I'm pretty sure there's a way to calculate the port tuning of a given speaker cabinet. I just don't know how to do it. Any tips?
I've got a pair of well-made speaker cabinets (1.5" thick panels of birch plywood/mdf, 360 degree bracing) with internal dimensions of 27 x 19 x 17 inches. This does not include the thickness of the acoustic foam that's on five sides of the cabinet or the volume occupied by the bracing.
There are two ports in each cabinet, each 4 inches in diameter and about 4.5-5.0 inches long (hard to be precise because they're flared ports).
When loaded with TAD TL-1601b drivers and crossed over at 650 Hz to a TAD TD-4002 with TAD TH-4001 repro horn they have a thick, congested, boomy sound to them. By contrast, another pair of cabinets with internal dimensions of 27 x 24 x 17 inches and dual ports 4 inches in diameter and 5 inches long produce lively, articulate, well-defined low frequencies with the same drivers and horn.
So, since I'm wondering if the 4 inches larger width of the second cabinet changes the box tuning a great deal, the best way to answer that question is to apply the right formula to calculate the difference.