The Audeze LCD-5 is 14Ω at 90.0 dB/mW; the Sennheiser HD 800 is 300Ω at 96.8 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 Audeze LCD-5 needs 6.8 dB more than the Sennheiser HD 800 to reach the same loudness — 10 mW against 2.1 mW.
| Specification | Audeze LCD-5 | Sennheiser HD 800 |
|---|---|---|
| Impedance | 14 Ω | 300 Ω |
| Sensitivity | 90.0 dB/mW | 96.8 dB/mW |
| Sensitivity (voltage) | 108.5 dB/V | 102.0 dB/V |
| Power for 100 dB | 10 mW | 2.1 mW |
| Voltage for 100 dB | 0.37 V | 0.79 V |
| Current for 100 dB | 26.7 mA | 2.6 mA |
| Highest source impedance that leaves them alone (one-eighth rule) | 1.75 Ω | 37.50 Ω |
| Sources that reach 100 dB out of 280 | 274 | 277 |
1 of the 280 sources has the power for the Audeze LCD-5 but not for the Sennheiser HD 800 — Sony NW-A306.
4 of the 280 sources have the power for the Sennheiser HD 800 but not for the Audeze LCD-5 — Zoom AMS-22, Tascam US-2x2HR, Roland Rubix22, 1 more.
24 sources are low enough in output impedance for the Sennheiser HD 800 under the one-eighth rule but not for the Audeze LCD-5 (Zoom AMS-22, Arturia MiniFuse 2, Arturia MiniFuse 1, 21 more).
273 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: Audeze LCD-5 and Sennheiser HD 800. Every figure on this page comes from what Audeze and Sennheiser published, or is derived from it — what Audeze publishes and what Sennheiser publishes, both counted.