The only way I know how to lower a port tuning frequency is by enlarging a box, I don't know any other calculations. I want to place a pair of 10's in a port slotted box tuned to 25 Hz. The catch is the box must be a certain size for my trunk configuration. I want the response pretty linear between 25-60 Hz, with the roll-off occuring below 25 Hz because I personaly cant hear much below that point. I know that in a choice between high efficiency, small box size, and low end extension you cant have all three, so I am willing to lose alot of efficiency, my box is of fixed external dimensions, and my goal is reasonably flat output down to the mid 20's. I'm assuming that since the manufacturer frequency responce is rated down to 22 Hz my goal is realistic. Its a tough question but I'm totaly serious about it, and any help would be greatly appreciated. If its an unlikely idea or theres a better option out there please explain. I had them in a sealed box but I think this is a better option to keep the lows on par with the upper range. Thanks.
Box: Face 13" x 35 1/4" (About 3.15 ft^3 internal, ports must be on face)
Depth 15 1/2" (External dimensions, cannot be changed)
Subs: 2x Audiobahn AW1006T
Flame Q's (Don't laugh, I got a good deal a long while back)
Fs: 35.2 Hz
Qts: 0.72
Vas: 12 liters or 0.42 ft^3
Qes: 0.89
Qms: 3.93
EBP: 40
Box: Face 13" x 35 1/4" (About 3.15 ft^3 internal, ports must be on face)
Depth 15 1/2" (External dimensions, cannot be changed)
Subs: 2x Audiobahn AW1006T
Flame Q's (Don't laugh, I got a good deal a long while back)
Fs: 35.2 Hz
Qts: 0.72
Vas: 12 liters or 0.42 ft^3
Qes: 0.89
Qms: 3.93
EBP: 40