Fi Audio X12 S2
12″ subwoofer · 2 Ω · 400 W RMS
The Fi Audio X12 S2 is a 12″ subwoofer. With Qts 0.43 and EBP 76 it works both sealed and ported: sealed is tighter and smaller, ported is deeper and louder.
| 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, 400 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 · 0.80 |
|---|---|
| Fc | 66 Hz |
| F3 (−3 dB, no cabin gain) | 63 Hz |
| Example box (outside) | 14 3/16″ × 14 3/16″ × 10 7/16″ |
Ported
deeper, louder| Tuning (Fb) | 34 Hz |
|---|---|
| Port | slot 1 9/16 × 14 5/16″, 32 1/8″ long |
| Port velocity at 400 W | 50 ft/s |
| F3 (−3 dB, no cabin gain) | 38 Hz |
| Example box (outside) | 31 1/2″ × 15 3/4″ × 10″ |
Deeper: 2.44 ft³ (69 L) tuned to 35 Hz, 31 1/2″ × 15 3/4″ × 13 5/16″ 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 | 12″ |
|---|---|
| Voice coils | 2 Ω |
| RMS power | 400 W |
| Fs | 35.6 Hz |
| Qts | 0.43 |
| Qes | 0.47 |
| Qms | 5.58 |
| Vas | 1.79 ft³ |
| Re | 1.9 Ω |
|---|---|
| Sd | 74.6 in² |
| Xmax | 0.71″ |
| Vd | 52.8 in³ calc. |
| Mms | 129 g calc. |
| BL | 10.8 T·m calc. |
| EBP | 76 — sealed or ported calc. |
| Sensitivity, 1 W / 1 m | 88.9 dB calc. |
Mounting dimensions
| Cutout diameter | 11 1/8″ |
|---|---|
| Mounting depth | 6 1/4″ |
| 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
- Silverado / Sierra Crew Cab — under the rear seat sealed and ported box
- Spare tire well sealed 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 and ported 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 X12 S2 | 2 Ω | 1.9 Ω | 0.47 | 1.79 ft³ | 0.74 ft³ | 1.45 ft³ · 34 Hz |
| Fi Audio X12 S4 | 4 Ω | 2.9 Ω | 0.47 | 1.79 ft³ | 0.74 ft³ | 1.45 ft³ · 34 Hz |
| Fi Audio X12 D2 | dual 2 Ω | 1.4 Ω | 0.51 | 1.63 ft³ | 0.88 ft³ | 1.31 ft³ · 34 Hz |
| Fi Audio X12 D4 | dual 4 Ω | 2.8 Ω | 0.51 | 1.63 ft³ | 0.88 ft³ | 1.31 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.
- Sony XS-GTR121L 0.85 ft³ sealed · 1.41 ft³ ported
- ESX QE1224 (2x4 Ohm) 0.81 ft³ sealed · 1.52 ft³ ported
- Ground Zero GZRW 30SPL-EXTREME (2x2 Ohm) 0.71 ft³ sealed · 1.31 ft³ ported
- Orion HCCA 12D (1999) 0.71 ft³ sealed · 1.20 ft³ ported
- DC Audio Level 1 12 D2 0.67 ft³ sealed · 1.34 ft³ ported
- DC Audio Level 1 12 D4 0.67 ft³ sealed · 1.34 ft³ ported
FAQ
What box does the Fi Audio X12 S2 need?
Recommended net volume: 0.74 ft³ sealed, 1.45 ft³ ported tuned to 34 Hz — for one sub in a sedan at 400 W. Fit the box to your space and amp in the free calculator, with plans and a cut sheet.
What are the Fi Audio X12 S2 Thiele/Small specs?
Fs 35.6 Hz, Qts 0.43, Vas 1.79 ft³, Xmax 0.71″, Sd 74.6 in².
What is the Fi Audio X12 S2 mounting depth?
Mounting depth is 6 1/4″, 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 X12 S2 handle and how do I wire it?
RMS power rating: 400 W. Wiring for several subs and amp power — in the wiring calculator.
Is the Fi Audio X12 S2 better sealed or ported?
EBP 76: both work — sealed 0.74 ft³ is tighter and smaller, ported 1.45 ft³ tuned to 34 Hz is deeper and louder.
What port does the Fi Audio X12 S2 need?
For the 1.45 ft³ ported box tuned to 34 Hz: slot 1 9/16 × 14 5/16″, 32 1/8″ long, area 22.6 in²; or a round port Ø5 3/8″, ≈ 32 1/8″ long. Port air speed at 400 W: 50 ft/s.
What box do two Fi Audio X12 S2 subs need?
Two subs need twice the volume: 1.48 ft³ sealed, or 2.90 ft³ ported at the same 34 Hz tuning with twice the port area. One shared chamber or one per sub — whatever fits your vehicle.