I was hoping to discuss useful topics, like those I listed above.
We already discussed, ad nauseum, the design goals several months ago. I've been doing this for 20 years. Why you would bring this up now makes no sense to me. Start with half a build? Maybe you haven't noticed but the build is essentially finished, so your post makes no sense. This design wasn't built for reproducing down to 15 Hz, the design goal was as flat as possible down to 5 Hz with negligible distortion @ ___ dB in a room size of approximately 10,000-14,000 cubic feet. Also, you don't build two of these subs and come back a year or two later and build two more. These subs are built to last a long time with the highest quality level obtainable via sealed subs. That last octave is a bitch and there is no reason to even have this debate. What would be helpful, however, is to discuss some of the questions I posed above.
Nobody has a problem seeing what the TRW fan subwoofer can do.... however, when you try to build something from multiple sealed subs to try and get close to what a TRW can do in the lowest ocataves, even close, it takes drivers and power. I'm really not interested in having more discussion on that particular subject, however, I am interested to debate about the positioning of these 4 subwoofers as described above.
Hopefully in 1.5-2 years I will be able to independently position them in a 28' x 38' x 12' new construction room... that is the ultimate plan.
For now, in the temporary, current 28 x 18 x 9' room (non sealed and open to other room on one end) the question comes down to:
Assuming I am going to stack two of them, the height will be 43 + 43 = 86" tall. I have a choice of:
1) Left and right: adjacent to the to edge of the 11.5' wide screen, spaced approximately 12' apart.
2) Left and right: towards the corners, spaced approximately 18' apart, one stack in each front corner.
3) All in the left or all in the right corner (2) stacks of (2) side by side.
It is possible I can have the 4 subs independently positioned, but I doubt it. I think that is most likely going to have to wait until I can build a custom room/house some day. I think it is best to treat this situation as if I have two point sources... and I believe the above are my only real choices.
P.S. Subs will be crossed in the 50-60 Hz range...