Polk Audio DXi1240DVC
12″ subwoofer · dual 4 Ω · 360 W RMS
The Polk Audio DXi1240DVC is a 12″ subwoofer. With Qts 0.49 and EBP 56 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 | 2 of 4 — missing: frame outer diameter, magnet diameter; the designer will use an estimate |
Recommended box
For a sedan, one sub, 360 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 | 49 Hz |
| F3 (−3 dB, no cabin gain) | 46 Hz |
| Example box (outside) | 14 3/16″ × 14 3/16″ × 19 13/16″ |
Ported
deeper, louder| Tuning (Fb) | 33 Hz |
|---|---|
| Port | slot 1 9/16 × 14 5/16″, 21 13/16″ long |
| Port velocity at 360 W | 57 ft/s |
| F3 (−3 dB, no cabin gain) | 32 Hz |
| Example box (outside) | 31 1/2″ × 15 3/4″ × 12″ |
Deeper: 3.11 ft³ (88 L) tuned to 32 Hz, 31 1/2″ × 15 3/4″ × 15 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 | 360 W |
| Fs | 30 Hz |
| Qts | 0.49 |
| Qes | 0.534 |
| Qms | 6 |
| Vas | 2.68 ft³ |
| Re (one coil) | 3.5 Ω |
|---|---|
| Sd | 80.6 in² |
| Xmax | 0.71″ |
| Vd | 57.1 in³ calc. |
| Mms | 142 g calc. |
| BL | 13.2 T·m calc. |
| EBP | 56 — sealed or ported calc. |
| Sensitivity, 1 W / 1 m | 87.9 dB calc. |
Mounting dimensions
| Cutout diameter | 11″ |
|---|---|
| Mounting depth | 6 1/4″ |
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 box
Only Qts is published — Qms assumed to be 6 and Qes calculated (barely affects box design).
“≈” 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 Polk Audio 12″ models
- Polk Audio db124 12″ · 4 Ω
- Polk Audio db124DVC 12″ · dual 4 Ω
- Polk Audio db1240 12″ · 4 Ω
- Polk Audio db1240DVC 12″ · dual 4 Ω
- Polk Audio dX12-4 12″ · 4 Ω
- Polk Audio dX12-8 12″ · 8 Ω
- Polk Audio DXi124 DVC 12″ · dual 4 Ω
- Polk Audio DXi124 SVC 12″ · 4 Ω
- Polk Audio EX12 (EX Series II) 12″ · 4 Ω
- Polk Audio GXR124 12″ · 4 Ω
- Polk Audio MM120-4 12″ · 4 Ω
- Polk Audio MM124 (Polk/MOMO) 12″ · 4 Ω
Similar 12″ subwoofers from other brands
Close in Fs, Qts and Vas — a box of similar volume will suit them.
- Infinity Primus 1270 1.59 ft³ sealed · 2.15 ft³ ported
- Hertz Energy ES 300 (SVC 4 ohm) 1.80 ft³ sealed · 2.08 ft³ ported
- Alpine SWA-12S4 (Atom) 1.48 ft³ sealed · 1.91 ft³ ported
- Machete MS-12 D2 1.73 ft³ sealed · 2.26 ft³ ported
- SPL Dynamics V-300S4 1.31 ft³ sealed · 2.01 ft³ ported
- Blaupunkt BPW-E12S (SVC 4 ohm) 1.73 ft³ sealed · 2.26 ft³ ported
FAQ
What box does the Polk Audio DXi1240DVC need?
Recommended net volume: 1.62 ft³ sealed, 2.15 ft³ ported tuned to 33 Hz — for one sub in a sedan at 360 W. Fit the box to your space and amp in the free calculator, with plans and a cut sheet.
What are the Polk Audio DXi1240DVC Thiele/Small specs?
Fs 30 Hz, Qts 0.49, Vas 2.68 ft³, Xmax 0.71″, Sd 80.6 in².
What is the Polk Audio DXi1240DVC mounting depth?
Mounting depth is 6 1/4″, cutout diameter 11″. The inside depth of the box must exceed the mounting depth by at least 1″.
How much power does the Polk Audio DXi1240DVC handle and how do I wire it?
RMS power rating: 360 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 Polk Audio DXi1240DVC better sealed or ported?
EBP 56: both work — sealed 1.62 ft³ is tighter and smaller, ported 2.15 ft³ tuned to 33 Hz is deeper and louder.
What port does the Polk Audio DXi1240DVC need?
For the 2.15 ft³ ported box tuned to 33 Hz: slot 1 9/16 × 14 5/16″, 21 13/16″ long, area 22.6 in²; or a round port Ø5 3/8″, ≈ 21 13/16″ long. Port air speed at 360 W: 57 ft/s.
What box do two Polk Audio DXi1240DVC subs need?
Two subs need twice the volume: 3.25 ft³ sealed, or 4.31 ft³ ported at the same 33 Hz tuning with twice the port area. One shared chamber or one per sub — whatever fits your vehicle.