The Shure AONIC 3 is 26Ω at 108.0 dB/mW; the Shure SE425 is 22Ω at 109.0 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 AONIC 3 needs 1.0 dB more than the SE425 to reach the same loudness — 0.16 mW against 0.13 mW.
| Specification | AONIC 3 | SE425 |
|---|---|---|
| Impedance | 26 Ω | 22 Ω |
| Sensitivity | 108.0 dB/mW | 109.0 dB/mW |
| Sensitivity (voltage) | 123.9 dB/V | 125.6 dB/V |
| Power for 100 dB | 0.16 mW | 0.13 mW |
| Voltage for 100 dB | 64 mV | 53 mV |
| Current for 100 dB | 2.5 mA | 2.4 mA |
| Highest source impedance that leaves them alone (one-eighth rule) | 3.25 Ω | 2.75 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.
9 sources stay below the audible-hiss threshold with the AONIC 3 but cross it with the SE425 (Lake People G103-S Mk II, FiiO M33 R2R, RME Babyface Pro FS, 6 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: Shure AONIC 3 and Shure SE425. Every figure on this page comes from what Shure published, or is derived from it — what that maker publishes, counted.