Sigma II
| Brand | STR |
| Manufacturer | Sound Technology Research |
| Function | Speaker |
| Produced | 1975 |
| Country | United States |
| Form Factor | Floorstanding |
| Signal Path | Analog Hardware |
| Dimensions | 40.4 × 80.6 × 39.4 cm (W × H × D) |
| Weight | 85lbs |
| Frequency Response | 30Hz-23kHz ±5dB, 40Hz-21kHz ±4dB |
| Treble | 3" Paper Cone (Phenolic Ring, CTS) |
| Treble (Rear) | Piezo |
| Midrange | 4.5" Paper Cone |
| Bass | 12" Paper Cone |
| Sensitivity | 94dB/W/m |
| Impedance (Nominal) | 8Ω |
| Crossover Frequencies | 900Hz, 5kHz |
| Recommended Amplifier Power | 15-200W |
| Power Handling | 200W |
| Enclosure Type | Bass Reflex |
| Finish | Walnut |
| MSRP (1975) | $399 |