View Full Version : finding cu. airspace on box?

06-29-2008, 05:07 PM
How do I find the airspace on a box that the face slants at a angle? thanks

06-29-2008, 05:10 PM
Hope this helps..........

Calculating Speaker Enclosure Volume

As you already know, for speakers (especially woofers) to work properly, they must be in the proper size enclosure. The manufacturer can give you the required enclosure volume but can't give the exact dimensions of an enclosure that will work in all vehicles. So that you can build an enclosure of the proper size for your vehicle, this page will explain how you calculate the total volume of the enclosure.

Magic number:

OK... It's not magic but the number is 1728. If you forget it, just remember that the number is 12 inches X 12 inches X 12 inches. 12 X 12 X 12 = 1728.

Square or Rectangular Enclosures:

These boxes are the easiest to calculate the internal volume. You simply measure the height, width and depth (in inches), multiply them together and then divide that number by 1728. If the box has internal measurements of 6" high x 18" wide x 12" deep then the volume of the box is 1296/1728=.75 ft³.

Wedge Enclosures:

Since wedges are comprised of two shapes, a rectangle and a triangle, they are fairly easy to caculate as well. Simply seperate the shapes, and calculate for each. Use the same method above for the internal measurements of a rectangle, then use (H X W X D) / 2 for the triangles internal volume. Add these together to get your total internal volume.

Area (rectangle) = Height x Width
Area (triangle) = 1/2 Height x Width
Area (circle) = 3.141592654 x Radius²

Area (circle) = .7853981634 x Diameter²

Volume (rectangular box) = Area (of one side) x Depth
Volume (triangular enclosure) = Area (triangle) x Depth
Volume (cylinder) = Area (circle) x Depth

1728 Cubic Inches = 1 Cubic Foot
28 Liters = 1 Cubic Foot

If you want to compensate for the volume taken up by the woofer, you can use the following approximations. Keep in mind that these are for 'normal' woofers. If you're using a competition woofer with a huge frame and magnet structure, refer to the manufacturer for the actual displacement volume of the woofer. Even if you're not using competition woofers, most high quality manufacturers provide this spec in the woofer's datasheet.

8" = .03 ft³
10" = .05 ft³
12" = .07 ft³
15" = .10 ft³

06-29-2008, 05:11 PM
add top and bottom together...multiply by .5 then multiply length x height...divide by 1728 :)

06-29-2008, 05:12 PM
that is internal measurements...btw ;)