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# What is the formula for finding Cubic ft for a speaker box? (1 Viewer)

#### Sebastian

##### Second Unit
Is it HxWxD? or is that surface area?

#### eric nyhof

##### Stunt Coordinator
it is HxWxD, which would be in feet cubed.

Surface area is feet squared and is only the are of a side

#### Dustin B

Senior HTF Member
Don't forget to account for the thickness of the walls, any bracing and any volume displaced by the driver and port if present.

#### Wayne A. Pflughaupt

Moderator
Senior HTF Member
Of course, you have to use the interior H x W x D dimensions, or else subtract the wall thickness from the exterior measurement.

If you are measuring in inches, divide the total cubic inches by 1728 to get the number in cubic ft.:

E.g.:

22” x 18” x 16” = 6336 cu. in.

6336 ÷ 1728 = 3.6 cu. ft.

As Dustin mentioned, you have to subtract the displacement of any braces from that figure (using the same method). Not sure how to figure the displacement of the driver – perhaps the manufacturer could tell you that.

Regards,

Wayne A. Pflughaupt

#### Dustin B

Senior HTF Member
You don't have to be that precise with the driver if you are reasonably precise with the rest. Use 5L for a 15" driver and 3L for a 12" driver. Should be close enough.

#### Sebastian

##### Second Unit
Yeah that is what I thought. I think I may have had square feet confused with Cubit feet.

Thanks guys

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