Subwoofer Enclosure Calculator

They come from the driver manufacturer's published Thiele-Small parameter spec sheet, not from anything measurable by eye or from the driver's physical size alone. Because every formula in this calculator builds directly on those three figures, entering a slightly wrong value from the wrong datasheet or the wrong driver model will produce a box volume recommendation that's off even if every other input is correct.

A system Q of 0.707 is known as the Butterworth alignment, prized in sealed-box subwoofer design because it produces the flattest possible bass response without a resonant hump above the roll-off point or a premature loss of low end. Building a box either much larger or much smaller than this target trades that flat response for either a boomier peak or reduced output.

A port isn't just a vent — it forms a Helmholtz resonator with the enclosed air, and its length, diameter, and the box volume together determine the exact frequency at which that resonance reinforces bass output. Getting the port dimensions wrong shifts the tuning frequency away from where it's meant to reinforce the driver's output, undermining the extra bass extension a ported box is built to deliver.

It's intentionally simplified — real vented-box design typically references alignment tables like QB3 or SC4 that account for more nuances of the target response than this calculator's straightforward volume and tuning-frequency formulas capture. Use the ported results here as a solid starting point for prototyping, then verify with dedicated box-modeling software before finalizing dimensions and cutting materials.