This thread is of interest to me as well. I am considering building two sealed enclosures each with an 18" driver.
If i could afford the price I would simply go for the LMS Ultra, but, sadly I am not a rich man.
I have heard said that if I have the option to go with a big cabinet, that, there are other 18" drivers that will give the ultra a run for its money. It seems part of the reason the Ultra is so expensive is the technology that allows it to perform well in a relatively small enclosure.
So, with no limit on cabinet size, can I get some ideas on some drivers that will perform at the level of the ultra?
My mains are Aerial Acoustics LR5 (LCR) so I want to build two subs with sound quality to match the Aerials as well as provide decent output and extension.
I have not yet purchased an amp so that too is wide open for options. I prefer something like the inuke6000 with a built in eq.
Current Equipment: Datasat LS10 w/ Atmos and DIRAC. Datasat RA7300, Aerial Acoustics LR5's (LCR), Aerial Acoustics LR3's (sides), RBH in-walls (rears), Seaton Submersive, Marantz VP15s1, 106" Carada BW screen, Oppo BDP-103.