Alpine SWA-12S4 (Atom)

12″ subwoofer · 4 Ω · 250 W RMS

Fs 30 HzQts 0.49Vas 2.39 ft³Xmax 0.39″

Recommended box

For a sedan, one sub, 250 W. It’s the same math as the designer’s step-by-step mode, where you can fit the box to your space, vehicle and amp and get plans, a cut sheet and DXF.

Sealed

Net volume1.48 ft³ (42 L)
Qtc0.80
Fc49 Hz
F3 (−3 dB, no cabin gain)46 Hz
Example box (outside)13 3/4″ × 13 3/4″ × 19 3/8″
Open sealed box in designer

Ported

Net volume2.72 ft³ (77 L)
Tuning (Fb)33 Hz
Portslot 1 9/16 × 14 5/16″, 16 7/16″ long
Port velocity at 250 W59 ft/s
F3 (−3 dB, no cabin gain)30 Hz
Example box (outside)31 1/2″ × 15 3/4″ × 13 7/8″
Open ported box in designer
203040506080100150200667278849096HzdB
Sealed Ported · SPL in dB at 1 W / 1 m, no cabin gain

Thiele/Small parameters

Fs30 Hz
Qts0.49
Qes0.53
Qms7.07
Vas2.39 ft³
Re3.6 Ω
Sd70.1 in²
Xmax0.39″
Vd27.6 in³ calc.
Mms120 g calc.
BL12.4 T·m calc.
EBP57 — sealed or ported calc.
Sensitivity, 1 W / 1 m87.4 dB calc.

General

Size12″
Voice coils4 Ω
RMS power250 W

Mounting dimensions

Ø12 5/8″cutout Ø10 9/16″mounting depth 5 9/16″magnet Ø≈ 6 7/8″
Cutout diameter10 9/16″
Mounting depth5 9/16″
Overall diameter12 5/8″

“≈” means the value isn’t in the spec sheet and a typical value for the size is used; “calc.” means it’s calculated from the published parameters. Check the manufacturer’s spec sheet before you build.

Data sources

Other Alpine 12″ models