I have a Klipsch KSW-12 downward firing sub. I'm very happy with it except that when running low frequency sweeps on AVIA I get low spl meter readings at a couple of places as the frequency dips. I've got my receiver crossover set at 80hz, all speakers small (bookshelf Energys), and the crossover on the sub set at it's max. I have tried switching the phase switch on the back of the sub with no real improvement. I like my HT sound overall, but am contemplating experimenting with sub placement to see if I can get rid of those "dead spots." My HT is arranged corner to corner, with the rptv in one corner. The sub is now next to the right side of the tv takes up all the room between the tv and the wall, with it's front lined up with the front of the tv so the port in the back is at a 45 degree angle to the wall. Since it's downward firing, I'm wondering if it's going to be badly muffled if I try putting it in the corner behind the tv? I don't really have very many options as far as placing the sub. My last experiment with placing it ended up giving the best and flattest response with the sub in the dining area adjacent to my HT room, not a good placement. I do have an unused brick-lined fireplace in the right wall and have given some thought to placing the sub there, lol.