I'm still struggling with adapting to a new home. The main HT room is almost a cube. It is 17.5 wide by 19 deep, with a flat ceiling that is a shade over 18 high. The east wall (17.5) consists of a stone fireplace flanked by built-in bookcases that extend to the sidewalls. A Pioneer 50" plasma is being mounted above the fireplace. Paradigm Reference Series Studio 60 loudspeakers will be in front of the bookcases and act as the mains. I'm still struggling with what to do about the center, but that's a whole 'nother thread (leaning towards using a phantom center right now, as my CC450 and anything comparable just won't fit). The room is open to the rest of the house at the northwest corner (left/back). The south wall is mostly windows, but with full length, heavy draperies that are usually closed when the HT is in use. All other walls are drywall. In wall speakers on the west wall are used for the rear channels, with wall-mounted dipoles on the north and south walls for sides. The floor is berber carpet over wood subfloor, with a basement below. My sub right now is an M&K V75 Mk II, and I've been pretty happy with it in my previous home. I'm not getting decent sound in this room, however. I think the sub may simply be inadequate for the room, but I am willing to play with placement. The basement is unfinished, so I can run a hidden cable to just about any spot. Of course, I may also take this opportunity to upgrade my sub, and put the M&K in bedroom. I'm thinking of running a cable and placing the sub in the right rear (southwest) corner. This is exactly opposite where it is now (front left). I've never run a sub BEHIND my listening position, however. What do you think? Anyone else running a sub behind the listening position? Do I need a larger sub? Is it a room size/harmonics problem?