The Sennheiser EW IEM G4 TWIN A1 System In Ear Monitor is a professional wireless in-ear monitoring system operating in the A1 band (470–516 MHz), and part of the renowned Evolution Wireless G4 series. Includes a half-rack SR IEM G4 stereo transmitter, constructed entirely of metal with a high-contrast OLED display for complete control, and two EK IEM G4 bodypack receivers, as well as two IE 4 earphones.

It offers up to 1680 selectable frequencies spread over a bandwidth of up to 42 MHz, supporting up to 16 compatible channels, with rapid infrared synchronisation between transmitter and receivers. The audio transmission uses Wideband FM stereo modulation (MPX pilot tone) with HDX compander, a signal-to-noise ratio greater than 90 dB and total harmonic distortion less than 0.9%. The transmitter has balanced audio inputs (2 x XLR/jack combo), balanced audio output, 50 Ω BNC antennas, RF power switchable between 10, 30 and 50 mW depending on regulations, and coverage up to approximately 100 metres.

In summary, the EW IEM G4 TWIN A1 combines robustness, frequency flexibility, high audio quality and quick setup, ideal for live and stage use.