Hey, Odeon,
What do think of this subwoofer design I've been working on for a while.
Sorry the pic is drawn up in Paint, but it just struck me that your comments would be fun.
All the black is solid MDF or filled crevaces loaded with expanding urethane foam.
The cyan color is the sealed compression chamber. It is tapered on all four sides like a pyramid, to remove any possibility of standing waves within the chamber, since there are no constrained parallel surfaces. Shaving the oustide dimensions also completes the expansion of the port/horn to maintain something close to an hyperbolic curve in the cross sectional area.
The magenta color is the tuned chamber, which makes this a fourth order enclosure. There are also no parallels. It is tuned by a simple port, typically, but my design is tuned by a small hyperbolic expansion, folded over itself similar to a horn (the white area).
The green color is actually a sealed isobaric chamber, which acts to couple the two (drivers) moving masses, but in a buffered manner as opposed to directly bolting the drivers face to face as with typical isobaric designs. The two driver magnets are actually solidly connected by an MDF spacer to reinforce the non-moving structure and keep it as inert, non-resonant and rigid as possible. The isobaric chamber is a very solid, sealed unit with the driver diaphragms firing in opposite directions, but phased so that the diaphragms move as "one single piston".
The red arrows represent the dual airpath and the expansion of the port/horn. The expanding port should have a much broader range of resonance than a typical tube type port.
It's almost done in a half size, using six inch drivers, for a mock-up test.
BTW, I haven't invented anything. All these ideas were first explored by Bell Labs, Westinghouse and a few others in the 1920s, 30s and 40s. I have just combined the ideas into one, no holds barred, enclosure.
Oops. I tried to attach a bitmap. I'll try again.
"Is she gone yet?"