Right you are Dominator,
I did some reading and although I cannot remember where now, I read about a company that was using a dual ported box similar to mine.
There goal is to create two resonant peaks producing greater bass extension. For example at 20hz and 40hz. Fact:The lower the frequency goes, the less the human ear can hear even with the same output. The idea is to create a large peak at 20hz and a smaller one at 40hz. To the ear, this might sound like a flat response even though the actual output is greater at the lower frequencies.
Anyway-this project is no where near that technical, but the article suggested that there long port was approximately twice as long as the shorter one. My short port is 15 inches and my long port is 31 inches.
Again let me say, this was a total shot in the dark and for fun given that I had no T/S parameter. There is some cancellation that I have yet to really try to narrow down and I am suspecting that the long port sub is behaving more like a free air sub than a ported sub. Its port just may be tooooo long! I dunno.
Once the insulation is complete-I will listen critically. But two tuning frequencies was the goal.
Thanks,
Dominick