Sundown Audio Xv1-18 D4
18″ subwoofer · dual 4 Ω · 1,250 W RMS
| Source | web.archive.org · 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, 1,250 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) | Boomy, with a bump · 0.99 |
|---|---|
| Fc | 37 Hz |
| F3 (−3 dB, no cabin gain) | 31 Hz |
| Example box (outside) | 31 1/2″ × 20 1/2″ × 14 5/8″ |
Ported
deeper, louder| Tuning (Fb) | 30 Hz |
|---|---|
| Port | slot 2 3/4 × 19 1/16″, 23 7/16″ long |
| Port velocity at 1,250 W | 64 ft/s |
| F3 (−3 dB, no cabin gain) | 27 Hz |
| Example box (outside) | 31 1/2″ × 20 1/2″ × 20 3/4″ |
Deeper: 6.96 ft³ (197 L) tuned to 28 Hz, 31 1/2″ × 20 1/2″ × 26 3/8″ 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 4 Ω |
| RMS power | 1,250 W |
| Fs | 22.5 Hz |
| Qts | 0.60 |
| Qes | 0.67 |
| Qms | 5.49 |
| Vas | 7.27 ft³ |
| Re (one coil) | 3.05 Ω |
|---|---|
| Sd | 179.4 in² |
| Xmax | 1.18″ |
| Vd | 211.9 in³ calc. |
| Mms | 461 g calc. |
| BL | 17.2 T·m calc. |
| EBP | 34 — suits sealed calc. |
| Sensitivity, 1 W / 1 m | 87.4 dB calc. |
Mounting dimensions
| Cutout diameter | 16 11/16″ |
|---|---|
| Mounting depth | 10 1/4″ |
| Overall diameter | 18 7/16″ |
Cone area (Sd) calculated from Fs, Vas and Mms: 179.4 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
- web.archive.org/web/20190807034628/http://sundownaudio.com/index.php/products/di
- web.archive.org/web/20210125011608/https://sundownaudio.com/lv/sa/discontinued/d
Other Sundown Audio 18″ models
- Sundown Audio Inhuman-18 D1 18″ · dual 1 Ω
- Sundown Audio M18 D1 18″ · dual 1 Ω
- Sundown Audio M18 D2 18″ · dual 2 Ω
- Sundown Audio NSv1-18 D1 18″ · dual 1 Ω
- Sundown Audio NSv2-18 D2 18″ · dual 2 Ω
- Sundown Audio NSv4-18 D1 18″ · dual 1 Ω
- Sundown Audio NSv4-18 D2 18″ · dual 2 Ω
- Sundown Audio NSv5-18 D1 18″ · dual 1 Ω
- Sundown Audio NSv5-18 D2 18″ · dual 2 Ω
- Sundown Audio NSv6-18 D1 18″ · dual 1 Ω
- Sundown Audio NSv6-18 D2 18″ · dual 2 Ω
- Sundown Audio SAv2-18 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.
- Sky High Car Audio BMX-18 D1 4.45 ft³ sealed · 5.01 ft³ ported
- Sky High Car Audio FMX-18 D1 4.45 ft³ sealed · 5.16 ft³ ported
- Fi Audio HT-1 18 S2 4.27 ft³ sealed · 5.54 ft³ ported
- PSI Platform 2 18 4.34 ft³ sealed · 5.65 ft³ ported
- Dayton Audio UMII18-22 4.17 ft³ sealed · 5.44 ft³ ported
- Fi Audio HT-1 18 S4 4.27 ft³ sealed · 5.54 ft³ ported
FAQ
What box does the Sundown Audio Xv1-18 D4 need?
Recommended net volume: 4.10 ft³ sealed, 5.30 ft³ ported tuned to 30 Hz — for one sub in a sedan at 1,250 W. Fit the box to your space and amp in the free calculator, with plans and a cut sheet.
What are the Sundown Audio Xv1-18 D4 Thiele/Small specs?
Fs 22.5 Hz, Qts 0.60, Vas 7.27 ft³, Xmax 1.18″, Sd 179.4 in².
What is the Sundown Audio Xv1-18 D4 mounting depth?
Mounting depth is 10 1/4″, cutout diameter 16 11/16″. The inside depth of the box must exceed the mounting depth by at least 1″.
How much power does the Sundown Audio Xv1-18 D4 handle and how do I wire it?
RMS power rating: 1,250 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.