I'm getting ready to dive into a DIY project, the first subwoofer build since my college car stereo days (~20yrs ago). I was going to wait on the SI18's but the timing is bad. Since I'm putting these behind my screen wall, I need the box to be somewhat shallow. I have flexibility in the other directions to make the box as big as it needs to be. Question is .... is there some laws of speaker building that I would be breaking by building a box with one dimension much smaller than the other two? Most people go more square-ish but I think that is b/c its the most efficient use of space.
Right now I'm looking at two 18s in the front (the priority w/ the new screen wall build) and then adding two SI15 or UM15 subs in the rear. Placement will be on the 1/4 points on the front/back walls. I would prefer to avoid the corners b/c of floor to ceiling bass traps (34" face super chunks). My goal is the drive the 18HOs off a EP4k or 3kDSP in a 4.0 box. I'm currently running two HSU ULS15s that will be sold off.