i dunno, Pete doesnt really tell you much about the design, i asked him and this is what i got....
"It's a mass-loading flare-ported enclosure that, in part, takes advantage of the inner-port resonance to boost the low end. Still a ported box by the virtue of the "air spring" but with certain proprietery advantages. You can expect an F3 of about 25Hz with this thing and, if you give it enough power, somewhat of a mayhem at around 35Hz which is where the box ripples at. From there, it stays pretty flat 'till about 150Hz which is where the quarter-wave anamolies begin to kick in."