Sky High Car Audio FXB-8 D2

8″ subwoofer · dual 2 Ω · 500 W RMS

44.4 HzFs, resonance

0.75Qts

0.17 ft³Vas

0.55″Xmax

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, 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

0.35 ft³ (10 L)

Net volume

Bass character (Qtc)	Tight and punchy · 0.91
Fc	54 Hz
F3 (−3 dB, no cabin gain)	46 Hz
Example box (outside)	10 5/8″ × 10 5/8″ × 9 5/16″

Open sealed box in designer

Ported

deeper, louder

0.49 ft³ (14 L)

Net volume

Tuning (Fb)	41 Hz
Port	slot 1 15/16 × 14 5/16″, 86 3/8″ long
Port velocity at 500 W	33 ft/s
F3 (−3 dB, no cabin gain)	34 Hz
Example box (outside)	31 1/2″ × 15 3/4″ × 10 1/16″

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: 1.13 ft³ (32 L) tuned to 31 Hz, 25 11/16″ × 15 3/4″ × 8 1/16″ 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	8″
Voice coils	dual 2 Ω
RMS power	500 W
Fs	44.4 Hz
Qts	0.75
Qes	0.86
Qms	5.8
Vas	0.17 ft³

Re (one coil)	1.9 Ω
Sd	30.3 in²
Xmax	0.55″
Vd	16.7 in³ calc.
Mms	142 g calc.
BL	9.4 T·m calc.
EBP	52 — sealed or ported calc.
Sensitivity, 1 W / 1 m	79 dB calc.

Mounting dimensions

Cutout diameter	7 1/2″
Mounting depth	5 1/2″
Overall diameter	8 3/4″

Cone area (Sd) calculated from Fs, Vas and Mms: 30.3 in².

“≈” 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-fxb-series-8-subwoofer/

Other Sky High Car Audio 8″ models

Sky High Car Audio BMX-8 D1 8″ · dual 1 Ω
Sky High Car Audio BMX-8 D2 8″ · dual 2 Ω
Sky High Car Audio FE-8 D2 8″ · dual 2 Ω
Sky High Car Audio FE-8 D4 8″ · dual 4 Ω
Sky High Car Audio FMX-8 D1 8″ · dual 1 Ω
Sky High Car Audio FMX-8 D2 8″ · dual 2 Ω
Sky High Car Audio FXB-8 D4 8″ · dual 4 Ω

Similar 8″ subwoofers from other brands

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

DD Audio 508e D2 0.32 ft³ sealed · 0.74 ft³ ported
DD Audio 508e D4 0.32 ft³ sealed · 0.74 ft³ ported
Kicker L7 8" 2-Ohm DVC (41L782) 0.53 ft³ sealed · 0.85 ft³ ported
Massive Audio HIPPO XL84R 0.30 ft³ sealed · 0.53 ft³ ported
Kicker Solo-Baric L7X 8" 2-Ohm DVC (49L7X82) 0.41 ft³ sealed · 0.88 ft³ ported
Dayton Audio UMII8-22 0.60 ft³ sealed · 0.49 ft³ ported

FAQ

What box does the Sky High Car Audio FXB-8 D2 need?

Recommended net volume: 0.35 ft³ sealed, 0.49 ft³ ported tuned to 41 Hz — for one sub in a sedan at 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 FXB-8 D2 Thiele/Small specs?

Fs 44.4 Hz, Qts 0.75, Vas 0.17 ft³, Xmax 0.55″, Sd 30.3 in².

What is the Sky High Car Audio FXB-8 D2 mounting depth?

Mounting depth is 5 1/2″, cutout diameter 7 1/2″. The inside depth of the box must exceed the mounting depth by at least 1″.

How much power does the Sky High Car Audio FXB-8 D2 handle and how do I wire it?

RMS power rating: 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.