The Beyerdynamic DT 990 Pro (250Ω) is 250Ω at 96.0 dB (no reference unit printed); the Sennheiser HD 800S 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 Beyerdynamic DT 990 Pro (250Ω) needs 0.8 dB more than the Sennheiser HD 800S to reach the same loudness — 2.5 mW against 2.1 mW.
| Specification | Beyerdynamic DT 990 Pro (250Ω) | Sennheiser HD 800S |
|---|---|---|
| Impedance | 250 Ω | 300 Ω |
| Sensitivity | 96.0 dB | 96.8 dB/mW |
| Sensitivity (voltage) | 102.0 dB/V | 102.0 dB/V |
| Power for 100 dB | 2.5 mW | 2.1 mW |
| Voltage for 100 dB | 0.79 V | 0.79 V |
| Current for 100 dB | 3.2 mA | 2.6 mA |
| Highest source impedance that leaves them alone (one-eighth rule) | 31.25 Ω | 37.50 Ω |
| Sources that reach 100 dB out of 280 | 277 | 277 |
One caution before reading the rows. Beyerdynamic DT 990 Pro (250Ω) printed a decibel figure with no reference unit, so this page reads it as per milliwatt. If it is really per volt, that model needs far more than the table says. Why the two readings differ by so much.
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.
1 source is low enough in output impedance for the Sennheiser HD 800S under the one-eighth rule but not for the Beyerdynamic DT 990 Pro (250Ω) (Arturia AudioFuse Rev2).
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: Beyerdynamic DT 990 Pro (250Ω) and Sennheiser HD 800S. Each figure on this page is labelled on those pages with where it came from, including the ones Beyerdynamic and Sennheiser never published — what Beyerdynamic publishes and what Sennheiser publishes, both counted.