They say that necessity is the mother of invention. Well, I just invented one mother of a subwoofer... In this case, the necessity was to get one of my SVS 25-31CS subs out of a corner and still be able to place both subs on the same side of the room. You see, the corner loading with two subs side by side was introducing some nasty room modes and some serious humps in the lower frequencies. In moving the subs around, I discovered, with the expertise and encouragement of Mike Knapp and another chum with just as accute hearing, Ken Gunlock, that my low bass was overpowering my mid-bass and midrange frequencies and totally muddying up my soundstage. This was much less of a problem with movies than with music, however, with the recent upgrade to some beautiful sounding B&W Nautilus 804 main speakers, my music reproduction has become far more critical. I've been kicking around the idea of stacking two SVS subs for some time, though not for this reason. My original idea was to use TWO two-sub stacks in a larger theater room so one could get four subs in a room without some of the placement problems that goes with such a configuration. I decided to make a practical application out of my idea with my two subs to see if it would solve the placement problem I had in my room. This is what turned out... Here's a closer look at the joining of the two subs... The resulting sound, I am very pleased to report, solved my problem. My bass cleaned up nicely and I didn't lose any impact on movie soundtracks. Music sounds way better. I don't know if I can recommend this application to everyone, but for the record, my wife prefers the "tower of power" over putting one sub on either side of the mains.