Sky High Car Audio FEX-12 D4
12″ subwoofer · dual 4 Ω · 1,250 W RMS
The Sky High Car Audio FEX-12 D4 is a 12″ subwoofer. With Qts 0.64 and EBP 49 it suits a sealed box: tight bass in a small enclosure; a ported box would need a lot of volume.
| Source | skyhighcaraudio.com · 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, 1,250 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 · 0.86 |
|---|---|
| Fc | 46 Hz |
| F3 (−3 dB, no cabin gain) | 41 Hz |
| Example box (outside) | 14 3/16″ × 14 3/16″ × 21 11/16″ |
Ported
deeper, louder| Tuning (Fb) | 34 Hz |
|---|---|
| Port | slot 1 9/16 × 14 5/16″, 37 1/8″ long |
| Port velocity at 1,250 W | 75 ft/s |
| F3 (−3 dB, no cabin gain) | 34 Hz |
| Example box (outside) | 20 11/16″ × 15 3/4″ × 14 3/16″ |
Deeper: 3.07 ft³ (87 L) tuned to 31 Hz, 31 1/2″ × 15 3/4″ × 19 5/8″ 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 4 Ω |
| RMS power | 1,250 W |
| Fs | 34.7 Hz |
| Qts | 0.64 |
| Qes | 0.714 |
| Qms | 6.6 |
| Vas | 1.42 ft³ |
| Re (one coil) | 3.29 Ω |
|---|---|
| Sd | 79.2 in² |
| Xmax | 0.75″ |
| Vd | 59.2 in³ calc. |
| Mms | 194 g calc. |
| BL | 13.9 T·m calc. |
| EBP | 49 — suits sealed calc. |
| Sensitivity, 1 W / 1 m | 85.7 dB calc. |
Mounting dimensions
| Cutout diameter | 10 7/8″ |
|---|---|
| Mounting depth | 7 1/16″ |
| Overall diameter | 12 3/8″ |
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
- 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 |
|---|---|---|---|---|---|---|
| Sky High Car Audio FEX-12 D2 | dual 2 Ω | 2.12 Ω | 0.739 | 1.42 ft³ | 1.80 ft³ | 1.27 ft³ · 34 Hz |
| Sky High Car Audio FEX-12 D4 | dual 4 Ω | 3.29 Ω | 0.714 | 1.42 ft³ | 1.80 ft³ | 1.27 ft³ · 34 Hz |
Other Sky High Car Audio 12″ models
- Sky High Car Audio BMX-12 D1 12″ · dual 1 Ω
- Sky High Car Audio BMX-12 D2 12″ · dual 2 Ω
- Sky High Car Audio FE-12 D2 12″ · dual 2 Ω
- Sky High Car Audio FE-12 D4 12″ · dual 4 Ω
- Sky High Car Audio FMX-12 D1 12″ · dual 1 Ω
- Sky High Car Audio FMX-12 D2 12″ · dual 2 Ω
- Sky High Car Audio FXB-12 D2 12″ · dual 2 Ω
- Sky High Car Audio FXB-12 D4 12″ · dual 4 Ω
- Sky High Car Audio FXXL-12 D1 12″ · dual 1 Ω
- Sky High Car Audio FXXL-12 D2 12″ · dual 2 Ω
Similar 12″ subwoofers from other brands
Close in Fs, Qts and Vas — a box of similar volume will suit them.
- Polk Audio MM1240DVC 1.84 ft³ sealed · 1.27 ft³ ported
- Quantum Audio QWX2000/12D4 1.80 ft³ sealed · 1.27 ft³ ported
- BOSS Audio CH12DVC 1.73 ft³ sealed · 1.20 ft³ ported
- Deaf Bonce Hannibal HSS-3212 D2 1.73 ft³ sealed · 1.20 ft³ ported
- Timpano TPT-T1000-12 D4 1.73 ft³ sealed · 1.20 ft³ ported
- PowerBass S-12T 1.87 ft³ sealed · 1.31 ft³ ported
- American Bass XO-1244 1.80 ft³ sealed · 1.27 ft³ ported
FAQ
What box does the Sky High Car Audio FEX-12 D4 need?
Recommended net volume: 1.80 ft³ sealed, 1.27 ft³ ported tuned to 34 Hz — for one sub in a sedan at 1,250 W. Fit the box to your space and amp in the free calculator, with plans and a cut sheet.
What are the Sky High Car Audio FEX-12 D4 Thiele/Small specs?
Fs 34.7 Hz, Qts 0.64, Vas 1.42 ft³, Xmax 0.75″, Sd 79.2 in².
What is the Sky High Car Audio FEX-12 D4 mounting depth?
Mounting depth is 7 1/16″, cutout diameter 10 7/8″. The inside depth of the box must exceed the mounting depth by at least 1″.
How much power does the Sky High Car Audio FEX-12 D4 handle and how do I wire it?
RMS power rating: 1,250 W. Dual 4 Ω voice coils: series gives 8 Ω, parallel gives 2 Ω at the amp. Wiring for several subs and amp power — in the wiring calculator.
Is the Sky High Car Audio FEX-12 D4 better sealed or ported?
EBP 49: a sealed box (1.80 ft³) suits it best — tight bass in a compact enclosure. Ported is possible (1.27 ft³, tuned to 34 Hz) but larger.
What port does the Sky High Car Audio FEX-12 D4 need?
For the 1.27 ft³ ported box tuned to 34 Hz: slot 1 9/16 × 14 5/16″, 37 1/8″ long, area 22.6 in²; or a round port Ø5 3/8″, ≈ 37 1/8″ long. Port air speed at 1,250 W: 75 ft/s.
What box do two Sky High Car Audio FEX-12 D4 subs need?
Two subs need twice the volume: 3.60 ft³ sealed, or 2.54 ft³ ported at the same 34 Hz tuning with twice the port area. One shared chamber or one per sub — whatever fits your vehicle.