The Sennheiser HD 6XX (Drop) is 300Ω at 97.8 dB/mW; the Sony MDR-MV1 is 24Ω at 100.0 dB/mW. 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 Sennheiser HD 6XX (Drop) needs 2.2 dB more than the Sony MDR-MV1 to reach the same loudness — 1.7 mW against 1.0 mW.
| Specification | Sennheiser HD 6XX (Drop) | Sony MDR-MV1 |
|---|---|---|
| Impedance | 300 Ω | 24 Ω |
| Sensitivity | 97.8 dB/mW | 100.0 dB/mW |
| Sensitivity (voltage) | 103.0 dB/V | 116.2 dB/V |
| Power for 100 dB | 1.7 mW | 1.0 mW |
| Voltage for 100 dB | 0.71 V | 0.15 V |
| Current for 100 dB | 2.4 mA | 6.5 mA |
| Highest source impedance that leaves them alone (one-eighth rule) | 37.50 Ω | 3.00 Ω |
| Sources that reach 100 dB out of 280 | 280 | 280 |
Every source in the database that drives one of them drives the other. On power, the choice between these two changes nothing about what amplifier you need.
20 sources are low enough in output impedance for the Sennheiser HD 6XX (Drop) under the one-eighth rule but not for the Sony MDR-MV1 (Zoom AMS-22, Arturia MiniFuse 2, Arturia MiniFuse 1, 17 more).
280 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: Sennheiser HD 6XX (Drop) and Sony MDR-MV1. Every figure on this page comes from what Sennheiser and Sony published, or is derived from it — what Sennheiser publishes and what Sony publishes, both counted.