What if…?
Nearby versions of your design, fully recalculated: box, port, response, excursion. Green means better, red means worse.
Nearby versions of your design, fully recalculated: box, port, response, excursion. Green means better, red means worse.
Sub Box Calculator is a free online subwoofer box calculator and sub box designer for 8, 10, 12, 15 and 18 inch subs. Enter your driver’s Thiele/Small parameters or pick it from the built-in database of about 2,000 models, and it designs a sealed or ported enclosure for your car: net and gross volume in cubic feet, port size and length, frequency response, maximum SPL, cone excursion and port air speed. Then it shows the box in 3D, draws plans of every panel, builds a cut sheet and exports DXF files for CNC cutting.
It runs in your browser with no signup, in inches and cubic feet or in metric units, in English, Portuguese, Spanish and Russian.
It depends on the driver’s Thiele/Small parameters, not just its size. A typical 12 inch sub wants about 1–1.5 cubic feet sealed or 1.5–2.5 cubic feet ported. Pick your model from the database and the calculator works out the recommended volume for it.
A ported box is louder around its tuning frequency and plays deeper for the same power, but it is larger and needs a correctly sized port. A sealed box is smaller, sounds tighter and protects the driver better at the lowest frequencies. The calculator shows the response of both for your driver so you can compare them.
The inside depth must be greater than the sub’s mounting depth, with room for cone travel and air behind the magnet. The rest is set by the volume you need: enter the space you have in the car and the calculator fits width, height and depth to the target net volume.
Not always. In a box that is too small the bass gets boomy and doesn’t go low; in one that is too big the driver handles less power and moves too far at low frequencies. The best volume follows from the driver’s parameters, and the response and excursion graphs show what you gain and what it costs.
Port length follows from the box volume, the tuning frequency and the port area, with end corrections. The calculator computes the length for the tuning you choose, checks air speed in the port so it doesn’t chuff, and can fold a long slot port to fit inside the box.
Gross volume is measured from the outside dimensions of the box. Net volume is the air the sub actually works with: the inside volume minus the driver, the port and any bracing. The calculator shows both and accounts for the material thickness.
Yes: dimensioned plans of every panel, a cut sheet with sizes and quantities, a sheet layout, a printable PDF report and DXF files for a CNC router, in inches or metric. It is all free with no signup; your project stays in your browser, and you can export it to a file or share it with a link.