The mean of: 25-45 = (35 HZ).
I Have allot of Port length to cut and try out! 10' of 6" PVC.
IM THINKING: 34.8 HZ - 31.5 HZ. (Two Ports).
I'm going interchangeable with ports. Test them out.
Currently I have a 28 HZ Port.
(3) interchangeable ports:
28hz, 31.5HZ, 34.8HZ.