STAX SR-003MK2 – electrostatic performance in an in-ear design

The STAX SR-003MK2 is a specialised electrostatic in-ear earspeaker created for listeners who want a compact alternative to a full-size STAX model. Its redesigned ear-canal structure sits at the ear without covering the entire outer ear, making it suitable for focused listening at a desk, in a dedicated personal audio system or wherever a lighter wearing format is preferred. This is not a conventional earphone intended for a phone, laptop headphone socket or standard headphone amplifier. It uses a five-pin STAX PRO bias connector and must be partnered with a compatible STAX driver unit or adapter fitted with a corresponding five-pin PRO bias output.

A circular push-pull electrostatic sound element forms the technical foundation of the SR-003MK2. Its diaphragm is approximately 15% lighter than the diaphragm used in the S-001/MK2, reducing moving mass in support of fast transient response, fine resolution and a transparent presentation. The specified frequency response is 20 Hz to 20 kHz with a 4 dB tolerance, while capacitance is rated at 44 pF including the attached cable. Sensitivity is specified as 110 dB at 100 V rms and 1 kHz, and the required DC bias voltage is between 550 and 580 V. Three silicone earbud sizes are supplied—small, medium and large—with the medium size fitted as standard.

The fixed 1.5-metre parallel six-core cable is designed for direct connection to a suitable STAX PRO bias system and provides practical reach for most desktop or nearby equipment arrangements. Testing all three silicone sizes is recommended, as a secure and comfortable fit helps maintain stable positioning and consistent sound from one listening session to the next. Remove and clean the silicone pieces carefully when required, allow them to dry completely and keep moisture away from the electrostatic housings. The connector should always be handled by its plug rather than pulled by the cable. For listeners building a compact electrostatic headphone system, the STAX SR-003MK2 offers a distinctive way to experience detailed listening without using a conventional over-ear design.