The Shure SE215 is 17Ω at 107.0 dB/mW; the Shure SE846 is 9Ω at 114.0 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 SE215 needs 7.0 dB more than the SE846 to reach the same loudness — 0.20 mW against 0.04 mW.
| Specification | SE215 | SE846 |
|---|---|---|
| Impedance | 17 Ω | 9 Ω |
| Sensitivity | 107.0 dB/mW | 114.0 dB/mW |
| Sensitivity (voltage) | 124.7 dB/V | 134.5 dB/V |
| Power for 100 dB | 0.20 mW | 0.04 mW |
| Voltage for 100 dB | 58 mV | 19 mV |
| Current for 100 dB | 3.4 mA | 2.1 mA |
| Highest source impedance that leaves them alone (one-eighth rule) | 2.12 Ω | 1.12 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.
11 sources are low enough in output impedance for the SE215 under the one-eighth rule but not for the SE846 (FiiO KA13, FiiO K11, Schiit Vali 2+, 8 more).
33 sources stay below the audible-hiss threshold with the SE215 but cross it with the SE846 (Kiwi Ears Allegro Mini, FiiO KA13, JDS Labs Atom+ (2nd gen), 30 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 SE215 and Shure SE846. Every figure on this page comes from what Shure published, or is derived from it — what that maker publishes, counted.