FWIW, back at post #24 I meant to add an edit WRT to cab shape: GM-416-8B MLTL Corner Cabinet


That said, all this room mode, speaker shape musings has turned out to be just a bit of a tutorial that's been needed here for a long time and in some edited form be made a must read 'sticky' before posting speaker design request IMNSHO since after viewing your pictures it's obvious that acoustically your room is anything but a simple 15x30x9 ft rectangle and your floor plan doesn't reflect what's in the pictures, so not a complete waste of everybody's time, but at this point I recommend a curved back to fit the desired net [Vb] and after that it really doesn't matter too much as any near boundary reflections can be dealt with DIY acoustic panels, absorbant tiles, thick rug hangings, 'thick' plant[s] arrangements, etc., determined impirically by ear or 'map' it with computer 3D room measuring software.


To wit: The two? wall offset 'shelf', which probably has little impact on the 1st, 3rd harmonics, will set up it's own lopsided 'secondary room insert' harmonic structure to comb filter with the room's primary 3D one.


Acoustically much worse though is the stairwell that acts as either a low tune Helmholtz resonator or acoustic bandstop filter depending on whether the upstairs door is open or closed, both with a Ql [loss] dependent on how well it seals; so on the one hand it will be a 1/2 WL resonator [vent] tuning the room to some other frequency with its own superimposed 1/4 WL TL pipe action, i.e. make the room a relatively high tuned MLTL in effect [judging by its visible length, net [Vb]; or leave the room a 1/2 WL resonator with a hugh notch in its response somewhere in the [sub?] bass BW.


In ~short and all things considered, if a curved cab is too much hassle, then some form of tapered is desirable, though just make them symmetrical and if they do wind up in the corners, then fill the rear cavity it creates with some form of bass-trap such as rolls of fiberglass attic insulation with holes in its plastic packaging.


GM