# Speaker Box Calculator

Calculate internal volume for speaker enclosure design. Enter box dimensions, driver displacement, and bracing to find net volume in cubic feet and liters.

## What this calculates

Building a speaker enclosure? Enter your internal box dimensions to calculate the gross and net internal volume in cubic feet and liters. The calculator accounts for driver displacement and internal bracing to give you the actual usable volume your speaker driver will see.

## Inputs

- **Internal Width** (inches) — min 1 — Internal width of the enclosure
- **Internal Height** (inches) — min 1 — Internal height of the enclosure
- **Internal Depth** (inches) — min 1 — Internal depth of the enclosure
- **Driver Displacement** (cubic inches) — min 0 — Volume displaced by the speaker driver (from spec sheet). Enter 0 to skip.
- **Bracing/Port Displacement** (cubic inches) — min 0 — Volume taken up by internal bracing, ports, or stuffing. Enter 0 to skip.
- **Enclosure Type** — options: Sealed (Acoustic Suspension), Ported (Bass Reflex), Bandpass

## Outputs

- **Gross Internal Volume** — Total internal volume before subtracting displacements
- **Net Internal Volume** — Usable volume after driver and bracing displacement
- **Net Volume (Liters)**
- **Size Guidance** — formatted as text — General guidance on enclosure sizing

## Details

Getting the enclosure volume right is critical for speaker performance. Too small and the bass sounds thin and boomy. Too large and the bass becomes loose and undefined. Every speaker driver has a recommended enclosure volume in its spec sheet (Thiele-Small parameters).

Enclosure types:

  - Sealed (acoustic suspension): Tight, accurate bass with a gentle roll-off. Easier to build. Requires less volume than ported designs.

  - Ported (bass reflex): Louder bass output and deeper extension, but steeper roll-off below tuning frequency. Needs more volume and careful port tuning.

  - Bandpass: Driver is fully enclosed between two chambers. Narrow but very loud frequency response. Complex to design correctly.

Always measure internal dimensions (not external). Subtract wall thickness from the outside measurements. For 3/4-inch MDF, subtract 1.5 inches from each dimension (two walls).

## Frequently Asked Questions

**Q: How do I find the driver displacement volume?**

A: Check the driver's spec sheet or Thiele-Small parameters. It is usually listed as Vd (driver displacement volume) in cubic inches or liters. If not listed, a rough estimate is 0.05 cubic feet (86 cubic inches) for a 10-inch driver, 0.07 for a 12-inch, and 0.1 for a 15-inch.

**Q: Should I measure inside or outside dimensions?**

A: Always measure inside dimensions. The internal volume is what matters for speaker performance. If you only know outside dimensions, subtract twice the wall thickness from each measurement. Standard MDF is 3/4 inch thick, so subtract 1.5 inches per dimension.

**Q: What is the difference between sealed and ported?**

A: Sealed enclosures produce tight, accurate bass with a gentle roll-off, and they are easier to build. Ported enclosures are louder and extend deeper but have a steep roll-off below the port tuning frequency. Ported boxes need more internal volume and careful port sizing.

**Q: How much does bracing reduce the internal volume?**

A: A typical internal brace reduces volume by about 10 to 30 cubic inches depending on size and material. Two or three braces in a medium subwoofer box might displace a total of 40 to 80 cubic inches. Fiberglass stuffing also displaces volume, about 10-15% of the gross.

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Source: https://vastcalc.com/calculators/everyday/speaker-box
Category: Everyday Life
Last updated: 2026-04-08