Subwoofer Box Volume Calculator

When building a subwoofer enclosure, the internal air volume determines how your speaker performs — too big or too small and the bass suffers. Select your enclosure type (rectangular, wedge, or cylindrical), wood thickness, and unit system, then enter your box dimensions to get the internal air volume your subwoofer actually sees. Secondary outputs include external volume, wood volume, and volume in liters.

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Results

Internal Air Volume

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External Volume

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Wood Volume

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Volume (Liters)

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Frequently Asked Questions

What is the difference between internal and external volume?

Internal volume is the air space inside the box available for the subwoofer, while external volume includes the wood material. Internal volume is what matters for subwoofer performance and specifications.

How does wood thickness affect the internal volume?

Thicker wood reduces internal air space. The calculator subtracts the wood volume from the external dimensions to give you the actual internal volume. Typical MDF thicknesses are 1/2", 3/4", or 1".

Which enclosure type is best for my subwoofer?

Rectangular boxes are easiest to build and most common. Wedge enclosures save space in tight installations. Cylindrical enclosures can be stronger but are harder to construct. Check your subwoofer's specifications for recommended volume.

How do I know what volume my subwoofer needs?

Check the manufacturer's specifications for recommended enclosure volume, usually listed as Vb (box volume). This is typically given in cubic feet for sealed boxes or cubic feet plus port tuning for ported boxes.

Can I use this calculator for ported enclosures?

Yes, but remember that ports take up internal volume. Calculate the port volume separately and subtract it from the total internal volume to get the net air space available to the subwoofer.

What if my calculated volume doesn't match the recommended specs?

Adjust your box dimensions proportionally. If you need more volume, increase all dimensions slightly. If you need less volume, reduce dimensions or add internal bracing to take up space.

Should I account for the subwoofer displacement?

Yes, subtract the subwoofer's displacement volume (Vd) from your calculated internal volume. This information is usually provided in the subwoofer specifications, typically 0.05-0.15 ft³ for most car audio subs.