Sine Design

Dayton Audio SIG225-4

woofer · EBP 89 → suits either box · nominal (full) — Dayton Audio datasheet (https://www.daytonaudio.com/images/resources/295-656--dayton-audio-sig225-4-specification-sheet.pdf)

Thiele/Small parameters

Fs (resonance)40 Hz
Qts0.43
Qes / Qms0.45 / 8.87
Vas29.7 L
Re / nominal Z3.9 Ω / 4 Ω
Xmax6.0 mm
Sensitivity88.1 dB (1 W/1 m, calc); 91.4 dB (2.83 V/1 m, mfr)
Power handling100 W

Published (nominal) values, params full — verify by measurement (DATS/REW) before building.

Datasheet (PDF) ↗ — manufacturer-hosted

Recommended enclosures

Sealed (Qtc 0.707) — Vb17.4 L
Sealed — Fc / F365.8 / 65.8 Hz
Ported (suggested) — Vb36.7 L
Ported — Fb / F337.5 / 35.5 Hz
Open in designer →Use my measured parameters →Buy at Parts Express →

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About this driver

The Dayton Audio SIG225-4 is a 8.5″ woofer with a free-air resonance of 40 Hz and a total Q (Qts) of 0.43. Its efficiency-bandwidth product (EBP) of 89 points toward either alignment. In a 17.4 L sealed box it reaches an F3 of 65.8 Hz (Qtc 0.707); a suggested 36.7 L box tuned to 37.5 Hz extends to about 35.5 Hz. See the sealed vs ported guide for how to choose.

Recommended partners

modeled estimate

The tweeters below pair well with the Dayton Audio SIG225-4 in a two-way design — each grade is a modeled estimate of the crossover match, with a suggested crossover point. Open any pair in the guided builder to design the crossover and total the parts.

Modeled estimate from T/S + geometry — no measurements. The verdict is robust; it improves with measured FRD/ZMA data.

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