Ahhh....I think I follow you now. The 2 outside chambers are internally ported into the center chamber which in turn, is ported to the front baffle. This would create a primary load at 60hz on the two drivers, but I'm curious how that interacts with the secondary loading at 34Hz. I believe KEF and Mirage both use different size ports in their systems, but that is with a common chamber. Interesting.
Looks like here is the link you used (thanks, Google):
http://www.diysubwoofers.org/prt/dual_chamber.htm