Focal Utopia Be 13 WS (SVC 4 ohm)
5″ subwoofer · 4 Ω · 75 W RMS
Fs 53.4 HzQts 0.49Vas 0.19 ft³Xmax 0.31″
The published specs don’t add up:
- Sd of 13.4 in² is unusual for a 5″ (typically 15.5–24.8 in²).
Recommended box
For a sedan, one sub, 75 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 | 0.18 ft³ (5 L) |
|---|---|
| Qtc | 0.71 |
| Fc | 76 Hz |
| F3 (−3 dB, no cabin gain) | 80 Hz |
| Example box (outside) | 8 11/16″ × 8 11/16″ × 7 13/16″ |
Ported
| Net volume | 0.35 ft³ (10 L) |
|---|---|
| Tuning (Fb) | 45 Hz |
| Port | slot 1 15/16 × 14 5/16″, 101 1/16″ long |
| Port velocity at 75 W | 12 ft/s |
| F3 (−3 dB, no cabin gain) | 41 Hz |
| Example box (outside) | 31 1/2″ × 15 3/4″ × 10 3/8″ |
The volume and tuning are the recommendation, but the port doesn’t fit this example box. Size the box and port in the designer.
Open ported box in designerThiele/Small parameters
| Fs | 53.4 Hz |
|---|---|
| Qts | 0.49 |
| Qes | 0.52 |
| Qms | 10.09 |
| Vas | 0.19 ft³ |
| Re | 3.09 Ω |
| Sd | 13.4 in² |
| Xmax | 0.31″ |
| Vd | 4.2 in³ calc. |
| Mms | 18 g calc. |
| BL | 6 T·m calc. |
| EBP | 103 — suits ported calc. |
| Sensitivity, 1 W / 1 m | 83.9 dB calc. |
General
| Size | 5″ |
|---|---|
| Voice coils | 4 Ω |
| RMS power | 75 W |
Mounting dimensions
| Cutout diameter | ≈ 5 5/16″ |
|---|---|
| Mounting depth | ≈ 2 15/16″ |
| Overall diameter | 5 7/8″ |
“≈” 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.