Two chambers each with a port, and a port in between them, but the sub is externally mounted in one, not internally like a band pass. A snail shell is a horn loaded sealed box from what I can tell you, even though the "originators" say it is not.

 

Dave - Pez used to call them a tri-tune or dual chamber reflex when he pumped them out here.

I coined the term ABC for Aperiodic Bi-Chamber (the original name of the enclosure) on TermPro about 8 years ago and now it is a common on-line term.

Interestingly the same Aperiodic Bi-Chamber design is where AP mat technology was born. The original tower was sealed with a resistive mat between the main chamber and a second resonance chamber [img]graemlins/thumb.gif[/img]

[ September 29, 2004, 02:59 PM: Message edited by: Dukk ]

 

Well, as mentioned, the original design was a large bisected sealed tower that had a resistive matte between the two chambers.

Then some super smart dude figured, "Hey man, ported kicks *** over sealed so let's get some pipe!" Unfortunately the "ABC" is a little peaky for in-house use and never got much play from manufacturers. The original sealed unit was gigantic so it never really caught on either.

THe ABC develops two tuned frequencies, the one you tune the vents to, say 30hz (these are better tuned a little lower), and a second 1.9 times (almost an octave) above it, so 57hz in this case.
Biggest mistake people make is similar to bandpass systems - insufficient midbass to keep up with the higher peak.

Size wise - if you have a range of vented volumes for a driver the ABC lives at the top end - think 2.5-3cuft total for a single 12.

I'd give the ABC a 7 on the SQ scale, an 8 on the SPL scale, and an 11 on the 'damn fun box around town' scale [img]graemlins/headbang.gif[/img]

After a few years of us batting the ABC around TermPro, this page was put up: http://www.diysubwoofers.org/prt/dual_chamber.htm

 

yes on the lows, no on the tight.