The Shure SE315 is 27Ω at 116.0 dB/mW; the Shure SE535 is 36Ω at 119.0 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 SE315 needs 3.0 dB more than the SE535 to reach the same loudness — 0.03 mW against 0.01 mW.
| Specification | SE315 | SE535 |
|---|---|---|
| Impedance | 27 Ω | 36 Ω |
| Sensitivity | 116.0 dB/mW | 119.0 dB/mW |
| Sensitivity (voltage) | 131.7 dB/V | 133.4 dB/V |
| Power for 100 dB | 0.03 mW | 0.01 mW |
| Voltage for 100 dB | 26 mV | 21 mV |
| Current for 100 dB | 1.0 mA | 0.6 mA |
| Highest source impedance that leaves them alone (one-eighth rule) | 3.38 Ω | 4.50 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.
4 sources stay below the audible-hiss threshold with the SE315 but cross it with the SE535 (FiiO KA13, Fosi Audio K7, Chord Hugo 2, 1 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 SE315 and Shure SE535. Every figure on this page comes from what Shure published, or is derived from it — what that maker publishes, counted.