# calculating air space

Discussion in 'Audio' started by Suffergauge, Dec 3, 2002.

1. ### Suffergauge1/2 ton status

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What is the trick to getting it right? I just picked up a pair of mtx 10" subs. Now I need to build a box, just want it to be as close to right as possible.

2. ### Triaged1/2 ton status

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Do you need to know what size box to make?
If so you need to get that info from the manufacturer.
Or do you need to know how to calculate the volume of a non-cubical box?

3. ### Suffergauge1/2 ton status

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How to calculate the volume of the box. So I guess the mathmatical formula.

4. ### Triaged1/2 ton status

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It is
Length * Width * Height
if it is a cube (measured from the inside of course)

If it has a wedge type shape when you look at it from the side then
(top length + bottom length)/2 * width * height

Make sence?

5. ### Suffergauge1/2 ton status

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Makes sence to me. Just emailed mtx for the specs. Thanks triaged.

6. ### BozoWise1/2 ton status

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Should have posted the sub info. I have all of the MTX specs here at work ;-) saved you the time for an email reply.

7. ### '73 K51/2 ton status

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Take the external dimensions of the box, minus the thickness of the wood on each side (should be 3/4 inch MDF), take height x width x depth = Z. The measurements should be all in inches. Then you take Z / 1728 = T. And T is the volume of the box in cubic feet...because there are 1728 cubic inches in a cubic foot. Get it???
Besides subtracting the space that the wood takes up, you'll also want to subtract the airspace that the speaker takes up inside the box (magnet, basket, etc) and any ports if you are using them...bracing too.

8. ### Triaged1/2 ton status

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I would think that the volume that the speaker displaces would be taken into account by the manufacture when they give out the spec's.????

If I am going off of the manufactures ###'s do I have to take it into account?

9. ### '73 K51/2 ton status

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Not all companies do it the same way. JL Audio will give you the internal airspace recommended and also the external dimensions of an example box which takes the speaker volume into account.
My older Rockford stuff never did that. Somewhere around the Thiele/Small parameters in the owners manual, it would tell you the speaker volume and thats it. When they say 2 cubic feet and means ONLY air in the box. They left it up to the owner to subtract it. If you have the owners manual still it should say somewhere in the fine print.

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