Hi All, I've recently moved house and want to improve my sound system. The room is 18' wide, and 13'5" deep and 8' high, with a wooden floor, with a cavity underneath into the foundations, think it's about 2' deep, but I haven't had floor up yet. The house is detached. There is no room for sub woofers on the front wall (due to doors, screen and front speakers), but there is plenty of room on the back wall. The back wall is an exterior wall, plastered breeze block on the inside then cavity thermal insulation, then red brick on the outside, and is approx 11" thick. Behind this wall is about 5' then the neighbors wall (same construction as mine) which runs parallel to mine for 2', then cuts away and runs parallel to mine at about 11' away for the rest of the room. Now ideally what I want is to play movies at -10dB from reference (Dolby D and DTS), going right down to around 12-14Hz (or as close as I can get). I also wanted two subs (currently with a single sub, as I can't sit still and by moving about, due to the (close) distance I'm sat from sub, the pressure varies by a noticeable amount and then I'm aware where the sound is coming from and the whole experience of being there is broken). So I was thinking two SVS PC13-Ultra. Now would those subs completely overpower the room and become unmanageable? Would a SVS PC13-Ultra and a SVS PC12-NSD work well together, to produce something a little bit more manageable, or is mixing the subs like this just asking for problems? I'm happy I can take anything above 100Hz right down to under 30dB(A) in my neighbors house without issue, and I'm not planning on having it as high as -10dB very late at night, so I'm happy that this part is acceptable. I'm thinking of getting 2 front speakers that can go down to 32-38Hz @-3dB and have the cross over at 40Hz to 50Hz, which will be 11' away from the back wall, and the subs placed either in the back two corners or 1' to 2' from the back wall (depending on room nodes etc). This means there is a maximum of 111dB(C) coming through the sub woofers (115dB LFE + base from other channels -10dB from ref) at 5'. Now for the bottom two octaves (10-40Hz), I'm not convinced the walls are going to do much in the way of knocking out the bass getting to next door, to a level of 30dB(A), which I'd imagine is a reasonable level (for waking hours). So firstly given I've got a theoretical maximum of 111dB(C) (at 5') (roughly 79dB(A) @40Hz, 67dB(A) @20Hz) through the subs, what is the chance of this being all in the 10-40Hz range and for a long time (say 4seconds per 5 minutes, or 3 seconds continually)? Is there anything I can realistically do to limit what the neighbors hear/feel without destroying the quality in the room, such as placing bass reflectors; bass traps in the room/under the floor; placing the subs right next to the sofa; turning them down by as much as 20dB; put 2' of glass fibre backed with gypsum board and 4' high along the outside of the wall (and risk looking mental); or build by own closed passive subs in the sub-floor? Any help or advice would be much appreciated.