Polk Audio MM1240
12″ subwoofer · 4 Ω · 425 W RMS
The Polk Audio MM1240 is a shallow 12″ sub (4 5/8″ mounting depth): it fits behind a truck seat or in a slim box. With Qts 0.57 and EBP 56 it works both sealed and ported: sealed is tighter and smaller, ported is deeper and louder. Long excursion (Xmax 0.98″) — built for loud music and high power.
| 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, 425 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) | 31 1/2″ × 15 3/4″ × 7 1/4″ |
Ported
deeper, louder| Tuning (Fb) | 34 Hz |
|---|---|
| Port | slot 1 9/16 × 14 5/16″, 37 1/8″ long |
| Port velocity at 425 W | 46 ft/s |
| F3 (−3 dB, no cabin gain) | 34 Hz |
| Example box (outside) | 31 1/2″ × 15 3/4″ × 9 5/8″ |
Deeper: 3.11 ft³ (88 L) tuned to 30 Hz, 31 1/2″ × 15 3/4″ × 16 9/16″ 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 | 4 Ω |
| RMS power | 425 W |
| Fs | 35 Hz |
| Qts | 0.57 |
| Qes | 0.63 |
| Qms | 5.5 |
| Vas | 1.34 ft³ |
| Re | 3.25 Ω |
|---|---|
| Sd | 80.6 in² |
| Xmax | 0.98″ |
| Vd | 79.3 in³ calc. |
| Mms | 208 g calc. |
| BL | 15.4 T·m calc. |
| EBP | 56 — sealed or ported calc. |
| Sensitivity, 1 W / 1 m | 86.1 dB calc. |
Mounting dimensions
| Cutout diameter | 11″ |
|---|---|
| Mounting depth | 4 5/8″ |
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.
- Tacoma Access Cab — behind the front seats sealed box
- 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
- web.archive.org/web/20121103011346/http://www.polkaudio.com/downloads/manual/MMs
- web.archive.org/web/20101206235924/http://www.polkaudio.com/downloads/catalogs/2
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 DXi1240DVC 12″ · dual 4 Ω
- Polk Audio EX12 (EX Series II) 12″ · 4 Ω
- Polk Audio GXR124 12″ · 4 Ω
- Polk Audio MM120-4 12″ · 4 Ω
Similar 12″ subwoofers from other brands
Close in Fs, Qts and Vas — a box of similar volume will suit them.
- DL Audio Raven 12 (2+2) 1.48 ft³ sealed · 1.20 ft³ ported
- Phoenix Gold Ti312D4 (Ti3, DVC 4 ohm) 1.31 ft³ sealed · 1.27 ft³ ported
- Machete M12 D2 1.20 ft³ sealed · 1.20 ft³ ported
- Machete M12 D4 0.99 ft³ sealed · 1.20 ft³ ported
- Pride LP 12 D2 1.66 ft³ sealed · 1.24 ft³ ported
- Soundstream T7.124 1.27 ft³ sealed · 1.27 ft³ ported
All 12″ subwoofers in our database →
FAQ
What box does the Polk Audio MM1240 need?
Recommended net volume: 1.34 ft³ sealed, 1.27 ft³ ported tuned to 34 Hz — for one sub in a sedan at 425 W. Fit the box to your space and amp in the free calculator, with plans and a cut sheet.
What are the Polk Audio MM1240 Thiele/Small specs?
Fs 35 Hz, Qts 0.57, Vas 1.34 ft³, Xmax 0.98″, Sd 80.6 in².
What is the Polk Audio MM1240 mounting depth?
Mounting depth is 4 5/8″, 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 MM1240 handle and how do I wire it?
RMS power rating: 425 W. Wiring for several subs and amp power — in the wiring calculator.
Is the Polk Audio MM1240 better sealed or ported?
EBP 56: both work — sealed 1.34 ft³ is tighter and smaller, ported 1.27 ft³ tuned to 34 Hz is deeper and louder.
What port does the Polk Audio MM1240 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 425 W: 46 ft/s.
What box do two Polk Audio MM1240 subs need?
Two subs need twice the volume: 2.68 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.