Diamond M6mkII 12D2
12″ subwoofer · dual 2 Ω
The Diamond M6mkII 12D2 is a 12″ subwoofer. With Qts 0.51 and EBP 58 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 | 0 of 4 — missing: cutout, mounting depth, frame outer diameter, magnet diameter; the designer will use an estimate |
- Fs, Vas and Sd don't match the moving mass of 346 g (they give 649 g) — one of the spec sheet values is probably wrong.
Recommended box
For a sedan, one sub, 300 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) | Flat and accurate · 0.65 |
|---|---|
| Fc | 41 Hz |
| F3 (−3 dB, no cabin gain) | 47 Hz |
| Example box (outside) | 14 3/16″ × 14 3/16″ × 10 1/16″ |
Ported
deeper, louder| Tuning (Fb) | 34 Hz |
|---|---|
| Port | slot 1 9/16 × 14 5/16″, 39 9/16″ long |
| Port velocity at 300 W | 50 ft/s |
| F3 (−3 dB, no cabin gain) | 29 Hz |
| Example box (outside) | 31 1/2″ × 15 3/4″ × 9 1/2″ |
Deeper: 1.45 ft³ (41 L) tuned to 25 Hz, 31 1/2″ × 15 3/4″ × 9 11/16″ 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 | dual 2 Ω |
| RMS power | — |
| Fs | 32.4 Hz |
| Qts | 0.51 |
| Qes | 0.56 |
| Qms | 5.71 |
| Vas | 0.44 ft³ |
| Re (one coil) | 1.95 Ω |
|---|---|
| Sd | 75.8 in² |
| Xmax | 0.70″ |
| Vd | 53.1 in³ calc. |
| Mms | 649 g calc. |
| BL | 21.4 T·m calc. |
| EBP | 58 — sealed or ported calc. |
| Sensitivity, 1 W / 1 m | 80.8 dB calc. |
Mounting dimensions
| Cutout diameter | ≈ 11 1/8″ |
|---|---|
| Mounting depth | ≈ 5 7/8″ |
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
- 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 |
|---|---|---|---|---|---|---|
| Diamond M6mkII 12D2 | dual 2 Ω | 1.95 Ω | 0.56 | 0.44 ft³ | 0.71 ft³ | 1.20 ft³ · 34 Hz |
| Diamond M6mkII 12D4 | dual 4 Ω | 3 Ω | 0.57 | 1.17 ft³ | 0.81 ft³ | 1.20 ft³ · 34 Hz |
Other Diamond 12″ models
- Diamond CM312D2 12″ · dual 2 Ω
- Diamond CM312D4 12″ · dual 4 Ω
- Diamond D122 12″ · dual 2 Ω
- Diamond D124 12″ · dual 4 Ω
- Diamond D312D2 12″ · dual 2 Ω
- Diamond D312D4 12″ · dual 4 Ω
- Diamond D612D2 12″ · dual 2 Ω
- Diamond D612D4 12″ · dual 4 Ω
- Diamond D912D2 12″ · dual 2 Ω
- Diamond D912D4 12″ · dual 4 Ω
- Diamond DE122 12″ · dual 2 Ω
- Diamond DE124 12″ · dual 4 Ω
Similar 12″ subwoofers from other brands
Close in Fs, Qts and Vas — a box of similar volume will suit them.
- CT Sounds THERMO-12 D4 0.83 ft³ sealed · 1.17 ft³ ported
- Sundown Audio Zv7-12 D2 1.20 ft³ sealed · 2.12 ft³ ported
- Rockford Fosgate Power T2D212 0.78 ft³ sealed · 1.80 ft³ ported
- Sundown Audio M12 D2 1.02 ft³ sealed · 1.13 ft³ ported
- Sundown Audio Xv3-12 D2 0.90 ft³ sealed · 2.51 ft³ ported
- Sundown Audio Xv4-12 D2 1.09 ft³ sealed · 2.51 ft³ ported
FAQ
What box does the Diamond M6mkII 12D2 need?
Recommended net volume: 0.71 ft³ sealed, 1.20 ft³ ported tuned to 34 Hz — for one sub in a sedan at 300 W. Fit the box to your space and amp in the free calculator, with plans and a cut sheet.
What are the Diamond M6mkII 12D2 Thiele/Small specs?
Fs 32.4 Hz, Qts 0.51, Vas 0.44 ft³, Xmax 0.70″, Sd 75.8 in².
Is the Diamond M6mkII 12D2 better sealed or ported?
EBP 58: both work — sealed 0.71 ft³ is tighter and smaller, ported 1.20 ft³ tuned to 34 Hz is deeper and louder.
What port does the Diamond M6mkII 12D2 need?
For the 1.20 ft³ ported box tuned to 34 Hz: slot 1 9/16 × 14 5/16″, 39 9/16″ long, area 22.6 in²; or a round port Ø5 3/8″, ≈ 39 9/16″ long. Port air speed at 300 W: 50 ft/s.
What box do two Diamond M6mkII 12D2 subs need?
Two subs need twice the volume: 1.41 ft³ sealed, or 2.40 ft³ ported at the same 34 Hz tuning with twice the port area. One shared chamber or one per sub — whatever fits your vehicle.