Sundown Audio Xv1-18 D2
18″ subwoofer · dual 2 Ω · 1,250 W RMS
The Sundown Audio Xv1-18 D2 is a 18″ subwoofer. With Qts 0.49 and EBP 39 it suits a sealed box: tight bass in a small enclosure; a ported box would need a lot of volume.
| 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) | Tight and punchy · 0.84 |
|---|---|
| Fc | 37 Hz |
| F3 (−3 dB, no cabin gain) | 34 Hz |
| Example box (outside) | 31 1/2″ × 20 1/2″ × 14 5/8″ |
Ported
deeper, louder| Tuning (Fb) | 30 Hz |
|---|---|
| Port | slot 2 15/16 × 19 1/16″, 25 1/8″ 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″ × 21 1/4″ |
Deeper: 6.96 ft³ (197 L) tuned to 27 Hz, 31 1/2″ × 20 1/2″ × 26 11/16″ 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 | 1,250 W |
| Fs | 21.6 Hz |
| Qts | 0.49 |
| Qes | 0.55 |
| Qms | 4.85 |
| Vas | 7.84 ft³ |
| Re (one coil) | 1.9 Ω |
|---|---|
| Sd | 179.8 in² |
| Xmax | 1.18″ |
| Vd | 212.3 in³ calc. |
| Mms | 466 g calc. |
| BL | 14.8 T·m calc. |
| EBP | 39 — suits sealed calc. |
| Sensitivity, 1 W / 1 m | 88.1 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: 179.8 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
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 |
|---|---|---|---|---|---|---|
| Sundown Audio Xv1-18 D2 | dual 2 Ω | 1.9 Ω | 0.55 | 7.84 ft³ | 4.10 ft³ | 5.33 ft³ · 30 Hz |
| Sundown Audio Xv1-18 D4 | dual 4 Ω | 3.05 Ω | 0.67 | 7.27 ft³ | 4.10 ft³ | 5.30 ft³ · 30 Hz |
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.
- Fi Audio HT-1 18 S4 4.27 ft³ sealed · 5.54 ft³ ported
- Sky High Car Audio BMX-18 D2 4.45 ft³ sealed · 5.76 ft³ ported
- Sky High Car Audio FMX-18 D2 4.45 ft³ sealed · 5.76 ft³ ported
- Fi Audio HT-1 18 S2 4.27 ft³ sealed · 5.54 ft³ ported
- Dayton Audio UMII18-22 4.17 ft³ sealed · 5.44 ft³ ported
- Fi Audio HT-3 18 S4 3.21 ft³ sealed · 5.54 ft³ ported
FAQ
What box does the Sundown Audio Xv1-18 D2 need?
Recommended net volume: 4.10 ft³ sealed, 5.33 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 D2 Thiele/Small specs?
Fs 21.6 Hz, Qts 0.49, Vas 7.84 ft³, Xmax 1.18″, Sd 179.8 in².
What is the Sundown Audio Xv1-18 D2 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 D2 handle and how do I wire it?
RMS power rating: 1,250 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.
Is the Sundown Audio Xv1-18 D2 better sealed or ported?
EBP 39: a sealed box (4.10 ft³) suits it best — tight bass in a compact enclosure. Ported is possible (5.33 ft³, tuned to 30 Hz) but larger.
What port does the Sundown Audio Xv1-18 D2 need?
For the 5.33 ft³ ported box tuned to 30 Hz: slot 2 15/16 × 19 1/16″, 25 1/8″ long, area 56.3 in²; or a round port Ø8 7/16″, ≈ 25 1/8″ long. Port air speed at 1,250 W: 64 ft/s.
What box do two Sundown Audio Xv1-18 D2 subs need?
Two subs need twice the volume: 8.19 ft³ sealed, or 10.67 ft³ ported at the same 30 Hz tuning with twice the port area. One shared chamber or one per sub — whatever fits your vehicle.