Subwoofer Box Volume Calculator
Calculate net internal volume of a subwoofer enclosure after accounting for wood thickness and driver displacement.
Results
What is it?
A subwoofer enclosure's net internal volume is the actual air space the driver "sees" — external dimensions minus the volume consumed by the wood panels and the driver basket/magnet assembly. Manufacturers specify optimal enclosure volume (sealed or ported) in their datasheet, and deviating by more than 10–15% noticeably changes frequency response and bass output.
How to use
Enter the external box dimensions, wood thickness (typically 3/4" MDF), the number of drivers, and each driver's displacement from the spec sheet. The net volume in litres, cubic feet, and cubic inches is calculated instantly. Compare with the manufacturer's recommended enclosure volume.
Example scenario
An 18×14×12 inch external box built with 3/4" MDF has inner dimensions of 16.5×12.5×10.5 in = 2165.6 in³. Subtract one 12" driver at 100 in³ displacement → 2065.6 in³ = 33.8 L = 1.20 ft³. A typical 12" woofer wants 1.0–1.5 ft³ sealed.
Pro tip
Enclosure type guidance: if the driver's Qts < 0.4, it is optimised for vented (ported) designs; Qts > 0.7 suits sealed boxes; 0.4–0.7 works in either. Sealed enclosures sound tighter and more accurate; ported designs extend low-frequency output by 3–6 dB but require precise port tuning. Always use 3/4" MDF and brace the interior panels to prevent resonance colouring the sound.