CALCULATING ENCLOSURE VOLUME
It is difficult to give exact box dimensions that are universal for all cars and trucks. It is for this reason that you must be able to calculate the space in which you have available in order to achieve the proper air volume required. It is recommended to build your enclosure from 3/4” thick MDF (medium density fiberboard). Make sure the enclosure is sealed air tight.
Calculating External Volume
1.) To calculate box volume, measure the outside Width x Height x Depth of the enclosure.
Example 12” x 14” x 9” = 1512”.
2.) Next you must convert cubic inches into cubic feet. To do this, you must divide the cubic inch total by 1728”.
Example 1512 
1728 = .875 Cubic feet.
Calculating Internal Volume
1.) To calculate the internal (net) volume of the above box you must first multiply the thickness of the wood you are using by Two (2).
Example 3/4” x 2 = 1.5”.
2.) Next subtract 1.5 from each of the outside measurements of the box.
Width | Height | Depth |
14 | 9 |
3.) Multiply the new totals (H x W x D)
Example: 10.5 x 12.5 x 7.5 = 984.375
4.) Next you must convert cubic inches into cubic feet. To do this, you must divide the cubic inch total by 1728”
Example 984.375 
1728 = .5696 Cubic feet.
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