Electrostatic Universal IEM (Sonion EST Quad)
Specifications
| Category | Iem |
|---|---|
| Brand | Reference Audio |
| Driver type | Electrostatic |
| Driver size | n/a mm |
| Driver count | 4 EST per side |
| Impedance | n/a (EST) Ω |
| Sensitivity | n/a (EST) |
| Frequency response | 20 Hz – 70 kHz |
| THD | 0.05 % |
| Cable termination | detachable |
| Recommended amp power | n/a mW |
| Tuning target | ultra-fast transients, treble-extended |
| Weight | 8.1 g |
| Price (USD) | $4299 |
| Release year | 2025 |
Overview
Pure electrostatic universal IEM built around four Sonion EST tweeters — the only universal IEM in the database without any moving-coil driver. The film diaphragm is bias-charged with a high-voltage rail provided by the source-side EST adapter and modulated by the audio signal across the stator plates.
Trade-off: the fastest transients available in any audio transducer (the diaphragm mass is near-zero), but a complex source requirement. Compatible only with sources that include the EST bias module — typically high-end DAPs and dedicated EST-capable desktop amps.
Niche; expensive; technically impressive. For the more practical implementation of the topology see the tribrid IEM which uses ESTs only for super-tweeter duty above 8 kHz.
Earpiece / cable connector
Pentaconn Ear — Premium IEM Connector
2.5mm · 2-pole 2-pin