Here is what I've been thinking. I need approximately 900 liters' worth of space for my 4-driver subwoofer. Initially, I planned to build it as a base for my center channel, in 4 220L boxes. Now I realize 900 liters is the approximate size of a *huge* refrigerator. It's just *too* big. I don't want to lose low frequency response, though. An IB is out of the question, too (the drivers drop off too fast on an IB enclosure). How about a sofa riser, then? If I built it, I could have a 900l enclosure with zero problems whatsoever. The questions I have, though, are... 1) Should the drivers be firing frontwards, backwards, sideways, or straight up to the sofa? 2) What about the ports? 3) How would sound quality be affected? 4) Do you think I could have any other options for building such a huge sub enclosure? Thank you very much for your help! Javier.