The Etymotic ER4XR is 45Ω at 98.0 dB/mW; the Shure SE215 is 17Ω at 107.0 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 Etymotic ER4XR needs 9.0 dB more than the Shure SE215 to reach the same loudness — 1.6 mW against 0.20 mW.
| Specification | Etymotic ER4XR | Shure SE215 |
|---|---|---|
| Impedance | 45 Ω | 17 Ω |
| Sensitivity | 98.0 dB/mW | 107.0 dB/mW |
| Sensitivity (voltage) | 111.5 dB/V | 124.7 dB/V |
| Power for 100 dB | 1.6 mW | 0.20 mW |
| Voltage for 100 dB | 0.27 V | 58 mV |
| Current for 100 dB | 5.9 mA | 3.4 mA |
| Highest source impedance that leaves them alone (one-eighth rule) | 5.62 Ω | 2.12 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.
1 source is low enough in output impedance for the Etymotic ER4XR under the one-eighth rule but not for the Shure SE215 (Shanling H5).
8 sources stay below the audible-hiss threshold with the Etymotic ER4XR but cross it with the Shure SE215 (FiiO BTR11, FiiO K11 R2R, Lake People G103-S Mk II, 5 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: Etymotic ER4XR and Shure SE215. Every figure on this page comes from what Etymotic and Shure published, or is derived from it — what Etymotic publishes and what Shure publishes, both counted.