Fiio FX15 Review: Fiio Breaks New Ground
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Fiio FX15 Review: Fiio Breaks New Ground

Jul 31, 2023

Christopher Coke Updated: Aug 8, 2023 1:43 AM Posted: Aug 7, 2023 3:50 PM ET Category: Hardware Reviews 0

Fiio is a brand that’s impressed us over the years. It has made a point to deliver value with exceptional designs, build, and sound quality. Today, we’re looking at the FX15, a first for the brand. It’s the company’s first-ever earphone to utilize electrostatic drivers. Its late arrival might raise some eyebrows, but Fiio has been hard at work to develop an EST earphone that stands out from the pack. At $799, it’s expensive but only in the middle tier of pricing for this style of IEM. Does it deliver? Let’s take a closer look and find out.

If you’ve been following the audio world at all, you’ve likely already heard of Fiio. We’ve covered the brand extensively over the years and for good reason — or should we say, reasons. It’s one of the biggest players in the Eastern Hi-Fi world, delivering a multitude of products over the years that, by and large, have been positively received. It releases new products regularly, and in some cases quite a bit faster than its competitors. Just as importantly, its products span the gamut from low-cost and affordable to premium and expensive, though nearly always with an eye toward accessibility. It’s a brand that tends to push prices down and increase what you can expect for the dollar, so even if you’re not a fan of every product they release, it’s worth watching them closely.

With that in mind, it’s rather surprising that we’re only now seeing it enter the tribrid (triple driver type, typically dynamic drivers, balanced armatures, and electrostatics) earphone market. Tribrids have been increasing in popularity over the last couple of years and a number of top sets utilize this design. So what took Fiio so long to join the fun?

The company sent along some background information ahead of this review that answers exactly that. In short, the company wanted to make sure that when they did it, they did it right. First off, because electrostatic, or EST, drivers are specialized for treble, they require other drivers to fully cover the frequency range. With ESTs being quite expensive on their own, they wanted to make sure they could deliver an accessible product.

Alongside that, they wanted their drivers to actually be audible so you can clearly hear their benefit. Balanced armatures and dynamic drivers are simply louder, so the ESTs in many earphones are more subtle in their improvements. You can hear them, but the bulk of the listening experience is still from the balanced armatures and dynamic drivers. When you can get great earphones with just those two driver types for literally hundreds of dollars less, making sure you can clearly hear what those specialized drivers are offering is an idea I can get behind.

The FX15 is Fiio’s answer to these concerns. Rather than a more traditional arrangement with one DD, lots of BAs, and an EST or two, it uses a single dynamic driver and balanced armature, and then four electrostatic drivers. It’s a rebalance that occurs before the sound hits any transformer to amplify the sound, so when it finally makes its way to your ears, there is simply more EST and less everything else.

Fiio even went so far as to add an on/off switch for the EST drivers to each earphone. It’s a tuning switch, but rather than changing the EQ as a whole, it literally turns the electrostatics on and off so you can hear the impact they’re making and know exactly what it is your extra money is paying for. Though I’ll explain more in the listening section, the impact is immediately noticeable and it’s the ESTs that lend this set their clarity, detail, and crispness.

Fiio didn’t skimp on the rest of the design, however. The dynamic driver is large at 10mm and coated in Diamond-Like Carbon (DLC) for increased rigidity and speed. It uses Fiio’s S-Turbo acoustic tube waveguide to enhance its bass performance further. The balanced armature is a Knowles ED-29689 and covers the mids and transitions into the highs where the ESTs take over.

The shells are 3D printed using a DLP process that, according to the company, is accurate down to 0.0375mm to help ensure consistent sound between units. Fiio cooperated with the same company utilized by Moondrop and Truthear (and may have previously also — Fiio lays claim to offering the first-ever 3D printed shell, so it’s possible that this may be a longstanding relationship we’re only just finding out about here). The faceplates use a line and contour pattern that’s understated and looks good but won’t attract unwanted attention if you take them out of the house. They’re medium thickness and are contoured on the inner side to leverage your pinna (outer ear) for additional support. They’re quite comfortable.

Fiio also continues its trend of being an industry leader in terms of the accessories you receive with the package. The cable is simply fantastic. It’s an 8-stand, 224-wire cable woven together in a soft rope to avoid microphonics. It connects to each earpiece with extended MMCX connectors protected with stainless steel shrouds for added protection when installing/removing them. On the other end, the cable is modular, with friction-fit 3.5mm (single-ended) and 4.4mm (balanced) connections to accommodate a wider range of sources. Changing them is as easy as unscrewing the shroud, unplugging the current plug, and replacing with with the other.

Fiio also included a nice leatherette case made with a hard protective shell. It latches closed with a powerful magnet to safely travel in a bag and is finished in blue and brown leather, looking quite dapper. The interior is lined with soft fabric and has two chambers to protect the ear pieces from jostling around in transit.

There are also masses of ear tips to choose from, so finding a proper fit shouldn’t be an issue for any listener. There are a whopping 18 pairs of eartips included, with specialized sets for vocals, bass, and balanced sound signatures, as well as memory foam tips and bi-flanges. In separate baggies are three pairs each of premium SpinFit eartips and Fiio’s own HS18 tips. I personally found the SpinFits and HS18s to be the most comfortable, but as always, it’s worth trying each to see which works better for your ear.

Also included in the box is an MMCX quick removal tool, a magnetic cable cinch, and an earphone cleaning tool. It’s a generous package and right in keeping with Fiio’s other products. Other company’s selling expensive audio products need to pay attention: this is how it should be.

Graph and Measurement Credits: Ian Fann via Squig.Link

One of the goals with the FX15 was to make it easy to drive, and Fiio succeeded with that. You don’t need special gear to achieve a good volume on these, a simple dongle will do. I conducted most of my testing with the Fiio M15 ESS since it was such a natural fit, but it also worked fine with my $15 CX Pro dongle DAC, so you should be good to go with most sources.

What’s important to note here is that the FX15 seems particularly influenced by the source you’re using. If you’re using something warmer, like the Questyle M15, that warmth comes through more readily than many other earphones, and tribrids in particular. Understanding that, I do recommend pairing these with something that’s neutral or slightly warm. The ESTs add a bit of brightness that could be a bit much for treble sensitive listeners and a good source can balance that out.

Starting with the bass, I found it to be well-extended and textured. There’s plentiful sub-bass here, enough to handle everything from EZ Mil’s Realest and Church by Tom MacDonald to Neurotica by Polyphia. The bass is very, very tight and has a high-resolution texture. Its speed works to enhance listening across genres and even works well for heavy metal with fast double kick drums. It can be impactful and pound, but it’s not an exceptionally bassy set overall and leans much more into the treble than anything else.

With the bass minding its lane so well, the mids are completely unimpeded. Vocals come forward (especially female vocals) and sound natural. There’s a crispness to their sound that can sometimes give singers and instruments a bit of edge cut. That can work well for guitar-driven music but can also make instruments sound a bit aggressive. Welcome to the Jungle by Stage Kids had more of an edge that I’ve heard on that track in a long time, making the slightly overdriven guitars sound more prominent and driving rather than bell-like as I’m used to. Origami by The Surrealist is also especially “plucky” with its finger-picked acoustic guitar lines.

These qualities are a direct result of the ESTs raising the upper harmonics of the notes (aside: each note and sound is a combination of frequencies ringing at once to create one distinct sound, the higher level ones are known as upper harmonics). Given that ESTs are treble-focused and that Fiio wanted to make sure you could hear them at work here like no other, it should come as no surprise, then, that the treble is really where the FX15’s shine.

The high-end on this set is well-extended and dripping with sparkle. The ESTs aren’t subtle here: they’re clearly audible, enhancing the entire treble range, creating a listening experience that sounds exceptionally clear and resolving. Mira by The Surrealist features multiple guitars playing with fast, syncopated picking and it comes through perfectly. There’s absolutely no muddiness. It is crisp and articulate in a way that leaves absolutely nothing on the table. It can be slightly bright with cymbal hits, which could lead to fatigue, but know one and all: this is a treble set and it does it well.

Fiio included a “tuning” switch that enables or disables the EST cluster. Turning this switch off drops the treble so it’s not as shiny or resolving, though remains rather bright. With that switch off, however, the FX15 loses its most defining feature. It’s a nice option to have if you’re treble sensitive and particularly listening experience is too bright, but overall, the set is much better with the ESTs left on.

Taken as a whole, however, I think Fiio has done an excellent job of balancing out its high-end detail with low-end speed and support. The ESTs would lose their charm if not for the bass coming in behind it delivering body, speed, and substance to the listening experience, making it not just high-resolution but also rich.

The soundstage, layering, and imaging are all very good, though soundstage in particular varies from good to great depending on what you’re listening to. The boost to the air regions with the ESTs allow reverbs to hit much better, so tracks and games with atmospheric effects work exceptionally well here. Even without these enhancements, the soundstage is quite wide and makes for an immersive listening experience.

Likewise, positioning and layering are very good here also. The resolution of this set makes perceiving multiple layers natural and easy, drawing them right away and creating space for every note and audio cue.


Magrid Xenns Up ($699): The Xenns Up has a much greater bass focus and traditional V-shaped tuning. The FX15 is more resolving and detail-oriented while the Up is much more about the fun of slammy mainstream music.

Thieaudio Monarch Mk.II ($999): The Monarch Mk.II is one of my favorite earphones of all time and is all around more balanced without sacrificing on details or presentation. That shouldn’t be a surprise considering the Monarch’s much higher price, but it’s notable that if you’re shopping for a hybrid, the MkII is less likely to fatigue you with its brightness. The FX15 hits in the same region for details and its enhanced reactivity with reverb and atmospherics makes it more fun at times, though.

Thieaudio Prestige ($1,299): Two bright, tribrid IEMs! The Prestige is even more expensive than the Monarch but hits closer to the FX15 due to its sparklier tuning. The FX15 handles its brightness better than the Prestige but doesn’t have the same kind of detail retrieval. The FX15 has more crispness to the details in its treble but isn’t as sharp as the Prestige. The mids

For Gaming, the FX15 is a bit hit or miss. The directionality of its sound is there, but depending on the environment you’re in, it can become hazy as environmental reverb comes in. The details can make it sound very high resolution and immersive, and that environmental interplay actually works to its benefit in single-player immersive games (I’m looking at you Baldur’s Gate 3), but for gaming alone, Fiio has better options in its catalog.

The Fiio FX15 is a very unique earphone, which is something that’s getting harder and harder to say these days. There are simply so many options at every price point, that it’s hard for individual pairs to stand out… but stand out the FX15 does. By leaning into its ESTs, it has managed to deliver a bright, highly detailed listening experience that’s also quite fun, and unlike anything else at this price point. It won’t be for everybody but it’s definitely worth hearing for yourself and seeing explicitly what all of those ESTs are up to.

The product described in this article was provided by the manufacturer for evaluation purposes.

Chris cut his teeth on MMOs in the late 90s with text-based MUDs. He’s written about video games for many different sites but has made MMORPG his home since 2013. Today, he acts as Hardware and Technology Editor, lead tech reviewer, and continues to love and write about games every chance he gets. Follow him on Twitter: @GameByNight

SpecificationsFiio FX15 - First Impressions and Key Features Fiio FX15 - Listening Impressions ComparisonsMagrid Xenns Up ($699): Thieaudio Monarch Mk.II ($999): Thieaudio Prestige ($1,299): Overall Impressions and Final Thoughts8.0GreatProsCons