Hey Scotty, what do you think about these driver placements on my front/rear walls?
They all follow the CABS placement rules pretty closely... except for the 3 driver version, where the top driver is centered between where the two top drivers would be if the room was cuboid, but the distance between the 3 drivers is not constant like it should.
I'm not sure if distance to the wall is more important than driver spacing, and with my wall shape one of them has to give. However, the one with 2 drivers per wall seems to fit all the rules despite the slant ceiling.
Please don't advise the one with 14 drivers per wall.
I only did that because I like playing with CAD, although it would be fun to hear it.
I think the CABS concept of wall reflections is key to making compromises like this work, but I'm still trying to wrap my head around that. The reflection idea suggests that there will be sound bouncing back and forth across the side walls and floor/ceiling while traveling toward the rear, but I'm not sure why that is significant. It seems to me that the only thing that matters is having the radius of individual wavefronts large enough to they are flat enough to merge into one relatively flat wave. So that the bumpiness of the wave front due to multiple drivers is of small enough deviation to be small error during the cancellation. Due to wall reflections and arbitrary room length the phase bumps in the wavefront will not stay in the same location relative to the pitching and catching walls throughout the trip. So the wave has to be flat enough to allow the dips to migrate randomly across the planar wave and still be flat enough to be cancelled with decent efficiency. Make sense to you?
So then what happens if there is only one driver in the center of each wall? How do you calculate Fc? Would CABS even work? The wavefront will be hemispherical coming from one driver, so to flatten it sufficiently to be cancellable at the rear the 1/2 wavelength should be largest wall dimension? In my case Fc = 49Hz. But my fundamental room modes are 36, 49, 70. So CABS with Fc = 49Hz can't prevent the floor ceiling mode at 70Hz. So I need at least 2 drivers per wall.
Considering the small window in the center of the front wall and the need for a entry door on the rear wall, (and my driver and amp budget) I think my best option is 2 drivers per wall.