thegr8cody Posted January 24, 2008 Report Share Posted January 24, 2008 can anyone break down the port calculating formula i dont have specs on my sub and it looks like im gonna have to build it off specs of my btl 1998 gmc sierra h/u:eclipse cd3200 sub:dd9518g d1.5 amp:jl e300/4 sub amp:dd m2a front stage:id ctx65cs dc power 270 alt lots of kicker 1/0 Link to comment Share on other sites More sharing options...
Aaron813 Posted January 24, 2008 Report Share Posted January 24, 2008 Re audio port calculator is your friend Link to comment Share on other sites More sharing options...
gotFI? Posted January 24, 2008 Report Share Posted January 24, 2008 www.reaudio.com Link to comment Share on other sites More sharing options...
thegr8cody Posted January 24, 2008 Author Report Share Posted January 24, 2008 i did that but now its tuning it at 28hz maybe i can cut like 3 inches off to raise it 1998 gmc sierra h/u:eclipse cd3200 sub:dd9518g d1.5 amp:jl e300/4 sub amp:dd m2a front stage:id ctx65cs dc power 270 alt lots of kicker 1/0 Link to comment Share on other sites More sharing options...
gotFI? Posted January 24, 2008 Report Share Posted January 24, 2008 but then your internal ft3 changes too Link to comment Share on other sites More sharing options...
andym85 Posted January 24, 2008 Report Share Posted January 24, 2008 Av = vent area Lv = effective length of vent (effective length = physical length + end correction <---1/2 of the ports width) Vb= net volume in cubic inches Fb = tuning frequency Fb = .159*((Av(1.84*10^8)/(Vb(Lv+.823*Av^.5))^.5 Av...just your ports height * width=port area Lv...dont measure the wood used for the port to find length. you want to measure down the dead middle of the port like in the pic below...and if your port uses at least one box wall as part of the port (like this one does) then you need to add half of the ports width to the length to get the effective length (in the pic below this would be an addition of 1.5") the port displacement also needs to be subtracted from the box volume...its the air space inside the port plus the wood used for the port itself.... as you will find out it kind of becomes a kind of a circular equation....as where changing your ports size will directly affect the box volume, therefore directly affecting your tuning basically once you have ur vent area and internal box volume (Vb in cubic inches) then you just play with the length of the port until you find whatever frequency ur looking for i likes me some audio stuff... Link to comment Share on other sites More sharing options...
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