Fi Audio SP3 Plus 12 D2
12″ subwoofer · dual 2 Ω · 2,500 W RMS
The Fi Audio SP3 Plus 12 D2 is a 12″ subwoofer. With Qts 0.23 and EBP 147 it suits a ported box: deeper and louder; sealed, the bass sounds a bit dry. Long excursion (Xmax 1.34″) — built for loud music and high power.
| 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, 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
smaller, tighter| Bass character (Qtc) | Dry and tight · 0.32 |
|---|---|
| Fc | 48 Hz |
| F3 (−3 dB, no cabin gain) | 138 Hz |
| Example box (outside) | 14 3/16″ × 14 3/16″ × 12 1/2″ |
Ported
deeper, louder| Tuning (Fb) | 34 Hz |
|---|---|
| Port | slot 3 15/16 × 14 5/16″, 53 3/8″ long |
| Port velocity at 2,500 W | 80 ft/s |
| F3 (−3 dB, no cabin gain) | 122 Hz |
| Example box (outside) | 26 5/8″ × 15 3/4″ × 21 7/8″ |
Deeper: 1.41 ft³ (40 L) tuned to 28 Hz, 20 3/16″ × 15 3/4″ × 12 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 | 12″ |
|---|---|
| Voice coils | dual 2 Ω |
| RMS power | 2,500 W |
| Fs | 35.2 Hz |
| Qts | 0.23 |
| Qes | 0.24 |
| Qms | 6.41 |
| Vas | 0.82 ft³ |
| Re (one coil) | 1.8 Ω |
|---|---|
| Sd | 74.4 in² |
| Xmax | 1.34″ |
| Vd | 99.6 in³ calc. |
| Mms | 289 g calc. |
| BL | 21.9 T·m calc. |
| EBP | 147 — suits ported calc. |
| Sensitivity, 1 W / 1 m | 88.2 dB calc. |
Mounting dimensions
| Cutout diameter | 11 1/8″ |
|---|---|
| Mounting depth | 10″ |
| Overall diameter | 12 1/2″ |
Where it fits in a vehicle
Spots from our vehicle guides where the cutout, mounting depth and recommended box fit. The spot sizes are approximate — measure your own vehicle.
- Bronco 4-door — behind the rear seat sealed and ported box
- Wrangler 4-door, hard top — behind the rear seat sealed and ported box
- Wrangler 4-door, soft top — behind the rear seat sealed and ported box
- FJ Cruiser — behind the rear seat sealed and ported box
- El Camino 1978–87 — behind the seat sealed and ported box
- Cherokee XJ — cargo area, spare moved out sealed and ported box
- Excursion — behind the third row sealed and ported box
- Mustang 2015–2023 coupe — trunk sealed and ported box
- Challenger / Charger — trunk sealed and ported box
- Club Car Precedent — under the rear seat sealed box
“≈” 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
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 |
|---|---|---|---|---|---|---|
| Fi Audio SP3 Plus 12 D1 | dual 1 Ω | 0.9 Ω | 0.24 | 0.82 ft³ | 0.94 ft³ | 2.19 ft³ · 34 Hz |
| Fi Audio SP3 Plus 12 D2 | dual 2 Ω | 1.8 Ω | 0.24 | 0.82 ft³ | 0.94 ft³ | 2.19 ft³ · 34 Hz |
Other Fi Audio 12″ models
- Fi Audio Alpha 12 S2 12″ · 2 Ω
- Fi Audio Alpha 12 S4 12″ · 4 Ω
- Fi Audio Alpha v1 12 S1 12″ · 1 Ω
- Fi Audio Alpha v1 12 S2 12″ · 2 Ω
- Fi Audio Alpha v1 12 S4 12″ · 4 Ω
- Fi Audio Alpha v2 12 S2 12″ · 2 Ω
- Fi Audio Alpha v2 12 S4 12″ · 4 Ω
- Fi Audio Alpha v2.1 12 S2 12″ · 2 Ω
- Fi Audio Alpha v2.1 12 S4 12″ · 4 Ω
- Fi Audio BL-NEO 12 D1 12″ · dual 1 Ω
- Fi Audio BL-NEO 12 D2 12″ · dual 2 Ω
- Fi Audio BL12 D1 12″ · dual 1 Ω
Similar 12″ subwoofers from other brands
Close in Fs, Qts and Vas — a box of similar volume will suit them.
- Deaf Bonce Apocalypse DB-SA302 D1 0.71 ft³ sealed · 2.26 ft³ ported
- Deaf Bonce Apocalypse DB-SA302 D2 0.71 ft³ sealed · 2.26 ft³ ported
- Edge EDX12D1-E7 0.67 ft³ sealed · 2.15 ft³ ported
- Vibe Audio BlackDeath 12 HEX D1 (BLACKDEATH12HEX-V7) 0.67 ft³ sealed · 2.15 ft³ ported
- Hifonics CX12D2 0.83 ft³ sealed · 2.33 ft³ ported
- SPL Dynamics SPL-300D2 0.81 ft³ sealed · 2.37 ft³ ported
FAQ
What box does the Fi Audio SP3 Plus 12 D2 need?
Recommended net volume: 0.94 ft³ sealed, 2.19 ft³ ported tuned to 34 Hz — for one sub in a sedan at 2,500 W. Fit the box to your space and amp in the free calculator, with plans and a cut sheet.
What are the Fi Audio SP3 Plus 12 D2 Thiele/Small specs?
Fs 35.2 Hz, Qts 0.23, Vas 0.82 ft³, Xmax 1.34″, Sd 74.4 in².
What is the Fi Audio SP3 Plus 12 D2 mounting depth?
Mounting depth is 10″, cutout diameter 11 1/8″. The inside depth of the box must exceed the mounting depth by at least 1″.
How much power does the Fi Audio SP3 Plus 12 D2 handle and how do I wire it?
RMS power rating: 2,500 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 Fi Audio SP3 Plus 12 D2 better sealed or ported?
EBP 147: a ported box (2.19 ft³, tuned to 34 Hz) suits it best — deeper and louder. Sealed (0.94 ft³) the bass is drier.
What port does the Fi Audio SP3 Plus 12 D2 need?
For the 2.19 ft³ ported box tuned to 34 Hz: slot 3 15/16 × 14 5/16″, 53 3/8″ long, area 56.4 in²; or a round port Ø8 1/2″, ≈ 53 3/8″ long. Port air speed at 2,500 W: 80 ft/s.
What box do two Fi Audio SP3 Plus 12 D2 subs need?
Two subs need twice the volume: 1.87 ft³ sealed, or 4.38 ft³ ported at the same 34 Hz tuning with twice the port area. One shared chamber or one per sub — whatever fits your vehicle.