tommyk90
5,000+ posts
THE WHOLE THING!!!
I said it was a general rule, not words to live by.The DD port area per cubic foot of volume is only to keep things simple for the average Joe who knows nothing about box design.
It is NOT a rule of thumb for every driver out there. I have used some 8" subs that worked really well in a 3 ft^3 enclosure but they sure as hell wouldn't like 45in^2 of port area. It would be too much and waste a ton of space. A pair of them were perfectly fine with about 20in^2 of port area in 5 cubes. Great "rule of thumb" that is.
With that particular sub, I would do about 20-30in^2 though. You could stay around 20in^2 and you should be fine.
I know a TON of drivers that would work just fine with that rule. His sub is no exception. In fact, I bet 95% of drivers out there could follow that rule just fine. Its when you get into crazy, super high performane drivers or super specific alignments/designs that this rule won't work.
Sure, its not going to work for every sub out there in every alignment, no matter what the person is looking for, but for the general person with a normal install that rule will work just fine. If I didn't think it wouldn't work for his install, I wouldn't have mentioned it.