18 Sound 21iD

21" · 2 Ω · 1800 W · 94.2 dB · datasheet ↗

Thiele-Small parameters

Nominal size	21"
Impedance	2 Ω
Fs	38 Hz
Qts	0.23
Qes	0.24
Qms	5.6
Vas	143 L
Sd	1660 cm²
Xmax	14 mm
Re	1.3 Ω
Bl	25.2 T·m
Mms	489 g
Pe	1800 W
Sensitivity	94.2 dB

Alignment hint

EBP	158 · ported
Sealed Vb (Qtc ≈ 0.71)	≈ 16.9 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 21NLW9601C	38 =	0.29 +0.06	140 -3	14 =	94.5 +0.3	close	4 Ω vs 2 Ω: amp load changes	+
B&C 21IPAL	37 -1	0.21 -0.02	155 +12	22 +8	99 +4.8	usable	1 Ω vs 2 Ω: amp load changes	+
18 Sound 21NLW9601	37 -1	0.29 +0.06	175 +32	14 =	98 +3.8	usable	8 Ω vs 2 Ω: amp load changes	+
18 Sound 21NLW9601	41 +3	0.32 +0.09	123 -20	14 =	98 +3.8	usable	4 Ω vs 2 Ω: amp load changes	+
Faital PRO 21XL3000	32 -6	0.22 -0.01	223.5 +80.5	17.67 +3.67	98 +3.8	usable	4 Ω vs 2 Ω: amp load changes	+
B&C 21DS115	34 -4	0.27 +0.04	204 +61	16.5 +2.5	99 +4.8	usable	8 Ω vs 2 Ω: amp load changes	+
B&C 21SW152	32 -6	0.3 +0.07	200 +57	15 +1	96 +1.8	usable	4 Ω vs 2 Ω: amp load changes	+
Lavoce SAN215.30	35 -3	0.33 +0.1	200 +57	14.9 +0.9	95.7 +1.5	usable	8 Ω vs 2 Ω: amp load changes	+
B&C 21DS115	32 -6	0.21 -0.02	219 +76	15 +1	100 +5.8	usable	4 Ω vs 2 Ω: amp load changes	+
RCF LF21N551	35 -3	0.33 +0.1	200 +57	15 +1	97 +2.8	usable	8 Ω vs 2 Ω: amp load changes	+

Compare the closest 3 against the 21iD →

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.