if u have a regular internal port that needs to be say for example 20" long to get a 30hz fq.....would it still need the same 20" length if it was external to get the same 30Hz tuning? I know internal volume would be more considering less displacement

Edited June 25, 200916 yr by SKEEMASK

Yes it still needs to be the same length, because the sub will still see the same volume. It's just that instead of having to build the box to 5 cubes with the internal port, for example, you could only build it 4 cubes because you don't have to account for port displacement inside the box.

appreciate that