The AKG K612 Pro is 120Ω at 91.8 dB/mW; the AKG K7XX (Drop) is 62Ω at 93.0 dB (no figure from the maker at all). This page is only about what they ask of an amplifier — not how they sound, which no specification on either sheet can tell you.
The K612 Pro needs 1.2 dB more than the K7XX (Drop) to reach the same loudness — 6.6 mW against 5.0 mW.
| Specification | K612 Pro | K7XX (Drop) |
|---|---|---|
| Impedance | 120 Ω | 62 Ω |
| Sensitivity | 91.8 dB/mW | 93.0 dB |
| Sensitivity (voltage) | 101.0 dB/V | 105.1 dB/V |
| Power for 100 dB | 6.6 mW | 5.0 mW |
| Voltage for 100 dB | 0.89 V | 0.56 V |
| Current for 100 dB | 7.4 mA | 9.0 mA |
| Highest source impedance that leaves them alone (one-eighth rule) | 15.00 Ω | 7.75 Ω |
| Sources that reach 100 dB out of 280 | 277 | 280 |
One caution before reading the rows. For AKG K7XX (Drop) the maker publishes no sensitivity figure at all. The number in the table was collected when this database was first built and has never been traced to a manufacturer document, so treat every row below it as an estimate rather than a specification.
3 of the 280 sources have the power for the K7XX (Drop) but not for the K612 Pro — Apple USB-C dongle (EU), Steinberg UR22C, Sony NW-A306.
17 sources are low enough in output impedance for the K612 Pro under the one-eighth rule but not for the K7XX (Drop) (Zoom AMS-22, Arturia MiniFuse 2, Arturia MiniFuse 1, 14 more).
277 of the 280 sources here reach 100 dB on both. That count is about power only — the output-impedance and hiss lines above are separate questions, and a source can pass this one and fail those.
Each model has a page of its own with the full source list, the hiss estimate and the provenance of every figure above: AKG K612 Pro and AKG K7XX (Drop). Each figure on this page is labelled on those pages with where it came from, including the ones AKG never published — what that maker publishes, counted.