 80 Hz because it is "the THX standard". My main speakers are rated to achieve 32 Hz. I read somewhere that subs should be crossed as low as possible. Since my main speakers are rated at 32 Hz, would it be better to cross around 40 Hz or lower instead of the recommended 80 Hz? I listen to 2-channel music only, no home theater.