I have a rec-room that is 13'x21'x7'. There is no way to use an adjacent room as the IB, so I'm wondering if I could just make a really big enclosure at the screen end of the room. So as an example, 1.5' depth x 13' x 7' would give me 136.5 cubic feet or about 3900 litres. From what I've read, you want VAS x 10 for an IB. So a Tumult would need 160x10= 1600 litres. Could I then mount 2 Tumults in this space and get the full benefit of an IB? Will this give me 115db+ from say 15hz and up? I want the best sound quality and high SPL, is the Tumult the best IB solution here?