Fosi Audio IM4 Open-Back In-Ear Monitor/Headphones

The IM4 Pre-Sale is Now Live

Fosi Audio IM4

Open-Back In-Ear Monitor

The IM4 Pre-Sale is Now Live

Fosi Audio IM4

Open-Back In-Ear Monitor

A New Exploration

The IM4 is our first step into the world of IEMs, crafted to reflect Fosi Audio’s signature style in both aesthetics and sound.

The name “IM4” resonates with the phrase “I am for” : a declaration of support, advocacy, and identity.

Refined with audiophile feedback, the IM4 delivers a balanced, relaxed and versatile listening experience.

And this is just the beginning, more earphones are coming soon.

Hear the Unheard

Reveal a World of New Detail

Dual-Magnet Dual-Cavity Driver

Thanks to the low-distortion (THD＜1%) driver system, the IM4 delivers great detail resolution and high impulse fidelity. Combined with expert tuning, it provides a balanced, fatigue-free sound for extended listening sessions.

PU Beryllium-Plated Diaphragm

The 10mm diaphragm is not only light and thin but also highly rigid, delivering dynamic bass and sparkling treble. It ensures outstanding clarity and detail across the entire sound spectrum.

Single Driver, Pure Excellence

IM4 features a high-quality single dynamic driver only but performs just as well as multi-driver setup. Its balanced tuning allows vocals and instruments to flow together naturally, delivering a smooth, layered sound that stays true to the music.

High-Strength N52 Dual Magnets

This design provides a powerful, stable magnetic field that enables accurate, lightning-fast dynamic response and effectively reduces nonlinear distortion to produce purer, more natural sound.

Dual-Chamber Construction

To achieve a natural sound, our engineers employed dual chambers to precisely control airflow and pressure. The front chamber’s nine-port design ensures balanced frequencies, while the rear chamber extends treble detail.

Dual-Magnet Dual-Cavity Driver

PU Beryllium-Plated Diaphragm

The 10mm diaphragm is not only light and thin but also highly rigid, delivering dynamic bass and sparkling treble. It ensures outstanding clarity and detail across the entire sound spectrum.

High-Strength N52 Dual Magnets

This design provides a powerful, stable magnetic field that enables accurate, lightning-fast dynamic response and effectively reduces nonlinear distortion to produce purer, more natural sound.

Single Driver, Pure Excellence

Dual-Chamber Construction

5N OFC Silver-Plated Cable

Braided with 4 strands of 392-core 5N high-purity OFC silver-plated wire, the cable offers excellent signal transmission and shielding. And the gold-plated connector provides a more stable connection.

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Open-Back Build for Spacious Soundstage

The wide-open construction minimizes internal reflections and pressure buildup, delivering a more open, natural sound with reduced fatigue. It offers you a personal concert hall on demand and an immersive listening experience.

Meticulously Tuned for Enjoyable Listening

Crafted with audiophile feedback, IM4 is fine-tuned over many iterations. It brings you a neutral, smooth, and non-fatiguing sound that makes your music feel closer—more alive and vivid.

Acoustic Damping for Pure Sound

The rear chamber is filled with sound-damping material to eliminate resonance peaks and harshness, which might distort the sound signature and reduce listening pleasure.

Balanced Tuning across Genres

IM4 delivers punchy bass and clearer treble without smearing the midrange, making it ideal for relaxed, extended sessions. A subtle treble lift adds spaciousness and precise imaging, all without a hint of sibilance.

Deep Bass Ear Tips

Bass Ear Tips

Balanced Ear Tips

No Ear Tips

Ergonomic Build for Comfort

Developed with insights from millions of ear shape samples, the ergonomic housing adapts to diverse ear contours, offering a secure, lightweight, and seamless fit.

Only 7g per Earbud

The hollowed structure cuts weight to just 38g with the cable, ensuring pressure-free comfort for long listening.

All-Aluminum Alloy CNC Construction

Crafted from CNC-machined 6063 aluminum alloy with a sandblasted and anodized finish, the housing is durable and offers a smooth touch that’s gentle on the skin.

Elegant Colors

Two color options: black exudes understated elegance, while silver shines with refined brilliance.

Swappable Components

Triple-tunable ear tips in three sizes adapt to your ear shape, letting you pick the bass response you like best.

To maximize flexibility, the package comes with two sound nozzles: aluminum for reduced sibilance and added bass, brass for clearer mids and treble.

Braided cable with 2-Pin 0.78mm connectors and a 3.5mm plug, easily upgrade to 3.5mm or 4.4mm cables for flexible customization.

Specifications

General Specs

Shell Material

Driver Unit

Diaphragm

Sensitivity

Impedance

Frequency Response

Cable

Connector

Audio Jack

Weight (per earbud)

Weight (incl. cable)

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Fosi Audio IM4

Fosi Audio IM4

Open-Back In-Ear Monitor

A New Exploration

Hear the Unheard

Dual-Magnet Dual-Cavity Driver

PU Beryllium-Plated Diaphragm

Single Driver, Pure Excellence

High-Strength N52 Dual Magnets

Dual-Chamber Construction

Dual-Magnet Dual-Cavity Driver

PU Beryllium-Plated Diaphragm

High-Strength N52 Dual Magnets

Single Driver, Pure Excellence

Dual-Chamber Construction

5N OFC Silver-Plated Cable

Open-Back Build for Spacious Soundstage

Meticulously Tuned for Enjoyable Listening

Acoustic Damping for Pure Sound

Balanced Tuning across Genres

Ergonomic Build for Comfort

Only 7g per Earbud

All-Aluminum Alloy CNC Construction

Elegant Colors

Swappable Components

Specifications

Package Contents

You've unlocked an exclusive 20% early-bird discount on the IM4.

CODE: IM4EB20