Sky High Car Audio BMX-18 D2

18″ subwoofer · dual 2 Ω · 2,500 W RMS

20.5 HzFs, resonance

0.51Qts

7.60 ft³Vas

1.26″Xmax

2,500 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, 2,500 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

4.45 ft³ (126 L)

Net volume

Bass character (Qtc)	Tight and punchy · 0.84
Fc	34 Hz
F3 (−3 dB, no cabin gain)	31 Hz
Example box (outside)	31 1/2″ × 20 1/2″ × 15 11/16″

Open sealed box in designer

Ported

deeper, louder

5.76 ft³ (163 L)

Net volume

Tuning (Fb)	30 Hz
Port	slot 4 1/2 × 19 1/16″, 36 13/16″ long
Port velocity at 2,500 W	64 ft/s
F3 (−3 dB, no cabin gain)	26 Hz
Example box (outside)	31 1/2″ × 20 1/2″ × 25 13/16″

Open ported box in designer

Deeper: 7.56 ft³ (214 L) tuned to 25 Hz, 31 1/2″ × 20 1/2″ × 32 9/16″ 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	18″
Voice coils	dual 2 Ω
RMS power	2,500 W
Fs	20.5 Hz
Qts	0.51
Qes	0.564
Qms	5.51
Vas	7.60 ft³

Re (one coil)	2.41 Ω
Sd	194.9 in²
Xmax	1.26″
Vd	245.5 in³ calc.
Mms	626 g calc.
BL	18.6 T·m calc.
EBP	36 — suits sealed calc.
Sensitivity, 1 W / 1 m	87.2 dB calc.

Mounting dimensions

Cutout diameter	16 5/8″
Mounting depth	11 7/16″
Overall diameter	18 1/2″

“≈” 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-bmx-series-18-subwoofer/

Other Sky High Car Audio 18″ models

Sky High Car Audio BMX-18 D1 18″ · dual 1 Ω
Sky High Car Audio FEX-18 D2 18″ · dual 2 Ω
Sky High Car Audio FEX-18 D4 18″ · dual 4 Ω
Sky High Car Audio FMX-18 D1 18″ · dual 1 Ω
Sky High Car Audio FMX-18 D2 18″ · dual 2 Ω
Sky High Car Audio FXB-18 D2 18″ · dual 2 Ω
Sky High Car Audio FXB-18 D4 18″ · dual 4 Ω
Sky High Car Audio FXXL-18 D1 18″ · dual 1 Ω
Sky High Car Audio FXXL-18 D2 18″ · dual 2 Ω

Similar 18″ subwoofers from other brands

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

Fi Audio HT-1 18 S4 4.27 ft³ sealed · 5.54 ft³ ported
Fi Audio HT-1 18 S2 4.27 ft³ sealed · 5.54 ft³ ported
Sundown Audio Xv1-18 D2 4.10 ft³ sealed · 5.33 ft³ ported
Dayton Audio UMII18-22 4.17 ft³ sealed · 5.44 ft³ ported
Fi Audio HT-3 18 S2 3.21 ft³ sealed · 5.54 ft³ ported
Fi Audio HT-3 18 S4 3.21 ft³ sealed · 5.54 ft³ ported

FAQ

What box does the Sky High Car Audio BMX-18 D2 need?

Recommended net volume: 4.45 ft³ sealed, 5.76 ft³ ported tuned to 30 Hz — for one sub in a sedan at 2,500 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 BMX-18 D2 Thiele/Small specs?

Fs 20.5 Hz, Qts 0.51, Vas 7.60 ft³, Xmax 1.26″, Sd 194.9 in².

What is the Sky High Car Audio BMX-18 D2 mounting depth?

Mounting depth is 11 7/16″, cutout diameter 16 5/8″. The inside depth of the box must exceed the mounting depth by at least 1″.

How much power does the Sky High Car Audio BMX-18 D2 handle and how do I wire it?

RMS power rating: 2,500 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.