optimal space for an 18" LMS ultra?

[orangecounty1 10+ year member]

how much space after displacement should a box be for an 18" LMS ultra, on about 2500-3000w? tuning we're going to make around 28hz probably. also, how much port area roughly?

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[Ryan shaw 10+ year member]

5.5 cubic feet tuned at 30 hz with 60-80 sq in" of port is what I got as a response from Kyle at TC. For flat response I believe it is 4.5 cubic feet at 26hz. Depending on what exactly you want I'd say anywhere from 4.5-7 cubic feet tuned from 24-30hz with at least 60"^2 of port would be acceptable