Fosi Audio IM4 10mm Dual-Cavity Dynamic Driver Open-Back In-Ear Monitor Earphone

Fosi Audio IM4 Open-Back In-Ear Monitor with Dual-Cavity Design

Revolutionary open-back design meets dual-cavity acoustic engineering—experience natural, spacious sound with exceptional comfort.

The Fosi Audio IM4 represents a breakthrough in open-back IEM design, featuring an innovative 10mm dual-cavity dynamic driver that delivers the expansive soundstage and natural tonality of open-back headphones in a compact, portable form factor. Unlike traditional closed IEMs, the IM4's open-back architecture eliminates acoustic pressure buildup, providing a more natural listening experience with reduced fatigue during extended sessions. With premium OFC silver-plated cable, ergonomic metal construction, and Fosi Audio's meticulous tuning expertise, the IM4 offers audiophile-grade performance for those who appreciate the unique characteristics of open-back sound.

Key Features

• Revolutionary Open-Back Design: Unlike conventional closed IEMs, the IM4's open-back architecture allows air to flow freely, creating a more natural, speaker-like soundstage with exceptional width and depth. Experience music the way it was meant to be heard—open, airy, and fatigue-free.
• Dual-Cavity Acoustic Structure: Innovative dual-cavity design separates and optimizes bass and mid-high frequency reproduction. The front cavity handles mids and highs with precision, while the rear cavity delivers controlled, textured bass without muddiness.
• 10mm High-Performance Dynamic Driver: Precision-engineered driver delivers exceptional detail retrieval, natural timbre, and accurate frequency response across the entire audio spectrum. The large diaphragm ensures powerful bass extension and smooth treble.
• Premium OFC Silver-Plated Cable: High-purity oxygen-free copper cable with silver plating provides excellent conductivity and minimal signal loss. The 3.5mm connector ensures universal compatibility with smartphones, DAPs, and desktop amplifiers.
• Ergonomic Metal Construction: Durable metal housing provides excellent acoustic damping and resonance control while maintaining a lightweight, comfortable fit for extended listening sessions.
• Natural Sound Signature: Fosi Audio's reference tuning emphasizes natural tonality, excellent instrument separation, and a spacious soundstage—perfect for critical listening and enjoying all music genres authentically.
• Comfortable Fit: Lightweight design and ergonomic nozzle angle ensure secure, fatigue-free wearing comfort for hours of listening pleasure.
• Versatile Application: Perfect for home listening, studio monitoring, and enjoying music in quiet environments where the open-back design's advantages shine.

Technical Specifications

What's in the Box

• Fosi Audio IM4 Open-Back In-Ear Monitors (1 Pair)
• Silicone Ear Tips - Small, Medium, Large (3 Pairs)
• Premium Carrying Case (1 Piece)
• User Manual (1 Copy)

Sound Signature & Performance

The Fosi Audio IM4 delivers a natural, reference-grade sound signature that showcases the advantages of open-back design:

• Bass: The dual-cavity structure provides deep, textured bass with excellent control and speed. Low-frequency extension is impressive, reaching down to 20Hz with authority. Bass is punchy and well-defined without the bloat or muddiness common in closed designs—perfect for all music genres.
• Midrange: Transparent, natural mids with exceptional detail retrieval. Vocals are rendered with lifelike presence and texture, while instruments maintain their authentic timbre. The open-back design contributes to an airy, uncongested presentation that reveals every nuance.
• Treble: Extended high-frequency response to 40kHz captures all the air and sparkle in your music. Treble is detailed and refined without harshness or sibilance, revealing micro-details and subtle textures that bring recordings to life.
• Soundstage: The open-back architecture creates an exceptionally wide and deep soundstage that rivals over-ear headphones. Imaging is precise with excellent instrument separation and layering, making these IEMs ideal for orchestral music, live recordings, and complex mixes.
• Dynamics: The 10mm driver handles dynamic contrasts beautifully—from whisper-quiet passages to explosive crescendos. The IM4 reproduces music with natural dynamics and effortless presentation.

Why Choose Open-Back IEMs?

Open-back in-ear monitors offer unique advantages that audiophiles appreciate:

• Natural Soundstage: The open design creates a more natural, speaker-like presentation with exceptional width and depth—far more spacious than closed IEMs.
• Reduced Listening Fatigue: No acoustic pressure buildup means you can listen for hours without the fatigue common with closed designs.
• Natural Tonality: Less acoustic interference from sealed chambers results in more accurate, natural sound reproduction.
• Airy Presentation: Music breathes naturally with an open, uncongested quality that's perfect for critical listening.
• Comfort: Reduced pressure on the ear canal provides superior comfort during extended listening sessions.

Dual-Cavity Acoustic Technology

The IM4's innovative dual-cavity structure provides significant acoustic advantages:

• Optimized Frequency Separation: Front and rear cavities are independently tuned to handle different frequency ranges, ensuring optimal performance across the spectrum.
• Enhanced Bass Control: The rear cavity provides dedicated bass tuning, delivering deep extension with excellent control and minimal distortion.
• Improved Clarity: Separating bass from mids and highs eliminates interference and masking, resulting in exceptional clarity and detail retrieval.
• Natural Resonance: Each cavity is precisely dimensioned to minimize unwanted resonances and standing waves.