Slot Port Calculator

Calculate rectangular slot port length from box volume, tuning frequency, and port dimensions. Free vented enclosure calculator for DIY speakers.

How the slot port calculator works

Port area is width × height. The same Helmholtz relation as a round port gives effective acoustic length; end correction uses an equivalent diameter 2√(WH/π).

Key terms

  • Slot port - rectangular opening used when round ports are too long or impractical.
  • Equivalent diameter - round port with the same area as the slot, for end correction.
  • Fb - box tuning frequency where port and compliance resonate.

Frequently asked questions

  • When use a slot port? When a round port would be too long for the cabinet or when the baffle layout fits a slot better.
  • How wide should the slot be? Keep port air velocity reasonable at peak excursion; increase area or use multiple ports if velocity is high.