Experience a more spacious and engaging listening experience with the Fosi Audio IM4, an open-back IEM designed for listeners who want detailed sound, strong instrument separation, and a natural sense of space in a compact in-ear design.

Fosi IM4 is a 10mm N52 dual-magnet, dual-cavity dynamic driver with a PU beryllium-coated diaphragm. Combined with its open-back acoustic design, the IM4 delivers an airy presentation with clear separation and lively dynamics. Independent listening tests highlight its spacious soundstage, fast bass response, clean detail retrieval, and strong overall coherence.

The IM4 also gives you control over its sound. Two interchangeable nozzles, aluminum and brass, allow you to adjust the character of the presentation, while three types of ear tips are included in multiple sizes: Balanced, Bass, and Deep Bass. This makes it easier to fine-tune both the sound and fit to suit your preferences.

Built from precision-machined 6063 CNC aluminum alloy, each earpiece weighs approximately 7g. The lightweight construction and open-back design help provide a comfortable fit for extended listening sessions.

A detachable 0.78mm 2-pin cable is included, featuring 392-strand 5N OFC silver-plated copper construction and a gold-plated 3.5mm plug. The cable can be replaced or upgraded as your setup evolves.

Key Features:

• Open-back in-ear monitor design for an airy, spacious presentation
• 10mm N52 dual-magnet, dual-cavity dynamic driver
• PU beryllium-coated diaphragm
• Interchangeable aluminum and brass tuning nozzles
• Three ear-tip profiles: Balanced, Bass, and Deep Bass
• 6063 CNC aluminum alloy shells
• Detachable 0.78mm 2-pin cable
• 109dB sensitivity and 21Ω impedance
• 20Hz–20kHz frequency response
• Approximately 7g per earpiece
• 3.5mm gold-plated audio connector

What’s Included:

• Fosi Audio IM4 IEMs
• 3.5mm detachable cable
• Balanced ear tips
• Bass ear tips
• Deep Bass ear tips
• Aluminum nozzle
• Brass nozzle
• Carrying pouch
• User manual and quick guide