| Model ID | Mk I |
| Form Factor | Headphone - Circumaural |
| Signal Path | Passive Hardware |
| Weight | 14oz |
| Frequency Response | 20Hz-50kHz |
| Driver Type | Heil Air-Motion Transformer (AMT) |
| Type | Open-Back |
| Impedance | 32Ω |
| Sensitivity (1mW) | 35dB |
| Distortion (1kHz, 90dB) | 0.3% |
| Square Wave Rise Time (5kHz) | 15µS |
| Maximum Input | 14V |
| MSRP (1976) | $97 |
| Channels | 2 Channel |