JBL M121-8
Thiele-Small parameters
| Nominal size | 12" |
|---|---|
| Impedance | 8 Ω |
| Fs | 60 Hz |
| Qts | 0.235 |
| Qes | 0.25 |
| Qms | 4 |
| Vas | 70.8 L |
| Sd | 527.1 cm² |
| Xmax | 3.6 mm |
| Re | 5.2 Ω |
| Bl | 17.4 T·m |
| Mms | 38.7 g |
| Pe | 300 W |
| Sensitivity | 101.7 dB |
Alignment hint
| EBP | 240 · ported |
|---|---|
| Sealed Vb (Qtc ≈ 0.71) | ≈ 8.8 L |
EBP > 100: favours a ported (bass-reflex) alignment.
Rules of thumb from T/S parameters only. Verify against a real simulation before cutting wood.
Substitute candidates
| Driver | Fs (Hz) | Qts | Vas (L) | Xmax (mm) | Sens (dB) | Fit | Notes | Compare |
|---|---|---|---|---|---|---|---|---|
| JBL 2020 H | 60 = | 0.228 -0.01 | 65 -5.8 | 4 +0.4 | 101.9 +0.2 | close | + | |
| JBL 2020H | 60 = | 0.228 -0.01 | 65 -5.8 | 4 +0.4 | 101.9 +0.2 | close | + | |
| Electro-Voice DL12X | 56 -4 | 0.233 = | 77 +6.2 | 4.1 +0.5 | 100.7 -1 | close | + | |
| RCF MB 12N301 | 54 -6 | 0.24 +0.01 | 71 +0.2 | 4.9 +1.3 | 99.7 -2 | close | + | |
| Beyma 12MI100 | 58 -2 | 0.221 -0.01 | 64 -6.8 | 4.2 +0.6 | 100.4 -1.3 | close | + | |
| Altec ER-12L | 55 -5 | 0.236 = | 82.1 +11.3 | 3.3 -0.3 | 101.2 -0.5 | close | 200 W vs 300 W: lower power handling · Xmax 3.3 mm < 3.6 mm: lower excursion-limited SPL | + |
| Electro-Voice EVM-12L | 55 -5 | 0.232 = | 82.9 +12.1 | 3.3 -0.3 | 101.4 -0.3 | close | 200 W vs 300 W: lower power handling · Xmax 3.3 mm < 3.6 mm: lower excursion-limited SPL | + |
| Electro-Voice EVM-DL12X | 56 -4 | 0.24 +0.01 | 77.3 +6.5 | 4.1 +0.5 | 99.2 -2.5 | close | 150 W vs 300 W: lower power handling | + |
| RCF 12 CX251 | 60 = | 0.266 +0.03 | 62 -8.8 | 3.7 +0.1 | 100.6 -1.1 | close | + | |
| RCF CX 12N251 | 60 = | 0.266 +0.03 | 62 -8.8 | 3.7 +0.1 | 100.6 -1.1 | close | + |
Compare the closest 3 against the M121-8 →
Ranked on parameter similarity only (Qts, Fs, Vas, Xmax, sensitivity). Same nominal size required. A hint, not a simulation, model the swap before cutting or buying.
Used in enclosures (0)
No enclosure in the catalog uses this driver yet.