Sky High Car Audio FE-8 D4

8″ subwoofer · dual 4 Ω · 400 W RMS

50.5 HzFs, resonance

0.85Qts

0.14 ft³Vas

0.55″Xmax

400 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, 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

0.28 ft³ (8 L)

Net volume

Bass character (Qtc)	Boomy, with a bump · 1.04
Fc	62 Hz
F3 (−3 dB, no cabin gain)	49 Hz
Example box (outside)	10 1/4″ × 10 1/4″ × 8 1/2″

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 400 W	30 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: 1.17 ft³ (33 L) tuned to 37 Hz, 28 3/4″ × 15 3/4″ × 7 11/16″ 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 4 Ω
RMS power	400 W
Fs	50.5 Hz
Qts	0.85
Qes	0.98
Qms	6.26
Vas	0.14 ft³

Re (one coil)	3.2 Ω
Sd	30.1 in²
Xmax	0.55″
Vd	16.6 in³ calc.
Mms	129 g calc.
BL	11.6 T·m calc.
EBP	52 — sealed or ported calc.
Sensitivity, 1 W / 1 m	79.3 dB calc.

Mounting dimensions

Cutout diameter	7 1/16″
Mounting depth	5 3/16″
Overall diameter	8 7/16″

Cone area (Sd) calculated from Fs, Vas and Mms: 30.1 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-fe-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 FMX-8 D1 8″ · dual 1 Ω
Sky High Car Audio FMX-8 D2 8″ · dual 2 Ω
Sky High Car Audio FXB-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.

CT Sounds STRATO-8 D4 0.34 ft³ sealed · 0.35 ft³ ported
CT Sounds STRATO-8 D2 0.34 ft³ sealed · 0.35 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
DD Audio 508e D2 0.32 ft³ sealed · 0.74 ft³ ported
DD Audio 508e D4 0.32 ft³ sealed · 0.74 ft³ ported

FAQ

What box does the Sky High Car Audio FE-8 D4 need?

Recommended net volume: 0.28 ft³ sealed, 0.49 ft³ ported tuned to 41 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 Sky High Car Audio FE-8 D4 Thiele/Small specs?

Fs 50.5 Hz, Qts 0.85, Vas 0.14 ft³, Xmax 0.55″, Sd 30.1 in².

What is the Sky High Car Audio FE-8 D4 mounting depth?

Mounting depth is 5 3/16″, cutout diameter 7 1/16″. The inside depth of the box must exceed the mounting depth by at least 1″.

How much power does the Sky High Car Audio FE-8 D4 handle and how do I wire it?

RMS power rating: 400 W. Dual 4 Ω voice coils: series gives 8 Ω, parallel gives 2 Ω at the amp. Wiring for several subs and amp power — in the wiring calculator.