The Moondrop Armature Art 24 is 5.8Ω at 96.6 dB/mW; the Moondrop HARMON is 19Ω 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.
In amplifier terms these two are the same headphone. The gap between what they need for 100 dB is under half a decibel, which is smaller than the step between two clicks of most volume controls.
| Specification | Armature Art 24 | HARMON |
|---|---|---|
| Impedance | 5.8 Ω | 19 Ω |
| Sensitivity | 96.6 dB/mW | 96.8 dB/mW |
| Sensitivity (voltage) | 119.0 dB/V | 114.0 dB/V |
| Power for 100 dB | 2.2 mW | 2.1 mW |
| Voltage for 100 dB | 0.11 V | 0.20 V |
| Current for 100 dB | 19.4 mA | 10.5 mA |
| Highest source impedance that leaves them alone (one-eighth rule) | 0.72 Ω | 2.38 Ω |
| Sources that reach 100 dB out of 280 | 279 | 280 |
1 of the 280 sources has the power for the HARMON but not for the Armature Art 24 — Steinberg UR22C.
49 sources are low enough in output impedance for the HARMON under the one-eighth rule but not for the Armature Art 24 (FiiO SnowSky Tiny B, FiiO KA13, FiiO KA15, 46 more).
279 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: Moondrop Armature Art 24 and Moondrop HARMON. Every figure on this page comes from what Moondrop published, or is derived from it — what that maker publishes, counted.