DD Audio 9918b ESP D2
18″ subwoofer · dual 2 Ω · 2,500 W RMS
Fs 26.2 HzQts 0.42Vas 5.72 ft³Xmax 0.87″
The published specs don’t add up:
- The spec sheet's Qts 0.4705 doesn't match its Qes and Qms (they give 0.42).
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
| Net volume | 2.31 ft³ (65.5 L) |
|---|---|
| Qtc | 0.78 |
| Fc | 49 Hz |
| F3 (−3 dB, no cabin gain) | 47 Hz |
| Example box (outside) | 20 1/16″ × 20 1/16″ × 14 5/16″ |
Ported
| Net volume | 6.99 ft³ (198 L) |
|---|---|
| Tuning (Fb) | 27 Hz |
| Port | slot 4 3/4 × 19 7/16″, 40 1/4″ long |
| Port velocity at 2,500 W | 63 ft/s |
| F3 (−3 dB, no cabin gain) | 25 Hz |
| Example box (outside) | 31 1/2″ × 20 7/8″ × 29 15/16″ |
Thiele/Small parameters
| Fs | 26.2 Hz |
|---|---|
| Qts | 0.42 |
| Qes | 0.517 |
| Qms | 2.27 |
| Vas | 5.72 ft³ |
| Re (one coil) | ≈ 1.7 Ω |
| Sd | ≈ 180.6 in² |
| Xmax | 0.87″ |
| EBP | 51 — sealed or ported calc. |
| Sensitivity, 1 W / 1 m | 89.5 dB calc. |
General
| Size | 18″ |
|---|---|
| Voice coils | dual 2 Ω |
| RMS power | 2,500 W |
Mounting dimensions
| Cutout diameter | 16 3/4″ |
|---|---|
| Mounting depth | 11 7/8″ |
| Overall diameter | 18 1/4″ |
“≈” 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 DD Audio 18″ models
- DD Audio 818f D1 18″ · dual 1 Ω
- DD Audio 818f D2 18″ · dual 2 Ω
- DD Audio 3518i ESP D2 18″ · dual 2 Ω
- DD Audio 9518L ESP D1 18″ · dual 1 Ω
- DD Audio 9918c D1 18″ · dual 1 Ω
- DD Audio 9918c D2 18″ · dual 2 Ω