The Studiomaster Professional SX 421 is a high-Precision 2-Way Stereo, 3-Way Mono Crossover
| Input Impedance | 10K Ω Unbalance/20K Ω Balance |
| Output Level/Impedance | 0.775V, Max 7V Balanced |
| S/N ratio | >100 dB |
| Crossover frequency range | 45 Hz -9.5KHz |
| THD | 0.05% |
| Low Cut | -3dB@30Hz |
| Input sensitivity | 0dBu |
| Slope (Low, Mid, High | 24dB/octave |
| Subwoofer slope | - |
| Power supply | 230 V / 50 Hz |
| Dimension (W X D X H)mm | 483 x 120 x 44.5 (1U) |
| Net Weight (Kgs.) | 2.3 |