Diamond CM312D2
12″ subwoofer · dual 2 Ω
| Source | web.archive.org · 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, 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) | Tight and punchy · 0.81 |
|---|---|
| Fc | 48 Hz |
| F3 (−3 dB, no cabin gain) | 44 Hz |
| Example box (outside) | 31 1/2″ × 15 3/4″ × 8 3/4″ |
Ported
deeper, louder| Tuning (Fb) | 34 Hz |
|---|---|
| Port | slot 1 9/16 × 14 5/16″, 39 9/16″ long |
| Port velocity at 300 W | 39 ft/s |
| F3 (−3 dB, no cabin gain) | 33 Hz |
| Example box (outside) | 21 3/4″ × 15 3/4″ × 13 3/8″ |
Deeper: 2.93 ft³ (83 L) tuned to 31 Hz, 31 1/2″ × 15 3/4″ × 15 1/8″ 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 2 Ω |
| RMS power | — |
| Fs | 38 Hz |
| Qts | 0.65 |
| Qes | 0.72 |
| Qms | 6.2 |
| Vas | 1.02 ft³ |
| Re (one coil) | 1.65 Ω |
|---|---|
| Sd | 76 in² |
| Xmax | 0.43″ |
| Vd | 32.9 in³ calc. |
| Mms | 207 g calc. |
| BL | 10.6 T·m calc. |
| EBP | 53 — sealed or ported calc. |
| Sensitivity, 1 W / 1 m | 85.4 dB calc. |
Mounting dimensions
| Cutout diameter | 11 1/8″ |
|---|---|
| Mounting depth | 6 1/4″ |
| Overall diameter | 12 3/8″ |
“≈” 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/20070830083842/http://www.diamondaudio.com/PDF/archive/CM3/C
- web.archive.org/web/20050405075111/http://www.diamondaudio.com:80/products/pdfs/
Other Diamond 12″ models
- 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
- Diamond DES122 12″ · dual 2 Ω
Similar 12″ subwoofers from other brands
Close in Fs, Qts and Vas — a box of similar volume will suit them.
- Bomber Bicho Papão 1200W 4+4 Ohm (SW12BPF1200-4+4) 1.59 ft³ sealed · 1.13 ft³ ported
- DD Audio 9512L ESP D1 1.73 ft³ sealed · 1.20 ft³ ported
- Pioneer TS-W309S4 1.73 ft³ sealed · 1.20 ft³ ported
- SPL Dynamics SW-300D2 1.73 ft³ sealed · 1.27 ft³ ported
- RE Audio SEX12 D2 v2 1.73 ft³ sealed · 1.20 ft³ ported
- CT Sounds TROPO-XL-12 D4 1.77 ft³ sealed · 1.02 ft³ ported
FAQ
What box does the Diamond CM312D2 need?
Recommended net volume: 1.73 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 CM312D2 Thiele/Small specs?
Fs 38 Hz, Qts 0.65, Vas 1.02 ft³, Xmax 0.43″, Sd 76 in².
What is the Diamond CM312D2 mounting depth?
Mounting depth is 6 1/4″, cutout diameter 11 1/8″. The inside depth of the box must exceed the mounting depth by at least 1″.