Sky High Car Audio FE-15 D4
15″ subwoofer · dual 4 Ω · 700 W RMS
The Sky High Car Audio FE-15 D4 is a 15″ subwoofer. With Qts 1.07 and EBP 25 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, 700 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) | Boomy, with a bump · 1.53 |
|---|---|
| Fc | 46 Hz |
| F3 (−3 dB, no cabin gain) | 33 Hz |
| Example box (outside) | 31 1/2″ × 17 11/16″ × 11 7/8″ |
Ported
deeper, louder| Tuning (Fb) | 34 Hz |
|---|---|
| Port | slot 1 9/16 × 16 5/16″, 20 7/8″ long |
| Port velocity at 700 W | 53 ft/s |
| F3 (−3 dB, no cabin gain) | 33 Hz |
| Example box (outside) | 31 1/2″ × 17 11/16″ × 11 7/8″ |
Deeper: 4.73 ft³ (134 L) tuned to 36 Hz, 31 1/2″ × 17 11/16″ × 20 1/16″ 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 | 15″ |
|---|---|
| Voice coils | dual 4 Ω |
| RMS power | 700 W |
| Fs | 31.8 Hz |
| Qts | 1.07 |
| Qes | 1.29 |
| Qms | 6.11 |
| Vas | 2.96 ft³ |
| Re (one coil) | 3.2 Ω |
|---|---|
| Sd | 122.4 in² |
| Xmax | 0.59″ |
| Vd | 72.3 in³ calc. |
| Mms | 264 g calc. |
| BL | 11.4 T·m calc. |
| EBP | 25 — suits sealed calc. |
| Sensitivity, 1 W / 1 m | 85.2 dB calc. |
Mounting dimensions
| Cutout diameter | 13 9/16″ |
|---|---|
| Mounting depth | 8 1/16″ |
| Overall diameter | 15 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.
- Excursion — behind the third row sealed and ported box
Cone area (Sd) calculated from Fs, Vas and Mms: 122.3 in².
“≈” 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 FE-15 D2 | dual 2 Ω | 1.95 Ω | 1.03 | 2.92 ft³ | 2.79 ft³ | 2.33 ft³ · 33 Hz |
| Sky High Car Audio FE-15 D4 | dual 4 Ω | 3.2 Ω | 1.29 | 2.96 ft³ | 2.79 ft³ | 2.37 ft³ · 34 Hz |
Other Sky High Car Audio 15″ models
- Sky High Car Audio BMX-15 D1 15″ · dual 1 Ω
- Sky High Car Audio BMX-15 D2 15″ · dual 2 Ω
- Sky High Car Audio FEX-15 D2 15″ · dual 2 Ω
- Sky High Car Audio FEX-15 D4 15″ · dual 4 Ω
- Sky High Car Audio FMX-15 D1 15″ · dual 1 Ω
- Sky High Car Audio FMX-15 D2 15″ · dual 2 Ω
- Sky High Car Audio FXB-15 D2 15″ · dual 2 Ω
- Sky High Car Audio FXB-15 D4 15″ · dual 4 Ω
- Sky High Car Audio FXXL-15 D1 15″ · dual 1 Ω
- Sky High Car Audio FXXL-15 D2 15″ · dual 2 Ω
Similar 15″ subwoofers from other brands
Close in Fs, Qts and Vas — a box of similar volume will suit them.
- Lanzar OPTI1522D 2.83 ft³ sealed · 2.26 ft³ ported
- Timpano TPT-T2500-15 D4 2.83 ft³ sealed · 1.98 ft³ ported
- Kicx PRO-382 (2+2) 2.83 ft³ sealed · 2.51 ft³ ported
- Hertz Energy ES 380.5 (SVC 4 ohm) 2.86 ft³ sealed · 2.79 ft³ ported
- DL Audio Gryphon Lite 15 V.3 (2+2) 2.83 ft³ sealed · 2.58 ft³ ported
- DL Audio Gryphon Lite 15 V.3 SE (2+2) 2.83 ft³ sealed · 2.58 ft³ ported
FAQ
What box does the Sky High Car Audio FE-15 D4 need?
Recommended net volume: 2.79 ft³ sealed, 2.37 ft³ ported tuned to 34 Hz — for one sub in a sedan at 700 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 FE-15 D4 Thiele/Small specs?
Fs 31.8 Hz, Qts 1.07, Vas 2.96 ft³, Xmax 0.59″, Sd 122.4 in².
What is the Sky High Car Audio FE-15 D4 mounting depth?
Mounting depth is 8 1/16″, cutout diameter 13 9/16″. The inside depth of the box must exceed the mounting depth by at least 1″.
How much power does the Sky High Car Audio FE-15 D4 handle and how do I wire it?
RMS power rating: 700 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 FE-15 D4 better sealed or ported?
EBP 25: a sealed box (2.79 ft³) suits it best — tight bass in a compact enclosure. Ported is possible (2.37 ft³, tuned to 34 Hz) but larger.
What port does the Sky High Car Audio FE-15 D4 need?
For the 2.37 ft³ ported box tuned to 34 Hz: slot 1 9/16 × 16 5/16″, 20 7/8″ long, area 25.7 in²; or a round port Ø5 11/16″, ≈ 20 7/8″ long. Port air speed at 700 W: 53 ft/s.
What box do two Sky High Car Audio FE-15 D4 subs need?
Two subs need twice the volume: 5.58 ft³ sealed, or 4.73 ft³ ported at the same 34 Hz tuning with twice the port area. One shared chamber or one per sub — whatever fits your vehicle.