I like all those ideas, but Dan's will prove the easiest and very little work because I already have a sealed cube for a 15. I think it's 90L, so I'll need to shorten the port. I also have an EBS box for a Maelstrom which I think is 360 liters (why aren't those box designs on the Adire site any more?). I was wondering what to do with it anyway since my Maelstrom is part of my dipole bass. It already has dual 17" by 4" flared ports, so I can play with resistance in the port(s) to tune it however I want. I also already have the other flared port.
It won't look pretty, but will be hidden by a false stage. The only work to to is fix one baffle to fit a Tempest, add a port to the cube (the hardest part), and join the boxes.
I'm leaning toward making a sizeable airspace between the 2 drivers which really smooths out the response of the Decware Housewrecker, a 6th order BP design. It I do that, then I can add a removeable plexy window for viewing and driver access. It's a no pressure zone, so plexy is OK. Then just stand this monster up in the one unused corner which just happens to have concrete walls.
The big question is, should I go all the way and intentionally make it look like a cyclops robot? It will be such a monster that it deserves a name, maybe Iron Man, and initiate him with some Sabbath cranked up on the HT system.
This is going to be fun. I'll have to warn the neighbors so they don't think we're having an earthquake because no way 10hz is staying in the room.