Custom Subwoofer Box Builder

Add the driver's own displacement (typically 0.03-0.3 ft³ for a 12" subwoofer, depending on basket and magnet depth) plus a bracing allowance (0.05-0.08 ft³ is typical for a single brace) on top of the net figure from the spec sheet. Manufacturers occasionally already net these out in their published figure - check whether your driver's datasheet says "net" or "gross" before adding them again.

Because a boot, cabin or custom enclosure location usually leaves depth as the one dimension you can still choose, while width and height are fixed by the space available. If your build is actually constrained on depth instead, run the same arithmetic with depth and one other dimension fixed and solve for the third by hand.

¾" (0.75 in, roughly 18mm) is the standard for car-audio sub boxes and is this tool's default. ½" is sometimes used for smaller single-sub builds to save weight and internal volume, and 1 in is occasionally used for very large or high-SPL builds needing extra rigidity.

Yes, on almost any panel span over about 12 inches unsupported. A single centre brace is the most common approach and typically displaces 0.05-0.08 ft³ - this tool's default bracing allowance sits in that range.

Using one specific, common joint layout: top and bottom panels run the full external width and depth; the two side panels fit between the top and bottom, running the full external depth; and the front and back panels fit between both the top/bottom and the sides. Six panels, three unique sizes.

Not recommended, and this tool doesn't model it. Two different drivers usually want different volumes and tunings, so sharing one chamber compromises both. Build two separate chambers instead, each sized using Number of subwoofers = 1 with that driver's own net volume.

This tool totals the area of all six panels and divides by 30.67 ft² - a standard 8x4 ft sheet's area after a 15% allowance for saw kerf and offcuts - then rounds up. Most single-sub sealed boxes fit comfortably on one sheet; larger ported or dual-sub builds may need two.

Because port length and diameter depend on the box's tuning frequency and final internal volume, which this tool doesn't calculate acoustically - it's a dimensional/cut-list tool, not a tuning tool. Work out the port dimensions with the Speaker Box Port Size Calculator once your box volume is set.

The tool flags any solved depth over about 30 inches as worth double checking - that's larger than most boot or cabin footprints comfortably allow. Reduce the target net volume, increase the fixed width or height if you have room, or reconsider a ported design.

Ported boxes generally need noticeably more net volume than sealed ones for the same driver - commonly 1.5-2.0 ft³ net for a 12" driver in a ported design against roughly 1.0-1.4 ft³ net sealed - plus the port's own displaced volume on top.

No - it's one specific, common convention (top/bottom as the outer pair). Some builders use front/back as the outer pair instead, which shifts a material thickness between the top/bottom and side panel dimensions. The internal volume works out the same either way.

The arithmetic works for any sealed or ported rectangular enclosure, not just subwoofers. Driver displacement and typical net-volume figures for full-range drivers differ from a 12" subwoofer's, so use your own driver's spec rather than this tool's subwoofer-oriented defaults.

No. It turns a target net volume you already have (from the driver's datasheet or acoustic modelling software) into real panel dimensions and a shopping list. It doesn't model frequency response, box Q, or port tuning itself.

Contact the manufacturer or check a dedicated Thiele/Small parameter database - the driver's Vas, Qts and Fs values feed proper box-modelling software that recommends a volume for your target response. Guessing a volume risks a box that's too small or too large for that specific driver.

Most panel saws and DIYers round to the nearest 1mm or 1/16 in in practice, which is finer than this tool's 0.01 in output needs. Rounding down on the outer (top/bottom) panels and up on the inner (front/back) panels is the safer direction if you have to round at all.