ER4XR
headphones
$310
Used market: $240*
Specifications
3 of 6 values have a recorded sourceExpert Audio Engineering Commentary
Tonal Profile
45 Ω and 98 dB/mW — about 112 dB/V, the least efficient load in this batch and the highest impedance. Etymotic ships a channel-matching compliance certificate with it, which is a fair summary of what the money buys.
Amplification Warning
The one in-ear here that behaves like a small pair of headphones: a weak phone output will clip before it gets loud on dynamic material. It is also the one that will not hiss on a mediocre source.
What the datasheet actually says
Quoted verbatim from the manufacturer’s own page, with the date we checked it. We state what is printed, not what anyone intended by it.
«Impedance: 45 Ohms @ 1kHz / Sensitivity: 98 dB @ 1kHz, 1mW»
The ER4SR page carries the identical pair of figures — 45 Ohms and 98 dB @ 1 kHz, 1 mW. ER4SR is the studio-reference tuning and ER4XR the extended-bass one; Etymotic states the difference is in the acoustic response, not the electrical load. That may well be true, but it means these two numbers cannot tell you which model you are looking at, and the same pattern repeats one tier down with the ER2SE and ER2XR.
checked 8/5/2026* Estimated with the depreciation fallback (~77% retained value). · checked on 8/5/2026