Optimize your subwoofer enclosure design with our free calculator. Determine the minimum port diameter needed for your bass reflex system to prevent port noise and achieve clear, powerful bass.
Ensure proper airflow velocity for your vented box.
Formula:
Formula for Minimum Port Diameter
The minimum port diameter is determined to prevent excessive air velocity within the port, which causes audible noise (chuffing). The calculation involves the subwoofer's volume displacement, the enclosure's tuning frequency, and a maximum acceptable air velocity.
1. Volume Displacement (Vd):
Vd = Sd × Xmax
2. Minimum Port Area (Ap):
Ap = (Vd × 2π × Fb) / Vp_max
3. Minimum Port Diameter (D):
D = 2 × √(Ap / π)
- Sd: Cone Area (cm²)
- Xmax: Maximum Linear Excursion (mm)
- Fb: Enclosure Tuning Frequency (Hz)
- Vp_max: Maximum Port Air Velocity (m/s, typically 17 m/s to avoid chuffing)