@devinplombier
Are your cabinets partitioned horizontally so that each driver has its own sealed enclosure? It’s hard to tell from the drawing you posted.
No, the horizontal braces are well ventilated. Since the drivers are identical AND they will have the same electrical signal there is no need to isolate the cabinet spaces. Also solid bracing reduces the internal volume so would require a larger cabinet.
See Troels Gravesen’s site for other ways of using ventilated bracing, and for fun look up the B&W Matrix designs.
Also, what is the rationale for the recessed amp housing compartment
Aesthetics. This is how they were designed to be installed. . See the back of any powered subwoofer ever made.
and wouldn’t it be preferable, generally speaking, to leave the inside back panel of the enclosure flat?
Not really. In truth many have suggested that turning the insides of a speaker into a kind of diffuse field that avoids coherent (i.e. flat) reflections is the way to go. At the wavelengths involved here ~ 7' I'm not concerned.
That could be done simply by knocking out the amp housing, which would also provide opportunities to implement better ventilation for your amps, which will need a lot of it
The enclosure for the amp is really to reduce the opportunity for microphonics and long term part stability. The enclosure is, again, as recommended by the manufacturer. Alternatively you can avoid using the enclosure altogether if you can guarantee a minimum of spacing between them and anything flammable.
@clio09
I have 4 of the RSS265HF-8 woofers sitting around doing nothing that I was going to sell. Now you have given me something to think about as I need to downsize as well.
I’m glad I could tickle your own interest. While I did opt for 2 cabinets you could also consider using only 1 woofer per cabinet and 2-way amps instead of three, perhaps giving you the ability to put a cabinet under each surround speaker as well, if you were so inclined. The drivers however are not the most expensive part of these builds. The cabinet and amps are.