How Many Litres Should a Subwoofer Box Be?
Short answer: a 10″ sub needs about 20–35 L sealed or 30–50 L ported; a 12″ about 30–50 L or 45–70 L; a 15″ about 50–90 L or 70–120 L of net volume. The exact figure depends on the driver's Fs, Qts and Vas.
Typical volumes by driver size
| Driver | Sealed | Ported |
|---|---|---|
| 8″ (20 cm) | 10–20 L | 20–30 L |
| 10″ (25 cm) | 20–35 L | 30–50 L |
| 12″ (30 cm) | 30–50 L | 45–70 L |
| 15″ (38 cm) | 50–90 L | 70–120 L |
| 18″ (46 cm) | 90–140 L | 120–200 L |
These are starting points. A driver with a high Qts wants a bigger box than a low-Qts driver of the same diameter.
Sealed vs ported volume
For a sealed box, the volume sets the system Q (Qtc): about 0.707 gives the flattest response, while a smaller box raises Qtc for warmer, punchier bass. Ported boxes are larger because the box and port work together as a resonator tuned to a chosen frequency (Fb), usually 28–36 Hz in a car.
Bigger or smaller box?
- More volume — deeper bass and more efficiency, but less cone control.
- Less volume — tighter bass and higher power handling, but fewer of the deepest notes.
Always design to net volume: subtract the space taken by the driver, the port and the bracing. The calculator does this automatically.
Frequently asked questions
- How many litres should a 12″ subwoofer box be?
- A sealed box for a 12″ subwoofer is usually 30–50 litres net, and a ported box 45–70 litres. The exact volume depends on the driver's Fs, Qts and Vas.
- How many litres for a 10″ subwoofer?
- For a 10″ subwoofer a sealed box is around 20–35 litres and a ported box 30–50 litres net.
- How many litres for a 15″ subwoofer?
- For a 15″ subwoofer a sealed box is around 50–90 litres and a ported box 70–120 litres net.
- Should I use net or gross volume?
- Manufacturer recommendations are net volume — what is left after subtracting the space taken by the driver, the port and internal bracing.