SD-21
| Brand | Scan-Speak |
| Manufacturer | Dantax |
| Function | Speaker |
| Produced | 1985 |
| Country | Denmark |
| Model ID | SD 21 |
| Form Factor | Floorstanding |
| Signal Path | Passive Hardware |
| Dimensions | 30 × 67.9 × 27.3 cm (W × H × D) |
| Weight | 18.3kg |
| Frequency Response | 38Hz-22kHz |
| Treble | 2.5cm Dome |
| Midrange | 10cm Cone |
| Bass | 21cm Cone |
| Sensitivity (96dB/1m) | 2.5W |
| Impedance (Nominal) | 8Ω |
| Power Handling | 100W |
| Power Handling (Music) | 150W |
| Enclosure Type | Sealed |
| Finish | Walnut |
| MSRP (1985) | 2995 kr |