Speaker Box Calculator
Calculate enclosure volume and port length from speaker parameters and a tuning frequency.
Last updated · View algorithm, constants and default inputs (JSON)
About this calculator
Estimate enclosure volume from the entered driver parameters and alignment assumptions, and port length for a ported box. These simplified first-pass calculations omit important driver, displacement, bracing, port-area and air-velocity checks; verify the design against the driver maker’s data before building.
Worked example
calculated with the default values below
Enclosure type Ported box · Vas (equivalent volume) 60 L · Qts 0.4 · Target Qtc (sealed) 0.707 · Tuning frequency 35 Hz · Port diameter 10 cm · Number of ports 1 Enclosure volume 64.89 L · Enclosure volume 2.291 cu ft · Port length 22.32 cm · Port length 8.79 in
General background references
Disclaimer
These calculators give general estimates. Sizing, pricing, availability and standards vary by brand, retailer and country, so treat the output as a starting point and confirm it against the seller's or authority's own figures.
Implementation source
This record describes the implementation used by this page. It is not independent validation. External references, when available, support only the stated formula or definition; estimates and custom rules retain their own assumptions.
Formula and variables
Vb₁ = Vas ÷ ((Qtc÷Qts)² − 1); Vb₂ = 15×Vas×Qts^2.87; L = 23562.5D²Np ÷ (F²Vb₂) − 0.732D
- Vas
- Equivalent compliance volume (L)
- Qts
- Driver total Q
- Qtc
- Target system Q
- F
- Tuning frequency (Hz)
- D
- Port diameter (cm)
- Np
- Number of ports
Sealed volume uses Vas divided by (Qtc/Qts)^2−1 and requires Qtc > Qts. Ported volume is a simplified empirical estimate; port length uses the standard cylindrical-port relationship with input dimensions. Driver displacement, port area/velocity and other design constraints are not modeled. Nonpositive calculated port lengths are left blank.
Frequently asked questions
Are these dimensions a finished enclosure design?
No. Box volume and port length are first-pass estimates from simplified relationships. Driver response, displacement, bracing, port area, air velocity, leakage and manufacturer guidance are not fully modeled. Verify the design with the driver data and an appropriate enclosure tool before building.