How to build a subwoofer box: plans, cut sheet and tips
Updated October 13, 2026
A good sub box is rigid, airtight and built to the designed net volume. With a cut sheet and a straight saw cut, it is a weekend project.
Materials
- MDF is the standard: dense, flat, cheap, easy to cut and glue. Use ¾″ (18–19 mm) for most boxes; ⅝″ is fine for small 8″ boxes; a double baffle (1½″) helps large or high-power boxes.
- Baltic birch plywood is lighter and stronger, good for boxes that get carried around.
- Wood glue, screws or brad nails, silicone or acrylic sealant, a terminal cup, and carpet or vinyl if you want to cover it.
Plans and cut sheet
Design the box first — volume, port and outside dimensions — then get a cut list: every panel with its size and quantity. Decide which panels overlap which (for example, the top and bottom run full width, the sides fit between them); the cut list must match that choice. Lay the parts out on a 4 × 8 ft sheet with the saw kerf (about ⅛″) between them.
The calculator produces all of this: dimensioned drawings of every panel, the cut list, a sheet layout with kerf, a printable PDF and DXF files if you have access to a CNC router.
Cutting
- Use a table saw or a circular saw with a straight-edge guide; square, straight edges make the box airtight.
- Cut the sub cutout with a jigsaw or a router on a circle jig; check the cutout diameter in the sub's manual — not the nominal size.
- Round ports: drill or cut the hole for the port tube; slot ports are cut from the same sheet as the box.
Assembly
- Dry-fit all panels.
- Glue every joint and pull it together with screws or brads every 4–6″. The glue makes the joint and the seal; the screws only clamp.
- Install the slot-port walls and braces before closing the box.
- Run a bead of sealant along every inside joint.
- Fit the terminal cup, and leave the baffle with the sub opening for last.
Bracing
Large panels flex and waste output. Brace panels longer than about 15–18″ with a dowel or a window brace between opposite walls. Bracing takes up volume — include it in the net volume.
Check it
- Air leaks: gently push the cone in; in a sealed box it should come back slowly. Listen for whistles at high volume.
- Ported tuning: if you have a way to measure impedance, the minimum between the two peaks is the actual tuning frequency. The calculator can recalibrate the port from a measured value.
Get your plans
Pick your sub, set the space and box type, and download the plans, cut sheet, PDF and DXF — free, no signup, in inches or millimeters.