Altec 421-8H-II vp1

15" · 8 Ω · 150 W · 98.6 dB · datasheet ↗

Thiele-Small parameters

Nominal size	15"
Impedance	8 Ω
Fs	26.9 Hz
Qts	0.272
Qes	0.289
Qms	4.71
Vas	479.3 L
Sd	855.3 cm²
Xmax	1.3 mm
Re	5.67 Ω
Bl	15.7 T·m
Mms	74.8 g
Pe	150 W
Sensitivity	98.6 dB

Alignment hint

EBP	93 · flexible
Sealed Vb (Qtc ≈ 0.71)	≈ 83.2 L

EBP 50-100: works in either a sealed or ported 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
Altec 421-8H-II vp2	25.6 -1.3	0.28 +0.01	501.7 +22.4	1.3 =	98.2 -0.4	close		+
Supravox 400 GN-B	28.5 +1.6	0.272 =	450 -29.3	5 +3.7	98.6 =	close		+
Altec 421-8LF	27.5 +0.6	0.254 -0.02	576 +96.7	1.3 =	99.9 +1.3	close		+
Altec 515-8LF	27.4 +0.5	0.255 -0.02	470.1 -9.2	5.1 +3.8	98.4 -0.2	close		+
Great Plains Audio 515-8LF GPA	27.4 +0.5	0.255 -0.02	470.1 -9.2	5.1 +3.8	98.4 -0.2	close		+
Audio Nirvana CLASSIC 15 FERRITE	24.7 -2.2	0.271 =	551.3 +72	1.1 -0.2	97.3 -1.3	close	80 W vs 150 W: lower power handling · Xmax 1.1 mm < 1.3 mm: lower excursion-limited SPL	+
Altec 604-8H	28.1 +1.2	0.269 =	558.7 +79.4	3.8 +2.5	99.3 +0.7	close	100 W vs 150 W: lower power handling	+
Altec 421-16LF	27 +0.1	0.246 -0.03	600.3 +121	1.3 =	96.8 -1.8	close	16 Ω vs 8 Ω: amp load changes	+
Fluxmag 1504	25.5 -1.4	0.26 -0.01	530 +50.7	4 +2.7	97 -1.6	usable		+
Altec 619-8A	24.6 -2.3	0.241 -0.03	621.3 +142	1.3 =	98.6 =	usable	75 W vs 150 W: lower power handling	+

Compare the closest 3 against the 421-8H-II vp1 →

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.