Explorers in Sound: Why We Created the i5
At Fosi Audio, we’ve always been driven by a passion to explore the frontiers of sound. We listen closely to our users, and over the years, a growing voice among audiophiles became impossible to ignore: “Make high-end planar magnetic headphones more accessible.”
After over two years of development and countless iterations, that vision became reality. The i5 is the answer—our first planar magnetic headphone, built not just for performance, but for those who truly live for music.
Developed in collaboration with leading diaphragm material manufacturers, the i5 brings advanced planar magnetic technology to a broader audience. It reflects our belief that exceptional sound should no longer be a luxury reserved for the few—it should be an experience shared by many.
What Makes the i5 a Breakthrough in Sound?
The i5 isn’t just another headphone—it’s a technological leap. With a fully reimagined driver system, groundbreaking materials, and a user-first design, the i5 delivers:
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Unmatched clarity across the frequency spectrum
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Industry-leading group delay and dynamic range
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A soundstage and resolution comparable to electrostatics—at a fraction of the cost
Let’s break down what makes this possible.
Inspired by Philosophy: The Voice Coil Redefined
In designing the i5’s voice coil, we drew from Eastern philosophy—specifically, the principle that "Heaven is round, Earth is square."
This inspired a hybrid design:
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A round diaphragm that promotes even force distribution
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A square printed circuit that optimizes signal transmission
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A 44-piece neodymium magnet array for enhanced magnetic strength and field uniformity
Together, this system achieves powerful, distortion-free sound with greater driving force and accuracy.
Advanced Coil Coating for Superior Performance
To push boundaries further, we applied magnetron sputtering technology to build a three-layer composite voice coil:
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Nickel-cobalt alloy (outer layers)
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Pure silver (inner layer for high conductivity)
At just 1.3μm thick, this ultra-thin structure ensures:
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High conductivity with minimal resistance
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Mechanical reliability over time
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Improved transient response for sharper, faster sound
Diaphragm Innovation: 2μm PET, 97mm Wide
At the heart of the i5 lies an ultra-thin, high-strength 2μm PET diaphragm with a 97mm diameter—one of the largest in its class.
What this delivers:
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Faster transient response
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More detailed, dynamic playback
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A larger, more spacious soundstage
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Greater instrument separation and realism
Every instrument is placed with precision. Every note has room to breathe.
Open-Back Design: Natural, Wide, and Clean
Many closed-back designs suffer from internal reflections and pressure buildup that cloud the sound. The i5’s fully open-back rear cavity solves this, offering:
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Clean, airy sound with low distortion
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A soundstage that feels immersive and three-dimensional
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No pressure buildup, eliminating listening fatigue over long sessions
It’s the openness of electrostatic headphones—without their bulk or price.
Wearable Comfort, Engineered with Purpose
Long listening sessions demand more than good sound—they demand comfort. That’s why we focused as much on ergonomics as on acoustics.
Comfort Features Include:
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Earcups made of breathable, perforated leather composite:
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Skin-friendly
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Soft to the touch
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Ventilated for extended use
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Headband system with:
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A memory-alloy core that flexes to your head
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A genuine leather strap for premium feel
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Silicone sliding buckles for precise, secure adjustment
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The result: a custom fit for every head shape, without pressure points or discomfort.
What Kind of Music Experience Does the i5 Deliver?
With the i5, we didn’t just aim to create a headphone. We set out to deliver an emotional, immersive music experience that rivals far more expensive gear.
You’ll hear:
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The shimmer of cymbals with lifelike clarity
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The warmth of analog vocals without coloration
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The space between instruments, just as they were recorded
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The soul of the performance, not just the sound
Whether it’s jazz, classical, indie, or electronic, the i5 reveals nuance, texture, and detail in ways you’ve never experienced before—turning music into memory.
The i5 is More Than a Headphone
The i5 marks a new chapter for Fosi Audio—a journey into the planar magnetic world where performance meets artistry, and accessibility meets innovation.
We built the i5 because we believe high-end sound should belong to more people. It’s a headphone that doesn't just play music—it unlocks it.
Welcome to the i5 experience. Hear everything. Feel everything.