My version of '4+4' configuration uses inexpensive 1/2 cu ft rectangular Dayton cabinets -- which have some high frequency resonanant sound when tapped.
Use of 'quasi aperiodic' loading is expected to reduce back-pressure on drivers and the cabinet walls - for less resonance excitation. IMO, this approach can be made to work with some custom response contouring.
Rectangular Dayton cabinet was chosen over Dayton curved cabinet because have to mount four drivers on the back of the cabinet.
BTW, I have a pair of 1 cu ft curved Dayton cabinets originally used in array of four Audience A3 drivers, but feel that these cabinets are just too big to fit in allotted room space, and size is a WAF consideration (with TV/small HT/stereo, and computer room speakers).
Optimism: My Monitor Audio 'Silver S1' cabinets have even a worse audible resonance than the rectangular Dayton 1/2 cu ft cabs when tapped - yet these MA speakers still manage to sound good. Also, VMPS speakers use interior borosilicate coatings (Acousti-coat) on MDF for apparently good results.
Yes, there are better enclosures.
Before getting the Dayton cabinets, I did pursue better alternatives including something like Audience's great 15" wide, closed, curved cabinets - now the superior Clairaudient cabinets are made using CNC machining (I understand).
Also initially considered an open-baffle configuration but the physical size is a problem -- if all else fails, may go back and pursue a better cabinet/more heroic bracing and so forth. For an OB, could use light weight constrained-layer materials (ref 1998 Audio Express article on 'student' OB). My woodworking skills and equipment are marginal compared to (most?) other hobbyists.
So the 1/2 cu ft Dayton cabinets are a compromise (not optimum interior volume for eight A3 drivers) -- If my DIY aperiodic loading concept shows strong promise, maybe next year will spend the big bucks to get a local woodworker to make really good cabinets -- by then should have a better ideas how might improve cabinet width/shape, suppress resonances, improve BSC, and so forth.
BTW, (something to ponder) maybe in a year or two, would like to try/evaluate adding a RAAL ribbon in at say 6 or 7 kHz using some kind of optimum (coherent) group-delay ckt -- dare I say, 'crossover'. Yes the A3 driver has extended resonse out to 22 kHz, but perhaps adding a RAAL might not be so ridiculous with the A3, considering that Vance Dickason, in his recent VC mag review, suggested a 6kHz crossover if a tweeter were to be used with A3s.
Last, but not least: The January 2002 and February 2002 issues of "Audio Express" had a great article about using layers of fiberglass in open-back enclosures ("The Infinite Box Concept") for enhanced bass response & rear-wave reduction, etc. The Feb 02 issue also had interesting 'panel dampening studies'.
Bill