Ok, I think i've decided on a pair of AudioQue SD 2.5 10" subs and gonna put an old Planet audio 1250.1 on em in a Ford Flex. Its been a while since i built a box so someone check my math. I talked to the tech and he said those 10's like 1.2 cuft after all displacements, and they recommend 16 sq in of port per sub. So I figured this would be my box. 12" deep, 12" high, and 37" wide (this is how it has to be to fit where i want it). With 2 subs, I will do a slot vent of 2.75 wide and 12" high. I figured it would be 25.5" long would give me 35 Hz.
Port Disp = .48
Driver displacement = .20 for both
Gross internal volume before all displacements is 3.08 cu ft.
Minus all displacements i'm right on my goal of 2.4 cu ft. net for the 2 tens. Can someone double check my port figures, I got some conflicting info from a couple sites. How important is making the 45 degree bend in the vent as it turns the corner to run along the back of the box? What if I wanted to use round ports? Like precision or aero ports? From what i can see, the round port would be too long to fire out of the same panel as the woofers, I would have to fire it out the side, which would loose some spl to my understanding.
Assuming 3/4in MDF I get .62 cu ft displacement for the vent (also assuming you meant the vent opening is 2.75, not 2in plus 3/4 for the wood). All other calculations look good. You might hear some people say "don't use the same height X depth, standing waves, etc" but I think you'll be fine, might want to deaden one panel with some poly batting if you're worried about that. Also I don't personally think you'll ever notice if you skip the 45.
Considering .62 displacement for the vent, I get 26in even in length for 35hz, 37hz would be 22in in length, so anywhere in that range will be extremely close to what you're looking for. I would go 26in flat and call it a day. With the added displacement of the extra inch of port (.63 so enclosure would measure 2.25 total) the vent for 35hz is supposed to be 26.15.
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