Polk Audio dX12-8

12″ subwoofer · 8 Ω · 400 W RMS

26.7 HzFs, resonance
0.72Qts
3.09 ft³Vas
0.30″Xmax
400 WRMS
Sourceweb.archive.org · manufacturer data
Checked against sourceOctober 2026
Thiele/Small parameterscomplete
Mounting dimensions1 of 4 — missing: mounting depth, frame outer diameter, magnet diameter; the designer will use an estimate

Recommended box

For a sedan, one sub, 400 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

smaller, tighter
1.80 ft³ (51 L)
Net volume
Bass character (Qtc)Boomy, with a bump · 1.18
Fc44 Hz
F3 (−3 dB, no cabin gain)34 Hz
Example box (outside)31 1/2″ × 15 3/4″ × 9 1/16″
Open sealed box in designer

Ported

deeper, louder
2.37 ft³ (67 L)
Net volume
Tuning (Fb)30 Hz
Portslot 1 9/16 × 14 5/16″, 24 3/8″ long
Port velocity at 400 W51 ft/s
F3 (−3 dB, no cabin gain)29 Hz
Example box (outside)31 1/2″ × 15 3/4″ × 13 1/16″
Open ported box in designer

Deeper: 3.07 ft³ (87 L) tuned to 33 Hz, 31 1/2″ × 15 3/4″ × 15 3/8″ outside — a bigger box with flatter deep bass. Open in the calculator

Where to buy Amazon
203040506080100150200667278849096HzdB
Sealed Ported · SPL in dB at 1 W / 1 m, no cabin gain

Thiele/Small parameters

Size12″
Voice coils8 Ω
RMS power400 W
Fs26.7 Hz
Qts0.72
Qes0.79
Qms7.64
Vas3.09 ft³
Re8.6 Ω
Sd79.7 in²
Xmax0.30″
Vd23.5 in³ calc.
Mms152 g calc.
BL16.7 T·m calc.
EBP34 — suits sealed calc.
Sensitivity, 1 W / 1 m85.2 dB calc.

Mounting dimensions

Ø≈ 12 3/16″cutout Ø11″mounting depth ≈ 5 7/8″magnet Ø≈ 7 3/16″
Cutout diameter11″
Mounting depth≈ 5 7/8″

“≈” 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 Polk Audio 12″ models

Similar 12″ subwoofers from other brands

Close in Fs, Qts and Vas — a box of similar volume will suit them.

FAQ

What box does the Polk Audio dX12-8 need?

Recommended net volume: 1.80 ft³ sealed, 2.37 ft³ ported tuned to 30 Hz — for one sub in a sedan at 400 W. Fit the box to your space and amp in the free calculator, with plans and a cut sheet.

What are the Polk Audio dX12-8 Thiele/Small specs?

Fs 26.7 Hz, Qts 0.72, Vas 3.09 ft³, Xmax 0.30″, Sd 79.7 in².

How much power does the Polk Audio dX12-8 handle and how do I wire it?

RMS power rating: 400 W. Wiring for several subs and amp power — in the wiring calculator.