Speaker design calculator

Estimate sealed-box resonance and Q from driver parameters, or find the volume for a chosen target Q.

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Driver free-air resonance Fs (Hz)

Driver total Qts

More inputs and assumptions

Equivalent compliance volume Vas (litres)

Net sealed box air volume Vb (litres)

Target sealed-system Qtc

Answer

…

Estimate sealed-box resonance and Q from driver parameters, or find the volume for a chosen target Q.

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Formula and assumptions

Small-signal, sealed-box model with no added leakage or absorption losses and negligible amplifier/cable resistance. Fc = Fs sqrt(1 + Vas/Vb); Qtc = Qts sqrt(1 + Vas/Vb). The inverse gives Vb = Vas / ((target Qtc/Qts)^2 - 1), requiring target Qtc above Qts. Net volume excludes driver and brace displacement. This does not design ports, crossovers or cabinets, predict maximum output, or guarantee measured frequency response.

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Updated 2026-09-29

Using Speaker design calculator

Estimate sealed-box resonance and Q from driver parameters, or find the volume for a chosen target Q.

Next: Speaker and RF cable calculator

Next: Volume calculator

A worked example

For driver free-air resonance fs (hz) = 18, driver total qts = 0.2, equivalent compliance volume vas (litres) = 139, net sealed box air volume vb (litres) = 47, target sealed-system qtc = 0.4, sealed-box resonance fc (hz) = 35.807999.

Before you use the result

Example results for driver free-air resonance fs (hz)

These examples use Driver total Qts: 0.2; Equivalent compliance volume Vas (litres): 139; Net sealed box air volume Vb (litres): 47; Target sealed-system Qtc: 0.4. They are reference calculations, not recommended settings.

Driver free-air resonance Fs (Hz)	Sealed-box resonance Fc (Hz)
9	17.903999
18	35.807999
36	71.615997

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