Etymotic ER4XR
The Etymotic ER4XR is a single balanced-armature in-ear monitor housed in a CNC-machined anodized aluminum body with a detachable, user-replaceable cable using a customized MMCX connector. It is the bass-tuned variant of Etymotic's ER4 series, sharing the same driver type as the flat-tuned ER4SR but with added low-frequency output, and each pair ships with a channel-matching compliance certificate.
| Frequency response | 20 Hz – 16 kHz |
| Sensitivity | 98 dB @ 1kHz, 1mW |
| Impedance | 45 Ω |
As stated by the manufacturer — not community data.
A dongle is enough
A phone's own output runs out early; a small USB DAC/amp gives it full level and headroom.
| Needs, for 110 dB peaks | 0.84 V · 16 mW |
| Phone or laptop (≈0.70 V, 20 mW) | Runs short |
| Dongle DAC/amp (≈2.0 V, 120 mW) | Enough |
Worked out from the stated 98 dB/mW and 45 Ω — not a listening test. DAC/amps on the shelf →
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