Sica 21 S 4 PL
Thiele-Small parameters
| Nominal size | 21" |
|---|---|
| Impedance | 8 Ω |
| Fs | 34.6 Hz |
| Qts | 0.3 |
| Qes | 0.31 |
| Qms | 9.95 |
| Vas | 255 L |
| Sd | 1661.9 cm² |
| Xmax | 5.2 mm |
| Re | 5.7 Ω |
| Bl | 36.1 T·m |
| Mms | 325 g |
| Pe | 1200 W |
| Sensitivity | 98.8 dB |
Alignment hint
| EBP | 112 · ported |
|---|---|
| Sealed Vb (Qtc ≈ 0.71) | ≈ 56 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 |
|---|---|---|---|---|---|---|---|---|
| 18 Sound 21NLW9001 | 32 -2.6 | 0.31 +0.01 | 244 -11 | 14 +8.8 | 98 -0.8 | close | + | |
| Fane Colossus Prime 21XS | 35 +0.4 | 0.339 +0.04 | 266 +11 | 14 +8.8 | 97.5 -1.3 | close | + | |
| Fane Colossus Prime 21NDXL | 33 -1.6 | 0.36 +0.06 | 241 -14 | 14 +8.8 | 98 -0.8 | usable | + | |
| B&C 21DS115 | 34 -0.6 | 0.27 -0.03 | 204 -51 | 16.5 +11.3 | 99 +0.2 | usable | + | |
| Beyma 21"LEX1600/Nd | 30 -4.6 | 0.29 -0.01 | 305 +50 | 14 +8.8 | 98 -0.8 | usable | + | |
| Beyma 21QLEX1600Fe | 30 -4.6 | 0.28 -0.02 | 309 +54 | 13 +7.8 | 98 -0.8 | usable | + | |
| 18 Sound 21NLW5300 | 31 -3.6 | 0.32 +0.02 | 325 +70 | 15.3 +10.1 | 98.5 -0.3 | usable | + | |
| B&C 21SW152 | 32 -2.6 | 0.3 = | 200 -55 | 15 +9.8 | 96 -2.8 | usable | 4 Ω vs 8 Ω: amp load changes | + |
| RCF LF21N551 | 35 +0.4 | 0.33 +0.03 | 200 -55 | 15 +9.8 | 97 -1.8 | usable | + | |
| B&C 21SW115 | 33 -1.6 | 0.36 +0.06 | 278 +23 | 14 +8.8 | 97 -1.8 | usable | 4 Ω vs 8 Ω: amp load changes | + |
Compare the closest 3 against the 21 S 4 PL →
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.