Sky High Car Audio BMX-18 D1
18″ subwoofer · dual 1 Ω · 2,500 W RMS
The Sky High Car Audio BMX-18 D1 is a 18″ subwoofer. With Qts 0.60 and EBP 34 it suits a sealed box: tight bass in a small enclosure; a ported box would need a lot of volume. Long excursion (Xmax 1.26″) — built for loud music and high power.
| 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| Bass character (Qtc) | Tight and punchy · 0.94 |
|---|---|
| Fc | 35 Hz |
| F3 (−3 dB, no cabin gain) | 30 Hz |
| Example box (outside) | 31 1/2″ × 20 1/2″ × 15 11/16″ |
Ported
deeper, louder| Tuning (Fb) | 30 Hz |
|---|---|
| Port | slot 3 15/16 × 19 1/16″, 37 1/4″ long |
| Port velocity at 2,500 W | 64 ft/s |
| F3 (−3 dB, no cabin gain) | 27 Hz |
| Example box (outside) | 31 1/2″ × 20 1/2″ × 22 15/16″ |
Deeper: 7.56 ft³ (214 L) tuned to 26 Hz, 31 1/2″ × 20 1/2″ × 31 7/8″ 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 1 Ω |
| RMS power | 2,500 W |
| Fs | 22.7 Hz |
| Qts | 0.60 |
| Qes | 0.674 |
| Qms | 5.67 |
| Vas | 6.28 ft³ |
| Re (one coil) | 1.16 Ω |
|---|---|
| Sd | 194.9 in² |
| Xmax | 1.26″ |
| Vd | 245.5 in³ calc. |
| Mms | 620 g calc. |
| BL | 12.3 T·m calc. |
| EBP | 34 — suits sealed calc. |
| Sensitivity, 1 W / 1 m | 86.9 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
Voice coil versions
The same sub with different voice coils: the parameters are nearly the same — pick by your amp and wiring.
| Model | Voice coils | Re | Qes | Vas | Sealed | Ported |
|---|---|---|---|---|---|---|
| Sky High Car Audio BMX-18 D1 | dual 1 Ω | 1.16 Ω | 0.674 | 6.28 ft³ | 4.45 ft³ | 5.01 ft³ · 30 Hz |
| Sky High Car Audio BMX-18 D2 | dual 2 Ω | 2.41 Ω | 0.564 | 7.60 ft³ | 4.45 ft³ | 5.76 ft³ · 30 Hz |
Other Sky High Car Audio 18″ models
- 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.
- Sundown Audio Xv1-18 D4 4.10 ft³ sealed · 5.30 ft³ ported
- DL Audio Phoenix Bass Machine 18 (2+2) 4.13 ft³ sealed · 4.31 ft³ ported
- Fi Audio SP4 18 D1 4.27 ft³ sealed · 4.34 ft³ ported
- Fi Audio SP418 v2.1 D1 4.27 ft³ sealed · 4.34 ft³ ported
- Fi Audio SP4 18 D2 4.27 ft³ sealed · 4.34 ft³ ported
- Fi Audio SP418 v2.1 D2 4.27 ft³ sealed · 4.34 ft³ ported
FAQ
What box does the Sky High Car Audio BMX-18 D1 need?
Recommended net volume: 4.45 ft³ sealed, 5.01 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 D1 Thiele/Small specs?
Fs 22.7 Hz, Qts 0.60, Vas 6.28 ft³, Xmax 1.26″, Sd 194.9 in².
What is the Sky High Car Audio BMX-18 D1 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 D1 handle and how do I wire it?
RMS power rating: 2,500 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.
Is the Sky High Car Audio BMX-18 D1 better sealed or ported?
EBP 34: a sealed box (4.45 ft³) suits it best — tight bass in a compact enclosure. Ported is possible (5.01 ft³, tuned to 30 Hz) but larger.
What port does the Sky High Car Audio BMX-18 D1 need?
For the 5.01 ft³ ported box tuned to 30 Hz: slot 3 15/16 × 19 1/16″, 37 1/4″ long, area 75 in²; or a round port Ø9 3/4″, ≈ 37 1/4″ long. Port air speed at 2,500 W: 64 ft/s.
What box do two Sky High Car Audio BMX-18 D1 subs need?
Two subs need twice the volume: 8.90 ft³ sealed, or 10.03 ft³ ported at the same 30 Hz tuning with twice the port area. One shared chamber or one per sub — whatever fits your vehicle.