Sky High Car Audio FXXL-18 D2
18″ subwoofer · dual 2 Ω · 5,000 W RMS
| 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, 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| Bass character (Qtc) | Tight and punchy · 0.80 |
|---|---|
| Fc | 44 Hz |
| F3 (−3 dB, no cabin gain) | 41 Hz |
| Example box (outside) | 19 11/16″ × 19 11/16″ × 18 1/4″ |
Ported
deeper, louder| Tuning (Fb) | 31 Hz |
|---|---|
| Port | slot 3 15/16 × 19 1/16″, 57 1/16″ long |
| Port velocity at 5,000 W | 72 ft/s |
| F3 (−3 dB, no cabin gain) | 31 Hz |
| Example box (outside) | 31 1/2″ × 20 1/2″ × 20 9/16″ |
Deeper: 6.96 ft³ (197 L) tuned to 27 Hz, 31 1/2″ × 20 1/2″ × 34 1/16″ outside — a bigger box with flatter deep bass. Open in the calculator
Projects with this subwoofer
Boxes that users designed and published: plans, cut sheet and response graph.
Thiele/Small parameters
| Size | 18″ |
|---|---|
| Voice coils | dual 2 Ω |
| RMS power | 5,000 W |
| Fs | 28.4 Hz |
| Qts | 0.52 |
| Qes | 0.581 |
| Qms | 5 |
| Vas | 4.05 ft³ |
| Re (one coil) | 1.29 Ω |
|---|---|
| Sd | 179.7 in² |
| Xmax | 1.42″ |
| Vd | 254.7 in³ calc. |
| Mms | 521 g calc. |
| BL | 14.4 T·m calc. |
| EBP | 49 — suits sealed calc. |
| Sensitivity, 1 W / 1 m | 88.6 dB calc. |
Mounting dimensions
| Cutout diameter | 16 5/8″ |
|---|---|
| Mounting depth | 12 3/16″ |
| Overall diameter | 18 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 18″ models
- Sky High Car Audio BMX-18 D1 18″ · dual 1 Ω
- Sky High Car Audio BMX-18 D2 18″ · dual 2 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
Similar 18″ subwoofers from other brands
Close in Fs, Qts and Vas — a box of similar volume will suit them.
- Sundown Audio Xv3-18 D2 3.28 ft³ sealed · 6.99 ft³ ported
- Sundown Audio Uv2-18 D2 2.79 ft³ sealed · 4.03 ft³ ported
- Fi Audio NEO 4.7 18 D1 2.79 ft³ sealed · 3.57 ft³ ported
- Fi Audio NEO 4.7 18 D2 2.79 ft³ sealed · 3.57 ft³ ported
- Magnum MEW 18-22DC 2.14 ft³ sealed · 3.14 ft³ ported
- Skar Audio ZVX-18v2 D2 3.43 ft³ sealed · 5.26 ft³ ported
FAQ
What box does the Sky High Car Audio FXXL-18 D2 need?
Recommended net volume: 2.97 ft³ sealed, 3.25 ft³ ported tuned to 31 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-18 D2 Thiele/Small specs?
Fs 28.4 Hz, Qts 0.52, Vas 4.05 ft³, Xmax 1.42″, Sd 179.7 in².
What is the Sky High Car Audio FXXL-18 D2 mounting depth?
Mounting depth is 12 3/16″, 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 FXXL-18 D2 handle and how do I wire it?
RMS power rating: 5,000 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.