Having read the "sub behind sofa" thread, thought I would ask this question. In my house the staircase comes down into the lounge, (which is where I have my AV kit). The space under the stairs is just the right size for a PB1-ISD, but I'm unsure whether having a downward firing sub in an enclosed space would cause any problems. My XLS is currently part way under and doesn't behave any differently there than in a more open area but obviously that is front firing. I'm not too worried about boom as I have just acquired a BFD, which has tamed a nasty room mode quite nicely. Now I'm hearing cleaner bass but I want a bit more of it. (Must also stop reading these threads ) I'm about to send my room details over to SVS and will ask them the same question but I'm also interested if anyone here has used a similar type of semi-enclosed space for their down-firing sub.