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Konfusedteen
Dodge Dakota
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12/10/2003
21:31:02
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 Subject: Box Specs.
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how come when I look at a box that says it has say .7 cu. Ft. and i multiply the dimensions and divide by 1728 and then by the # of speakers it holds i never get the same thing the website has???
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Jim Z
GenI
12/10/2003
21:50:35
|  RE: Box Specs.
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How far off are you? can you give an example?
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Konfusedteen
Dodge Dakota
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12/10/2003
22:05:01
| RE: Box Specs.
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http://www.subzoneusa.com/dual_truck.htm
i get 12" h X 8" bd +5"d X 39 1/4" w (8+5/2)
12x6.5x39.25=3061.5 /1728=1.77/2 speakers= .88
they get .66
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DSW
Dodge Dakota
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12/11/2003
04:15:38
| RE: Box Specs.
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You are calculating the exterior of the box, not the interior air volume. What needs to be considered to calculate the interior air volume are the exterior dimensions, minus the thickness of the enclosure material (1/2 or 3/4 MDF?), minus any internal bracing or baffles and the amount of air space the woofer displaces in the box.
12"x6.5"x39.25" minus 1/2" material =11"x5.5"x37.75" (includes internal baffle to seperate enclosures)
11x5.5x37.75 = 2284 cu in, or 1.321 cu ft
1.321 divided by 2 enclosures = .66 cu ft
.66 cu ft minus the speaker displacement ?.08 cu ft? = .58 cu ft
What looked like a .88 cubic foot box was just trimmed down to .58 cu ft internal air volume. If there was any internal bracing you would need to subtract these dimensions and the box would have a smaller volume. If the material thickness of the box was 3/4" the internal air volume would be even smaller.
Best thing to do is figure out 2 fixed dimensions height and width and adjust the last dimension lenght, or what ever works.
lets sayt my box can't be over 12" high and the width can't be over 6", but I need .75 cu ft air volume using 3/4 material and a speaker with .08 cu ft displacement.
12" - 1.5" material thickness = 10.5"
6' - 1.5" material thickness = 4.5"
10.5 x 4.5 = 47.5
.75 cu ft air volume + .08 cu ft speaker displacement = .83 (total box air volume)
1728 x .83 = 1434 cu in
1434 / 47.5 = 30.194 or about 30 1/8"
30 1/8" + 1.5" material thickness = 31 5/8"
Your box would need to be 12"x6"x31 5/8" to get .75 cu ft air volume. Complicated by worth the effort.
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