[Listening test] Fosi Audio i5 planar magnetic headphones

Product: Fosi Audio i5 - magnetostatic open-back headphones
Manufacturer: Fosi Audio - China
Approximate price: $/€600
Reviewer: Lucio Cadeddu - TNT-Audio Italy
Reviewed: December, 2025

Foreword

Fosi Audio is well known among enthusiasts for its compact, affordable Hi-Fi components. A few months ago, however the company ventured into new and unfamiliar territory - both in terms of product category and price range. The i5 headphones reviewed here represent an ambitious and sophisticated project, quite different from their usual offerings. These planar-magnetic headphones feature several unique characteristics (described below) and come in at just under €600, a price point far above what we typically associate with Fosi Audio. Since magneto-static (planar-magnetic) headphones are generally much more expensive, Fosi's challenge was to deliver high-end performance at a more accessible price for a wider audience.

A closer look

The technology used is sophisticated; you can find all the details directly on the official page. In a nutshell, these are the technical specifications:

Despite being fairly large and heavy headphones (over 500 grams), they are extremely comfortable to wear, thanks in part to a headband with a sort of memory function that naturally adjusts to the listener's head. The ear-cups are very soft and made from exceptionally comfortable materials, and the open-back design helps keep listening sessions from feeling oppressive while providing a more natural sound.

For this review, I tested several types of headphones and amplifiers, including extended comparison sessions with the acclaimed Audeze LCD-2 (2020 model), which use the same technology and retail for just under €1,000.

Is Fosi upping the ante?

Not all the Fosi products we've reviewed have managed to impress us, so some caution had to be taken when approaching a flagship product like this. Had they really done their homework before venturing into such unfamiliar territory? The answer is yes! These Fosi i5s are exceptionally convincing, natural-sounding headphones that immediately reminded me of some of the hallmark traits of loudspeakers using the same technology. Hyper-detail gives way to transparency and naturalness; nothing feels aggressive or overdone. Music flows effortlessly and pleasantly, making the i5 perfect for very long listening sessions. The sound is never fatiguing, yet remains consistently transparent and precise.

The bass frequencies can extend very, very deep, though they lack some of the punch typical of dynamic headphones in a similar price range. It's a planar kind of bass: clean, extended, and articulate, but never truly rude. To put it bluntly, it doesn't deliver the extreme impact of the IEMs reviewed a few weeks ago, the Yanyin Canon Pro, which strike the listener with greater force and raw energy. Nor is it quite the same as the bass of the Audeze LCD-2, which is more energetic but at times somewhat bloated and less controlled. The i5's bass strengths lie in its articulation, linearity, and depth.

In the midrange, vocals and acoustic instruments take on a fluid quality, never becoming monitor-like. These are certainly not the hyper-analytical headphones a sound engineer might choose when needing to dissect every strength and weakness of his studio masters. They offer everything you need, but never throw it aggressively in your face (or, well, your ears). There may be a slight emphasis around 1-2 kHz that brings voices and certain instruments slightly forward, perhaps softening adjacent frequencies, but the effect is anything but unpleasant. On the contrary, it adds a touch of realism and presence to the sound.

This relaxed character extends into the treble, which is velvety yet well-extended and rich in harmonics. All the details are present, but always delivered with grace and refinement. I wouldn't call the sound euphonic, but there is certainly a hint of warmth.

Dynamically, performance is very good - superior to the Audeze in some aspects - aside from the bass region, where the lack of a certain bite can make a few tracks feel less visceral than they should. On the micro level (the so-called microdynamics), performance is excellent: the sound remains lively and textured, and every layer of the musical structure, even the most complex, is effortlessly unravelled and presented to the listener. A comparison with the Canon Pro is not flattering in this respect, as those IEMs sound faster and more sparkling, but it's worth remembering that these are two almost diametrically opposed approaches, and IEM technology naturally helps prevent anything from being lost between the transducer and the listener's eardrum.

3D imaging is perhaps the most striking aspect, especially if you're used to sound that feels a bit too “inside your head”: here, the music seems to unfold in a large room, with clearly layered and distant sound planes. It's an extremely captivating presentation, as it comes remarkably close to the experience of listening to good loudspeakers - always a difficult achievement for any pair of headphones. If you're not a fan of the unnatural sensation of sound being “inside your head,” these Fosi may very well change your mind about headphone listening.

This is also one of the reasons why the i5 can be enjoyed for very long sessions without fatigue. Their sound recalls that of various magnetostatic or electrostatic panels, but also brings to mind certain omnidirectional loudspeakers. In short, if you want to listen to a lot of music without the hyper-critical, borderline-paranoid mindset typical of many audiophiles...these i5s are definitely for you. Just music - lots of it - without stress or fatigue.

In the end, for my personal taste, despite a few areas where the Audeze performs slightly better, I preferred the Fosi i5 overall. I found it more balanced, enjoyable, and easy to listen to. Considering the price difference, that says a lot - and it greatly enhances the perceived value for money.

Remarks & Complaints

Construction & Finish.
The level of finish is excellent, the materials are very good and of high quality, the appearance is truly premium, and comfort is excellent despite the weight. The packaging is so luxurious that it makes the more expensive Audeze models seem like products from a much lower tier. I have no real complaints regarding either the build quality or usability.
These headphones are also quite easy to drive without needing extremely powerful, specialized amplification - although their quality certainly deserves a good headphone amp. In terms of sound pressure, even the small Fosi DS2 dongle proved more than adequate, and honestly, even a smartphone output would do. This gives you an idea of just how easy these headphones are to handle, even from an electrical standpoint.
Sound.
The sound is that of an excellent magnetostatic panel - almost electrostatic, I'd dare say. You won't be blasting Rage Against the Machine in all their fury with these, but you will enjoy a natural, lively, precise, and non-fatiguing sound with a genuinely expansive sound-stage. If, on the other hand, you're looking for monitor-style headphones to dissect every last detail - dynamic or otherwise - of a recording, you may want to look elsewhere.

Conclusions

This was an ambitious project - Fosi Audio's first genuinely expensive product - but the result proves this dynamic Chinese company right: they clearly did their homework! These are not headphones for everyone, neither in price nor in sonic character, but they are extremely enjoyable to listen to and offer a very solid value for money considering the technology used and the level of build and finish. Little Fosi's grow up...

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Fosi Audio i5 - open-back magneto-planar headphones

Is Fosi upping the ante?

Foreword

A closer look

Is Fosi upping the ante?

Remarks & Complaints

Conclusions