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bracing calculations for sub box

post #1 of 4
8/31/08 at 5:16pm
Thread Starter 
So I'm 3/4 done one of the sub boxes I'm building but how do I calculate for the bracing?
The box is 24"Wx32"Hx40"L with an internal cubic feet of 15.289

I double braced the back and front and have used 3 pieces of 30.5"x40" for the bracing, with the center cut out to leave a 3" square frame in all of the pieces.

There are three 4" ports at around 25" long (depending on your answers) to give my 16hz tune.

How do I subtract the bracing to know how much I have left?

I know the ports and the sub take up almost 1 cubic foot (ixl-18.2.2)

I can't find a calculator online to do this.

thanks
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post #2 of 4
8/31/08 at 8:26pm
I usually use a spreadsheet to do these sort of calculations. Columns for L, W, D, then fourth column for the product LxWxD. Start with total internal volume calculation, subtract out each brace, then add back each cut-out. Same thing for the ports, except the (presumably cylindrical) port volume would be (Pi)x(W/2)^2xD. In general, you'll find some of these are insignificant effects in a 15+ cu ft box.
Frank
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post #3 of 4
8/31/08 at 8:48pm
BoxNotes will help you with that calculation!

My current project shows that bracing, speaker & port will take up .88 cu.ft.

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post #4 of 4
8/31/08 at 9:52pm
Thread Starter 
ahh sweet, than you!

humm it doesn't really tell you how much you have left after putting as much as you want in though but still helpful and gives me a better idea.
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