SB Acoustics SB12NRX25-8
woofer · EBP 139 → suits a ported box · nominal (full) — SB Acoustics datasheet (https://sbacoustics.com/wp-content/uploads/2021/03/4in-SB12NRX25-8.pdf)
Thiele/Small parameters
| Fs (resonance) | 57 Hz |
| Qts | 0.37 |
| Qes / Qms | 0.41 / 4.1 |
| Vas | 5.3 L |
| Re / nominal Z | 6.4 Ω / 8 Ω |
| Xmax | — |
| Sensitivity | 85.6 dB (1 W/1 m, calc); 85.5 dB (2.83 V/1 m, mfr) |
| Power handling | 30 W |
Published (nominal) values, params full — verify by measurement (DATS/REW) before building.
Datasheet (PDF) ↗ — manufacturer-hosted
Recommended enclosures
| Sealed (Qtc 0.707) — Vb | 2.0 L |
| Sealed — Fc / F3 | 108.9 / 108.9 Hz |
| Ported (suggested) — Vb | 4.0 L |
| Ported — Fb / F3 | 62.3 / 63.1 Hz |
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About this driver
The SB Acoustics SB12NRX25-8 is a woofer with a free-air resonance of 57 Hz and a total Q (Qts) of 0.37. Its efficiency-bandwidth product (EBP) of 139 points toward a ported alignment. In a 2.0 L sealed box it reaches an F3 of 108.9 Hz (Qtc 0.707); a suggested 4.0 L box tuned to 62.3 Hz extends to about 63.1 Hz. See the sealed vs ported guide for how to choose.
Recommended partners
modeled estimateThese tweeters could pair with the SB Acoustics SB12NRX25-8 in a two-way design, but the seed Thiele/Small data is too thin to grade the match yet — add or measure T/S (Fs, Sd, Xmax) to compute a real compatibility grade. You can still open a pair in the guided builder.
- Dayton Audio AMT-Mini-8Insufficient data to grade
Crossover not modelable yet — tweeter needs published Thiele/Small data.
Build this pair → - Dayton Audio AMT2-4Insufficient data to grade
Crossover not modelable yet — tweeter needs published Thiele/Small data.
Build this pair → - Dayton Audio AMT3-4Insufficient data to grade
Crossover not modelable yet — tweeter needs published Thiele/Small data.
Build this pair → - Dayton Audio AMTPOD-4Insufficient data to grade
Crossover not modelable yet — tweeter needs published Thiele/Small data.
Build this pair → - Dayton Audio AMTPRO-4Insufficient data to grade
Crossover not modelable yet — tweeter needs published Thiele/Small data.
Build this pair → - Dayton Audio AN25F-4Insufficient data to grade
Crossover not modelable yet — tweeter needs published Thiele/Small data.
Build this pair →
Modeled estimate from T/S + geometry — no measurements. The verdict is robust; it improves with measured FRD/ZMA data.