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GTmafia.com
03-15-2006, 11:18 PM
I have a box with 2 cubic feet and 2 11"x4" round ports, can you guys help me with what its tuned at? Or help on where to go to figure it out?

Thanks

j3bus2k3
03-15-2006, 11:32 PM
If you can do math failry well by hand, then I'd do this...

http://img118.imageshack.us/img118/6969/fb6eh.jpg (http://imageshack.us)

Where Av is the cross-sectional area of the port (in square inches),
Lv is the length of the port (in inches) and
Vb is the enlcosure's net volume (in cubic inches).

jimmyjames1700
03-15-2006, 11:34 PM
is that 2 cubic feet net, like after port and sub displacement, or total? If you it is net, minus sub displacement and assuming you are using 1/4" sched 40 PVC, you will be tuned at 48.22Hz. That number will go up after mounting a sub in the enclosure unless you plan to invert. I hope that is in the neighborhood of where you wanted to be.

Also keep in mind, tuning will drop considerably after loading and it is interacting with it's surroundings. Must designers tune about 10-13% high purposely to compensate for this. Check JL's website if you are ever curious about this. If you run the numbers for their recommended vented boxes for any of there subs, you will find that what you calculated is a lot higher than what the web site says you will be tuned at.

GTmafia.com
03-16-2006, 12:40 AM
Thanks for the help, I am going to check my measurements/sub dispacement and double check.

nVRuckus
03-16-2006, 09:39 AM
If you can do math failry well by hand, then I'd do this...

http://img118.imageshack.us/img118/6969/fb6eh.jpg (http://imageshack.us)

Where Av is the cross-sectional area of the port (in square inches),

what exactly is "cross-sectional" area?

LuNaTiC
03-16-2006, 11:04 AM
what exactly is "cross-sectional" area?

Port Area.

ngsm13
03-16-2006, 11:14 AM
Port Area.

Precisely. For a slot or rectangular port, it would be Height * Width. For a PVC style port it would be Pi*r^2...

nG