Sky High Car Audio FXXL-15 D1

15″ subwoofer · dual 1 Ω · 5,000 W RMS

31.2 HzFs, resonance
0.57Qts
2.22 ft³Vas
1.42″Xmax
5,000 WRMS
Sourceskyhighcaraudio.com · manufacturer data
Checked against sourceOctober 2026
Thiele/Small parameterscomplete
Mounting dimensions3 of 4 — missing: magnet diameter; the designer will use an estimate

Recommended box

For a sedan, one sub, 5,000 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
2.22 ft³ (63 L)
Net volume
Bass character (Qtc)Tight and punchy · 0.80
Fc44 Hz
F3 (−3 dB, no cabin gain)41 Hz
Example box (outside)16 15/16″ × 16 15/16″ × 18 11/16″
Open sealed box in designer

Ported

deeper, louder
2.05 ft³ (58 L)
Net volume
Tuning (Fb)34 Hz
Portslot 2 15/16 × 16 5/16″, 48 5/8″ long
Port velocity at 5,000 W95 ft/s
F3 (−3 dB, no cabin gain)32 Hz
Example box (outside)25 3/4″ × 17 11/16″ × 18 1/8″

At 5,000 W this example’s port will be noisy: air speed 95 ft/s, while the limit is 82 ft/s. It stays quiet up to about 3,700 W. Full power needs a port of at least 55.7 in², which means a bigger box than this example — size it in the designer.

Open ported box in designer

Deeper: 4.94 ft³ (140 L) tuned to 27 Hz, 31 1/2″ × 17 11/16″ × 32 15/16″ 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

Size15″
Voice coilsdual 1 Ω
RMS power5,000 W
Fs31.2 Hz
Qts0.57
Qes0.644
Qms4.61
Vas2.22 ft³
Re (one coil)0.64 Ω
Sd127.7 in²
Xmax1.42″
Vd181 in³ calc.
Mms399 g calc.
BL8.8 T·m calc.
EBP48 — suits sealed calc.
Sensitivity, 1 W / 1 m86.7 dB calc.

Mounting dimensions

Ø15 1/2″cutout Ø13 3/4″mounting depth 10 13/16″magnet Ø≈ 8 15/16″
Cutout diameter13 3/4″
Mounting depth10 13/16″
Overall diameter15 1/2″

Judging by its value, the published Re is for both coils in series — converted to per coil.

“≈” 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 Sky High Car Audio 15″ models

Similar 15″ subwoofers from other brands

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

FAQ

What box does the Sky High Car Audio FXXL-15 D1 need?

Recommended net volume: 2.22 ft³ sealed, 2.05 ft³ ported tuned to 34 Hz — for one sub in a sedan at 5,000 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 FXXL-15 D1 Thiele/Small specs?

Fs 31.2 Hz, Qts 0.57, Vas 2.22 ft³, Xmax 1.42″, Sd 127.7 in².

What is the Sky High Car Audio FXXL-15 D1 mounting depth?

Mounting depth is 10 13/16″, cutout diameter 13 3/4″. The inside depth of the box must exceed the mounting depth by at least 1″.

How much power does the Sky High Car Audio FXXL-15 D1 handle and how do I wire it?

RMS power rating: 5,000 W. Dual 1 Ω voice coils: series gives 2 Ω, parallel gives 0.5 Ω at the amp. Wiring for several subs and amp power — in the wiring calculator.