Assuming all have the same sealed/ported volume and same port size. I know the pics aren't to scale so don't take that into consideration. I have seen pretty much all of these types used, so I know any would technically work but I wonder about cancellation with all but # 2. The box would be for 8 10's, tuned to 45hz with about 35 cubes total if you're curious. I would have never considered facing subs at each other in the past but I've seen some of the loudest 4th orders with subs facing right at each other like design 1 and 3 so it might not be as much of an issue as I was always told.
All are 4th order walls in case that wasn't obvious and the crap drawing is an overhead shot. I only angled the baffles so you could see how many subs were in each spot in the pics. They would all be straight up and down in the actual build. The port would be centered in all designs except # 2, that would be drivers side.
Here are my personal thoughts on all 4.
# 1. I see this design used all the time so it must work at least ok. I just don't like the idea of a non common chamber as I feel it would be pretty hard to get the cu/ft of both to be identical. I would have thought in the past cancellation would be an issue but as I said above some of the loudest 4th orders I've seen use this layout.
# 2. Common Chamber and no Cancellation issues, so I would think it would do well. However with some subs being much closer to the port I don't know if it would affect output or have issues in that regard.
# 3. Common Chamber but possible cancellation - I don't see many people go this route but I sort of like the design. It keeps the subs in the same chamber and farther from the port.
# 4. Common Chamber with an angled wall. Some say you MUST do angles to avoid cancellation so I figured I'd throw a design in like this. I don't like it because it would be fairly hard to get the cu/ft measurement to be exact. A square is much easier to calculate and build correctly for me personally.
I could also turn the sealed section in design # 2 sideways so all the subs face the port which is how my current setup with 4 10's is, but it isn't a wall. It's just a 16 cu/ft box with the port facing the hatch. Some say they will unload this way, but I currently don't seem to have any issue with that as far as I know. Music played will be a wide variety but the end goal is basically the same as most, stupid low and stupid loud when I play stuff such as Decaf. It has a decent amount of windshield flex now with the 4 but I want more. My amp (MB Quart ONX1600) is 1 ohm stable so I can add 4 more subs and still be fine since I am currently only running it at 2 ohms. It won't double the power but will gain some. It is rated 1,100 @ 2ohms and 1,600 @ 1ohm but in reality it is probably more like 500-700 @ 2 and 800-1,000 @ 1. Subs are my cheapo Lanzars but I ain't got the budget for baller subs.
Thanks for any input you care to provide.