Model Thirty-One
| Brand | KLH |
| Manufacturer | KLH Research & Development Corp. |
| Function | Speaker |
| Produced | 1971 |
| Country | United States |
| Form Factor | Bookshelf / Stand Mounted |
| Signal Path | Passive Hardware |
| Dimensions | 27.4 × 44.5 × 21 cm (W × H × D) |
| Weight | 22lbs |
| Treble | 1.8" Paper Cone |
| Midrange/Bass | 8" Paper Cone |
| Impedance (Nominal) | 8Ω |
| Crossover Frequency | 1.8kHz |
| Recommended Amplifier Power | >12W |
| Enclosure Type | Sealed |
| Enclosure Resonance | 60Hz |
| Finish | Walnut |
| MSRP (1971) | $94.95 (Per Pair) |