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The Fosi Audio IM4 is a revolutionary In-Ear Monitor (IEM) that brings the natural, airy acoustics of open-back headphones into a portable in-ear design. Engineered for critical listening and audio enthusiasts, the IM4 delivers an exceptionally wide soundstage and precise imaging.
Innovative Open-Back Architecture: Unlike typical sealed IEMs, the IM4 features a unique open-back structure. This design significantly reduces pressure build-up and delivers a more open, spacious, and natural sound presentation, minimizing the "in-your-head" feeling common with traditional monitors.
High-Fidelity Dynamic Driver: The IM4 utilizes a large, high-performance dynamic driver capable of delivering deep, controlled bass, a rich and textured midrange, and crisp, extended high frequencies. The sound signature is balanced and transparent, designed for accurate audio reproduction.
Ergonomic and Comfortable Fit: Built with lightweight materials and an ergonomic housing shape, the IM4 ensures long-term comfort for extended listening sessions. The secure fit provides good passive noise isolation while maintaining the intended open sound quality.
Detachable Cable for Upgradeability: The IEMs feature a standard, reliable connector (e.g., 2-pin or MMCX, depending on the model specification) that allows users to easily replace the cable or upgrade to a balanced cable for use with high-quality DACs and amplifiers, maximizing performance.
Premium Build Quality: Constructed with durable materials, the Fosi Audio IM4 is designed to withstand daily use. The included cable is designed for low microphonics, ensuring a clean signal path and minimal interference during movement.
The Fosi Audio IM4 is the ideal choice for audiophiles seeking an IEM that combines the intimacy of an in-ear monitor with the expansive soundstage and natural acoustics of a high-end open-back headphone.
Open-Back In-Ear Monitor
A new exploration designed for long-lasting comfort in sound and fit.
Engineered with an optimized dynamic driver and acoustic tuning for detailed sound(THD<1%)
Dual-Magnet Dual-Cavity
A 10mm Be-PU driver for dense mid-Lows, brilliant highs, and a wide
detailed soundstage.
Be-PU Diaphragm
No driver stacking, just pure sound. lM4's single dynamic driver delivers
coherent,layered, and authentically tuned audio.
Single Dynamic Driver
Dual-chamber control: a 9-port front for balance, a sealed rear for treble
extension.
Dual-Chamber Design
4-strand 392-core 5N 0FC silver-plated cable: excellent signal transmission
and a stable gold-plated connection.
5N OFC Cable
Wide-open construction minimizes internal reflections and
pressure buildup for an open, natural sound.
Open-Back Design
The rear chamber is filled with sound-damping material to eliminate
resonance peaks and harshness.
Acoustic Damping
A Universal, comfortable fit, engineered from millions of ear scans for a
secure and lightweight feel.
Ergonomic Design
Punchy bass, clear mids, and a spacious, sibilance-free treble. The lM4 is
tuned for relaxed listening.
Balanced Tuning
Each earbud weighs only 7g,ensuring pressure-free comfort for long
listening.
Hollow Structure Design
Black exudes understated elegance, while silver shines with refined
brilliance.
Elegant Colors
Triple-tunable ear tips in three sizes adapt to your ears, allowing you to
customize the bass response.
Swappable Ear Tips
Tailor your sound: an aluminum nozzle for warm bass or a brass one for
clear mids and treble.
Tuning Nozzles
Braided cable with a 3.5mm plug, easily upgrade to 3.5mm or 4.4mm
cables for flexible customization.
Detachable Cable
Shell Material:6063 CNC Aluminum Alloy
Driver Unit:10 mm N52 Dual-Magnet Dual-Cavity Dynamic Driver
Diaphragm:PU Beryllium-coated Diaphragm
Sensitivity:109dB
Impedance:21Ω
Frequency Response:20Hz–20kHz
Cable:4-core 392-strand 5N OFC Silver-plated Copper Cable
Connector:2-PIN 0.78mm
Audio Jack:3.5 mm Gold-plated Plug
Weight (per earbud):7g ±0.5g
Weight (incl. cable):38g ±1g
Unlike traditional closed-back earbuds that trap air and sound pressure, the Fosi Audio IM4 Open-Back design allows for natural air exchange. This results in a wider, more expansive soundstage and a sense of "airiness" typically only found in full-sized open-back studio headphones. It significantly reduces the "in-head" feeling, providing a more lifelike and fatigue-free listening experience during long sessions.
Yes, comfort is a key advantage of the IM4. The open-back architecture helps relieve air pressure on the eardrums, which is a common cause of listener fatigue with standard IEMs. Additionally, the ventilation allows for better heat dissipation, keeping your ears cooler. This makes the IM4 an excellent choice for audiophiles and gamers who wear monitors for several hours at a time.
Because the IM4 is an open-back monitor, there is a natural amount of "sound leakage" by design. This transparency is what allows for the superior soundstage and natural tonality. While it is perfect for critical listening in quiet home or studio environments, it is not recommended for use in very loud public spaces or libraries where absolute isolation is required.
The Fosi Audio IM4 is tuned for transparency and tonal balance. The open-back design ensures that the bass is fast and well-defined without being "boomy," while the mids and highs are allowed to breathe with exceptional clarity. This makes the IM4 particularly well-suited for acoustic music, jazz, classical, and any genre where instrument separation and imaging are crucial.
Yes, the IM4 features a detachable cable design (typically using standard 2-pin or MMCX connectors). This is a vital feature for high-end IEMs, as it allows users to easily upgrade to premium balanced cables or replace the cable if it gets damaged. It ensures the longevity of your investment and allows for further customization of your audio signal path.
