New to Fi and just picked up a 18" btl. Need some suggestions on box size and tuning. I have about 10 cubes gross before driver and port. Looking to do a sub up, port back, tuned to maybe 35hz with 4k of power. A few have said that these have tremendous bottom end so I'd like to tune appropriately.

I'd do 5-8 cubic feet @ 32hz.... with about 12-16 square inches of port area per cubic foot of volume.

I'd do 5-8 cubic feet @ 32hz.... with about 12-16 square inches of port area per cubic foot of volume.

So 128 in of port x 24" length to tune to 32hz?

Personally and from my experience with the 18 BTL I'd do a 7 cubic ft box with about 98 square inches of port...

As far as length @32hz (which sounded the best for daily and great output) you're looking at a port length of about 26.22" long port

Personally and from my experience with the 18 BTL I'd do a 7 cubic ft box with about 98 square inches of port...

As far as length @32hz (which sounded the best for daily and great output) you're looking at a port length of about 26.22" long port

Ok sounds good. Ill try it out and let you know.