| Model name | IM4 |
|---|---|
| Connectivity technology | Wired |
| Included components | User Manual |
| Age range (description) | Adult |
| Material | Aluminum |
| Specific uses for product | Gaming, Music |
| Compatible devices | Cellphones, Music Production Equipment, Gaming Consoles, Desktops, Tablets, Laptops, Smart Speaker |
| Unit count | 1 Count |
| Control method | Touch |
| Number of Items | 10 |
| Manufacturer | FOSI AUDIO |
| Place of Business | Shenzhen Foresight Technology Co.Ltd,Dalang street,ShenZhen,Guangdong,518000,+86 17722625601 |
| Model | IM4-B |
| Part Number | IM4-B |
| Hardware interface | 3.5mm Audio |
| Special features | Open-Back Design, Dual Magnet & Dual Chamber, Beryllium Driver, Custom Tuning, Detachable Cable, Customizable Sound |
| Batteries included | No |
| Batteries Required | No |
| Material Type | Aluminum |
| Supports Bluetooth Technology | No |
| Manufacturer | FOSI AUDIO |
| Item model number | IM4-B |
| Parcel Dimensions | 17.5 x 12.8 x 5.7 cm; 300 g |
| ASIN | B0FXLF31Y6 |
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Additional Information
| Date First Available | Nov. 7 2025 |
|---|---|
| Customer Reviews |
4.1 out of 5 stars |
| Â鶹Çø Rank |
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From the brand
Amplifying Your Voice, Shaping Our Innovation
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Guided by our mission of "Redefining HiFi with Unmatched Value", Fosi Audio continues to fuel its passion for the Hifi industry, ramp up R&D efforts, and co-create new HiFi equipment with users. We pledge to bring more amazing Hifi gear with high value for the price, innovative design, cutting-edge technology, and premium quality, to audiophiles worldwide.
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DAC Amplifier for you!
Product Description
Open-Back In-Ear Monitor
Fosi Audio IM4
A new exploration designed for long-lasting comfort in sound and fit.
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High-Performance Dynamic Unit
Engineered with an optimized dynamic driver and acoustic tuning for detailed sound (THD<1% ).
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Rich Sound Details
A 10mm Be-PU driver for dense mid-Lows, brilliant highs, and a wide, detailed soundstage.
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Hi-performance Single Driver, Pure Excellence
No driver stacking, just pure sound.IM4's single dynamic driver delivers coherent and layered audio.
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Perfect Balance of Acoustic Space
Dual-chamber control: a 9-port front for balance, a sealed rear for treble extension.
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Ensure pure Signal Transmission
4-strand 392-core 5N OFC silver-plated cable: signal transmission stable gold-plated connectors.
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Pocket-sized, Expansive Soundscape.
Wide-open construction minimizes internal reflections,pressure buildup for an open, natural sound.
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Acoustic Damping for Pure Sound
The rear chamber is filled with sound-damping material to eliminate resonance peaks and harshness.
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Ergonomic Build for Comfort
Universal, comfortable fit, engineered from millions of ear scans for a secure and lightweight feel.
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Balanced Tuning Across Genres
Punchy bass, clear mids, and spacious, sibilance-free treble. IM4 is tuned for relaxed listening.
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Enjoy All-day Comfort
Each earbud weighs only 7g, ensuring pressure-free comfort for long listening.
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Two Bold Finishes
Black exudes understated elegance, while silver shines with refined brilliance.
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Explore More Sound Styles
Triple-tunable ear tips in three sizes adapt to ears, allowing you to customize the bass response.
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Aluminum Alloy Conduit and Brass Nozzle
Tailor your sound: an aluminum nozzle for warm bass or a brass one for clear mids and treble.
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2-Pin 0.78mm Connectors
Braided cable with a 3.5mm plug, easily upgrade to 3.5mm or 4.4mm cables for flexible customization.
Which Fosi Audio headphone or headphone amp is right for you?
 Fosi Audio i5 |  Q4 |  SK01 |  SK02 |  DS1 |  DS2 |  K5 Pro | |
|---|---|---|---|---|---|---|---|
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Customer Reviews
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37
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3,060
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396
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283
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431
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312
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1,336
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Type
| i5 Open-Back Headphones | DAC+Headphone Amp | Headphone Amplifier/Preamp | DAC+Headphone Amplifier/Preamp | DAC+Headphone Amp | DAC+Headphone Amp | DAC+Headphone Amp |
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MAX Power Output/Specification
| Open-ended | Active speakers or Amplifiers | 2400³¾°Â°ª32¦¸(±á¾±²µ³ó | 3.5mm: 280mW, 4.4mm: 1100mW | 120mW@32 Ohm(SE) | 120mW@32 Ohm(SE) | Active speakers or Amplifiers |
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Input
| x | PC-USB + Optical + Coaxial | 3.5mm line in | USB + Optical | Type C+ USB A | Type C+ USB A | USB-C + Optical + Coaxial |
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Output
| 1.5M&3.5mm3.5mmHeadphone | RCA + 3.5mm Headphone | 3.5mm/6.35mm headphone jack | Headphone Jack, 3.5mm AUX/OPT" | 3.5mm 4.4mm Headphone | 3.5mm 4.4mm Headphone | RCA + 3.5mm Headphone |
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Treble & Bass Control
| x | ? | ? | x | x | x | ? |
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Earphone diaphragm size
| 97MM | x | x | x | x | x | x |
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THD
| x | ¡Ü0.01% | <0.001% | ¡Ü0.001% | ¡Ü 0.0006%(SE) ¡Ü 0.001%(BAL) | <0.0001% | <0.003% |
|
SNR
| 98dB | ¡Ý105»åµþ | ¡Ý108»åµþ | ¡Ý120»åµþ | ¡Ý120»åµþ | ¡Ý130»åµþ | >110dB |
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Terminating Impedance
| x | 16-200 Ohm | 16-300 Ohm | 16-300 Ohm | 16-300 Ohm | 16-300 Ohm | 16-300 Ohm |
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PC-USB Input Sampling Rate
| x | 24bit/96kHz | - | 32bit/384kHz | 32bit/768kHz | 32bit/768kHz | 24bit/96kHz |
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Diaphragm thickness
| 2umPET | x | x | x | x | x | x |
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Earphone Case Material
| Leather + Canvas + Sponge | x | x | x | x | x | x |
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