From what I have read, an LLT. I would like a box less then 10 cu/ft per sub if possible with no port noise above 15Hz. Any ideas?
LLT would be the way to go I think. If you can afford some PRs you can get away with an easier build. You'd need 4 of them though.
I think one EP2500 is a bit weak, don't you think? What are your M-X, dual 2ohm or dual 4 ohm? If dual 4 ohm you could parallel the VCs and run the EP2500 in stereo mode, and you'd get, I don't know, 1000 watts or so per woofer. Perhaps that is enough...
If you go with 8cu ft tuned to 18Hz. a subsonic filter at 11Hz (4th order), you don't reach excursion with 1000 watts. With two 6" ports each 54,15" long, port speed isn't really an issue (18m/s @ 16Hz full output), which AFAIK a 6" port can handle without chuffing or noise.
The bigger the enclosure the better, as the port length decreases with box size. 9cu ft with 2 6" ports perhaps?
Why don't you build an EBS
, 16cu ft, that would give you INSANE output in the low 10's.
Maybe a single 8" port is enough? Then the lengths are 46.18" and 40.41". Then you never reach 20m/s on the 8cu ft box.