B&C 21 SW 150

21.5" · 4 Ω · 1500 W · 99.4 dB · datasheet ↗

Thiele-Small parameters

Nominal size	21.5"
Impedance	4 Ω
Fs	29 Hz
Qts	0.261
Qes	0.27
Qms	8.1
Vas	254 L
Sd	1680 cm²
Xmax	7.5 mm
Re	3.3 Ω
Bl	32.3 T·m
Mms	469.2 g
Pe	1500 W
Sensitivity	99.4 dB

Alignment hint

EBP	107 · ported
Sealed Vb (Qtc ≈ 0.71)	≈ 40.1 L

EBP > 100: favours a ported (bass-reflex) alignment.

Rules of thumb from T/S parameters only. Verify against a real simulation before cutting wood.

Substitute candidates

Driver	Fs (Hz)	Qts	Vas (L)	Xmax (mm)	Sens (dB)	Fit	Notes	Compare
18 Sound 21NLW9000C	29 =	0.248 -0.01	257 +3	8.1 +0.6	100.5 +1.1	close		+
B&C 21 DS 115	30 +1	0.234 -0.03	269 +15	7.6 +0.1	98.7 -0.7	close	8 Ω vs 4 Ω: amp load changes	+
Dayton Audio PSS545HE-4 VORTEX	28.8 -0.2	0.27 +0.01	212.1 -41.9	8.6 +1.1	97.8 -1.6	close		+
LaVoce SAN214.50LD vp	30 +1	0.223 -0.04	250 -4	7.2 -0.3	98.4 -1	close	8 Ω vs 4 Ω: amp load changes · Xmax 7.2 mm < 7.5 mm: lower excursion-limited SPL	+
Beyma 21QLEX1600/Fe	30 +1	0.281 +0.02	309 +55	8.4 +0.9	98.1 -1.3	close	8 Ω vs 4 Ω: amp load changes	+
PD PDN 2151	31.4 +2.4	0.276 +0.02	303.4 +49.4	6.7 -0.8	99 -0.4	close	8 Ω vs 4 Ω: amp load changes · 1000 W vs 1500 W: lower power handling · Xmax 6.7 mm < 7.5 mm: lower excursion-limited SPL	+
Precision Devices PDN 2151	31.4 +2.4	0.276 +0.02	303.4 +49.4	6.7 -0.8	99 -0.4	close	8 Ω vs 4 Ω: amp load changes · 1000 W vs 1500 W: lower power handling · Xmax 6.7 mm < 7.5 mm: lower excursion-limited SPL	+
RCF LF 21N451 v2017	30 +1	0.259 =	375 +121	8.6 +1.1	99.3 -0.1	close	8 Ω vs 4 Ω: amp load changes	+
Eminence NSW6021-6	29 =	0.304 +0.04	224.6 -29.4	10.3 +2.8	97.7 -1.7	close		+
Ciare NDK 21-4	28.5 -0.5	0.322 +0.06	232.4 -21.6	8 +0.5	97.4 -2	usable		+

Compare the closest 3 against the 21 SW 150 →

Ranked on parameter similarity only (Qts, Fs, Vas, Xmax, sensitivity). Same nominal size required. A hint, not a simulation, model the swap before cutting or buying.

Used in enclosures (0)

No enclosure in the catalog uses this driver yet.