Tools
Thiele-Small box designer
Enter driver TS parameters to calculate sealed and vented enclosure alignments. Frequency responses are plotted normalised to 0 dB in the passband. Free field — room gain not included.
Driver parameters
Free-air resonance
Total Q
Electrical Q
Mechanical Q
Equivalent volume
Linear excursion
Piston area
DC resistance
Frequency response
Sealed enclosure
Suggested volumes for common Qtc targets
Qtc
0.55
Fc
55.3 Hz
system resonance
F3
72.5 Hz
−3 dB point
Ref. sensitivity
56.9 dB
1W / 1m estimate
Vented (ported) enclosure
Suggested B4 alignment (Keele approximation)
Round, single port
F3
30.0 Hz
−3 dB point
Ref. sensitivity
56.9 dB
1W / 1m estimate
Port length
13.3 cm
at ⌀7 cm
Model assumptions. The vented box response uses the lossless Small (1973) model. Box losses (QL), port losses, and diffraction are not modelled. Real enclosures will roll off sooner at low frequencies.
B4 suggestion. The Keele (1973) approximation assumes the driver is a good candidate for a B4 alignment (EBP ≈ 100). For Qts outside 0.25–0.45, the suggestion is a starting point only — adjust Vb and Fb and observe the response.
Port length. The formula assumes a round, unflanged port with standard end correction (0.732d). A flared port or a flanged end will require a shorter physical tube for the same tuning frequency.
Sensitivity estimate. Derived from the radiation efficiency formula η₀ = 9.64×10⁻¹⁰ × Fs³ × Vas / Qes. Treat as a rough reference figure — actual sensitivity depends on baffle, cone breakup, and measurement conditions.