The ZMF Aeolus is 300Ω at 97.0 dB/mW; the ZMF Atrium Closed is 300Ω at 96.0 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 Atrium Closed needs 1.0 dB more than the Aeolus to reach the same loudness — 2.5 mW against 2.0 mW.
| Specification | Aeolus | Atrium Closed |
|---|---|---|
| Impedance | 300 Ω | 300 Ω |
| Sensitivity | 97.0 dB/mW | 96.0 dB/mW |
| Sensitivity (voltage) | 102.2 dB/V | 101.2 dB/V |
| Power for 100 dB | 2.0 mW | 2.5 mW |
| Voltage for 100 dB | 0.77 V | 0.87 V |
| Current for 100 dB | 2.6 mA | 2.9 mA |
| Highest source impedance that leaves them alone (one-eighth rule) | 37.50 Ω | 37.50 Ω |
| Sources that reach 100 dB out of 280 | 279 | 277 |
2 of the 280 sources have the power for the Aeolus but not for the Atrium Closed — Apple USB-C dongle (EU), Steinberg UR22C.
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: ZMF Aeolus and ZMF Atrium Closed. Every figure on this page comes from what ZMF published, or is derived from it — what that maker publishes, counted.