"I am not sure I have emphasized enough just how much power this sub actually has. In the 30-80 hz range it will bring beyond commercial cinema level of impact to just about any home theatre size space. And unlike your local cinema, it does this without giving up on below 30 hz output..."
"The S21ipals are amazing beasts. The fact that something so small (24" cube) can bring single digit ULF and play complex bass so transparently still boggles my mind. The current delivered by the SpeakerPower amps to 21" ipal drivers is hard to believe.
I have 4 corner loaded S21ipals in ~5200 cu ft driven by a pair of SP-2 8K rack amps and the only limitations are how much single digit bass will knock my projector out of alignment and how much current can my electrical system provide."