SoundQubed HDS3.218 D4
18″ subwoofer · dual 4 Ω · 1,200 W RMS
Fs 29.6 HzQts 0.63Vas 3.53 ft³Xmax 1.18″
The published specs don’t add up:
- The published Xmax 1.18″ looks like max (mechanical) excursion, not linear: the excursion-limited power will read too high.
Recommended box
For a sedan, one sub, 1,200 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
| Net volume | 3.71 ft³ (105 L) |
|---|---|
| Qtc | 0.89 |
| Fc | 41 Hz |
| F3 (−3 dB, no cabin gain) | 36 Hz |
| Example box (outside) | 31 1/2″ × 20 7/8″ × 13 3/16″ |
Ported
| Net volume | 6.32 ft³ (179 L) |
|---|---|
| Tuning (Fb) | 29 Hz |
| Port | slot 3 3/8 × 19 7/16″, 26 1/16″ long |
| Port velocity at 1,200 W | 65 ft/s |
| F3 (−3 dB, no cabin gain) | 25 Hz |
| Example box (outside) | 31 1/2″ × 20 7/8″ × 24 1/4″ |
Thiele/Small parameters
| Fs | 29.6 Hz |
|---|---|
| Qts | 0.63 |
| Qes | 0.702 |
| Qms | 6.61 |
| Vas | 3.53 ft³ |
| Re (one coil) | ≈ 3.4 Ω |
| Sd | 163.3 in² |
| Xmax | 1.18″ |
| Vd | 192.8 in³ calc. |
| Mms | 455 g calc. |
| BL | 20.2 T·m calc. |
| EBP | 42 — suits sealed calc. |
| Sensitivity, 1 W / 1 m | 87.7 dB calc. |
General
| Size | 18″ |
|---|---|
| Voice coils | dual 4 Ω |
| RMS power | 1,200 W |
Mounting dimensions
| Cutout diameter | 16 3/4″ |
|---|---|
| Mounting depth | 9″ |
| Overall diameter | 18 1/2″ |
Cone area (Sd) calculated from Fs, Vas and Mms: 163.3 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
Other SoundQubed 18″ models
- SoundQubed HDS3.218 D2 18″ · dual 2 Ω
- SoundQubed HDX318 D1 18″ · dual 1 Ω
- SoundQubed HDX318 D2 18″ · dual 2 Ω
- SoundQubed HDX418 D1 18″ · dual 1 Ω