Sky High Car Audio FMX-12 D2

12″ subwoofer · dual 2 Ω · 3,500 W RMS

29.3 HzFs, resonance

0.40Qts

0.83 ft³Vas

1.46″Xmax

3,500 WRMS

Source	skyhighcaraudio.com · manufacturer data
Checked against source	October 2026
Thiele/Small parameters	complete
Mounting dimensions	3 of 4 — missing: magnet diameter; the designer will use an estimate

Recommended box

For a sedan, one sub, 3,500 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

0.92 ft³ (26 L)

Net volume

Bass character (Qtc)	Dry and tight · 0.55
Fc	40 Hz
F3 (−3 dB, no cabin gain)	56 Hz
Example box (outside)	14 3/16″ × 14 3/16″ × 12 5/16″

Open sealed box in designer

Ported

deeper, louder

1.13 ft³ (32 L)

Net volume

Tuning (Fb)	32 Hz
Port	slot 1 15/16 × 14 5/16″, 60 3/4″ long
Port velocity at 3,500 W	118 ft/s
F3 (−3 dB, no cabin gain)	29 Hz
Example box (outside)	31 1/2″ × 15 3/4″ × 11 1/4″

At 3,500 W this example’s port will be noisy: air speed 118 ft/s, while the limit is 82 ft/s. It stays quiet up to about 1,650 W. Full power needs a port of at least 40.6 in², which means a bigger box than this example — size it in the designer.

The volume and tuning are the recommendation, but the port doesn’t fit this example box. Size the box and port in the designer.

Open ported box in designer

Deeper: 1.34 ft³ (38 L) tuned to 27 Hz, 18 1/4″ × 15 3/4″ × 12 3/16″ outside — a bigger box with flatter deep bass. Open in the calculator

Where to buy Amazon

Sealed Ported · SPL in dB at 1 W / 1 m, no cabin gain

Thiele/Small parameters

Size	12″
Voice coils	dual 2 Ω
RMS power	3,500 W
Fs	29.3 Hz
Qts	0.40
Qes	0.443
Qms	4.18
Vas	0.83 ft³

Re (one coil)	2.32 Ω
Sd	70.9 in²
Xmax	1.46″
Vd	103.3 in³ calc.
Mms	374 g calc.
BL	19 T·m calc.
EBP	66 — sealed or ported calc.
Sensitivity, 1 W / 1 m	83.2 dB calc.

Mounting dimensions

Cutout diameter	11 1/8″
Mounting depth	9 3/4″
Overall diameter	12 13/16″

“≈” 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

skyhighcaraudio.com/sky-high-car-audio-fmx-series-12-subwoofer/

Other Sky High Car Audio 12″ models

Sky High Car Audio BMX-12 D1 12″ · dual 1 Ω
Sky High Car Audio BMX-12 D2 12″ · dual 2 Ω
Sky High Car Audio FE-12 D2 12″ · dual 2 Ω
Sky High Car Audio FE-12 D4 12″ · dual 4 Ω
Sky High Car Audio FEX-12 D2 12″ · dual 2 Ω
Sky High Car Audio FEX-12 D4 12″ · dual 4 Ω
Sky High Car Audio FMX-12 D1 12″ · dual 1 Ω
Sky High Car Audio FXB-12 D2 12″ · dual 2 Ω
Sky High Car Audio FXB-12 D4 12″ · dual 4 Ω
Sky High Car Audio FXXL-12 D1 12″ · dual 1 Ω
Sky High Car Audio FXXL-12 D2 12″ · dual 2 Ω

Similar 12″ subwoofers from other brands

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

URAL Ultimatum 12 (1+1) 0.97 ft³ sealed · 1.17 ft³ ported
Fi Audio NEO 3.5 12 D1 0.94 ft³ sealed · 2.19 ft³ ported
Fi Audio NEO 3.5 12 D2 0.94 ft³ sealed · 2.19 ft³ ported
Swat HLG-12D2 v.2 0.94 ft³ sealed · 1.20 ft³ ported
AMPIRE BLACK12.2 0.81 ft³ sealed · 2.33 ft³ ported
Deaf Bonce Apocalypse DB-3.5K 12" D1 0.71 ft³ sealed · 1.20 ft³ ported

FAQ

What box does the Sky High Car Audio FMX-12 D2 need?

Recommended net volume: 0.92 ft³ sealed, 1.13 ft³ ported tuned to 32 Hz — for one sub in a sedan at 3,500 W. Fit the box to your space and amp in the free calculator, with plans and a cut sheet.

What are the Sky High Car Audio FMX-12 D2 Thiele/Small specs?

Fs 29.3 Hz, Qts 0.40, Vas 0.83 ft³, Xmax 1.46″, Sd 70.9 in².

What is the Sky High Car Audio FMX-12 D2 mounting depth?

Mounting depth is 9 3/4″, cutout diameter 11 1/8″. The inside depth of the box must exceed the mounting depth by at least 1″.

How much power does the Sky High Car Audio FMX-12 D2 handle and how do I wire it?

RMS power rating: 3,500 W. Dual 2 Ω voice coils: series gives 4 Ω, parallel gives 1 Ω at the amp. Wiring for several subs and amp power — in the wiring calculator.