FiiO FX17

Premium Electrostatic Excellence from FiiO

Note: this review was originally planned to be one in a series of high-end reviews to coincide with Munich High End, but sadly, the FX17 was stuck in customs until after I returned from Munich. I find it interesting that many of these high-end audio products share some similarities, and the FX17 shares some of the high-end attributes with the 2 Meze flagship headphones that I also reviewed in this series just before Munich.

The FiiO FX17 represents the company’s flagship electrostatic in-ear monitor, building upon the foundation laid by its predecessor, the FX15, but it is significantly more expensive at $1800. Does it live up to its price?

Having rescued the FX17 from customs and now having spent several weeks with it, I’ve found it to be an impressive technical achievement mostly across the board. Especially for those who like a warm, rich, and detailed sound signature, this is a very high-end IEM with a price point that matches its status.

What makes the FX17 particularly noteworthy is its implementation of electrostatic drivers. By utilising, 8 EST per IEM, I believe FiiO is letting the EST’s shine in the treble region rather than a more typical implementation which ‘blends’ the EST with other driver technology, where maybe a BA driver is used with the EST’s to get decent treble volume, this is not the case here, and it is probably the best treble I have heard in an IEM.

So, with 8 EST per side I almost imagine this IEM was designed like an expert chef would design a special dish, maybe adding a spoon of seasoning, tasting it and then realising it needs more and adding another spoon and repeating this process a few times. I can imagine the design team starting with maybe 2 EST and realizing they needed more and more EST’s until they get to 8 per side, this of course drove up the price, but I guess in a flagship you need the absolute best of everything.

Anyway, before I delve into the sound, let’s look at the very premium unboxing experience and accessories.

Unboxing and Build Quality

The unboxing experience of the FX17 is befitting its premium status, but having previously reviewed a few FiiO flaghsips, like the excellent FH19, it is a similar yet impressive experience:

Minimal information on the back of the box:

Removing the other sleeze reveals the inner box:

Opening this reveals you finally get a sense of the FX17’s:

The FX17 comes with an impressive array of accessories which you access via drawers in the box:

• FiiO FX17 IEMs
• Cable with a triple adapter set (3.5mm, 4.4mm, and USB-C with PEQ functionality)
• Extensive selection of ear tips in various sizes and materials
• Premium carrying case
• Documentation and warranty information

The extremely premium cable is underneath the circular FiiO ‘coaster’:

There are various Earips including a whole selection in a box:

Another drawer contains the adapters for the cable - more about these in a bit:

The carry case is in another drawer:

And this box contains some more eartips, a clip and a MMCX release tool:

The build quality of the FX17 shells is exceptional, with premium materials used throughout and lots of little touches you only appreciate after a while.

The shells feature a sophisticated metalic design that not only looks premium, but they are very large, so the FX17 is not for those with smaller ears. But for me, they worked very well with a sculpted shape that fixes perfectly in my ear.

The included cable deserves special mention for its excellent construction and premium feel. It’s flexible yet durable, with high-quality connectors that inspire confidence in long-term reliability. Often flagship cables are too heavy ( as companies chase the specs over comfort), but not here this is a great cable:

Like all FiiO flagship models it comes with MMCX connectors:

The triple adapter set is particularly noteworthy, offering the versatility of 3.5mm, 4.4mm, and USB-C options.

The 4.4mm adapter:

I love the style of the adapter:

The usb-c attached to the cable:

Note: I think the USB-C adapter with built-in PEQ functionality is a fantastic option and one that I would love to see in more IEMs, allowing users to fine-tune the sound signature to their preferences.

You simply screw the end of the adapter to remove it:

This is the other end of the adapter:

I love how small the usb-c adapter is. It is pretty amazing that this has a decent DAC with DSP in something this size:

Comfort comparison with the FH19

As I mentioned above, The FX17 features a large but ergonomically designed shell that contours well to my ear.

Here is a comparison with the FD15 and the FH19:

Note: The FD15 is better suited to smaller ears.

While the FX17 is a more premium-looking IEM with that seamless metalic shell, I did find it interesting that it shares almost exactly the same ergonomic shape as the FH19 even down to the width and length of the nozzles:

I like that FiiO obviously did significant research on this shape and are re-using it in these exceptional IEMs.

Overall, I am very impressed with everything provided with the FX17, so lets get on the sound.

Sound Quality

I mentioned earlier that I found it interesting (and coincidental) that some of the other headphones I reviewed in this Munich High-end series had similarities with the FX17. They share an extremely high-quality build as mentioned above, but more interesting is that I feel the FX17 has a similar “warm” yet detailed sound signature that is typical of Meze flagship headphones.

But I think it is the implementation of electrostatic drivers for the treble frequencies is particularly impressive, offering exceptional detail and extension without the harshness that can sometimes plague hybrid IEMs, the crossover implementation between the drivers is impeccable. The treble performance here sort of reminds me of one of my other favourite headphones, the Mod-house Tungsten. But let’s get into the details.

Bass

The bass response of the FX17 is rich and full-bodied, providing a warm foundation to the overall sound signature. There’s substantial impact and weight to low frequencies, with good extension into the subbass region. The mid bass offers a satisfying and musical presentation that works well across various genres, but those used to a ‘Harman’ tuck might find the bass a little muddy.

This robust low-end performance becomes immediately apparent when listening to tracks like Thundercat’s ‘Them Changes,’ where the syncopated bass line carries both the rhythmic complexity and harmonic richness that the FX17 handles with aplomb. The headphones deliver the track’s iconic bass guitar with impressive texture and body, allowing each note to resonate with proper weight.

Midrange

The midrange presentation is rich and full, with a slight warmth that gives vocals and instruments a natural, organic quality. Male vocals have appropriate weight and body, while female vocals maintain clarity and presence without becoming harsh or strident.

Instruments like guitars, pianos, and strings display good timbre and texture, with enough detail to convey the nuances of performances without becoming analytical. The midrange strikes a good balance between detail retrieval and musical enjoyment, making it well-suited for extended listening sessions.

The FX17’s midrange prowess shines particularly well on tracks like Norah Jones’ ‘Come Away With Me,’ where the interplay between her intimate vocals and the accompanying acoustic guitar creates a perfect showcase for the IEM’s organic presentation.

Treble

But I believe the majority of the research and design of the FX17 was for its treble performance, and it shows. Unlike the previous FX15 model, the FX17 uses these drivers in a more subtle and refined manner, resulting in exceptional detail and extension without ever becoming fatiguing.

High-frequency instruments like cymbals, hi-hats, and violins have a natural shimmer and decay, with excellent micro-detail that adds to the overall sense of realism. The treble extends well into the upper registers, contributing to a good sense of air and space around instruments.

What’s particularly impressive is how the FX17 manages to deliver this level of treble detail and extension without ever becoming harsh or sibilant. It’s a delicate balance that many electrostatic hybrids struggle to achieve, but FiiO has managed it admirably here.

The sophisticated treble tuning of the FX17 becomes particularly clear when listening to Steely Dan’s ‘Aja,’ where the complex arrangement’s layered percussion, jazz guitar harmonics, and saxophone work create a demanding test for any IEM’s high-frequency capabilities. The way the FX17 handles the intricate drum work throughout the track is exemplary. Each hi-hat strike maintains its crisp attack and natural metallic ring without ever veering into that aggressive brightness that can make extended listening uncomfortable.

Soundstage and Imaging

The FX17 presents a reasonably spacious soundstage for an IEM, with good width and adequate height. Imaging is precise, allowing for accurate placement of instruments and vocals within the sound field. The separation between elements in complex mixes is handled well, maintaining clarity even during busy passages.

The sense of space and dimensionality is enhanced by the excellent treble extension, which adds air and ambience to recordings. While it doesn’t quite match the holographic presentation of some top-tier open-back headphones, it performs exceptional soundstage for an IEM.

Specifications and Measurements

• Driver Configuration: 10mm dynamic * 1, Balanced Armature * 4 and Sonion electrostatic * 8
• Frequency Response: 5Hz-40kHz
• Impedance: 16Ω
• Sensitivity: 106dB/mW
• Cable: Detachable 1.2m high-quality cable with interchangeable terminations
• Connectors: MMCX Connectors

FiiO have lots of extra information on their website, but since I love see diagrams of the internal of audio products, I thought these 2 diagrams that FiiO has put together are pretty impressive:

Measurements

All Pragmatic Audio measurements are done with my KB501X soft ear pinna with a 711 clone coupler and are available here

Frequency Response

The frequency response measurements show that mid-bass warmth and that excellent smooth treble extension:

Note: I added both the Harman and the JM-1 target to the measurement above to show that the FX17 bass, while warm, is nicely placed between both these targets. I also found it interesting that the lovely treble is actually much closer to the JM-1 treble.

Overall, I hope this measurement shows the FX17 has an interesting tuning, it is certainly a fun IEM to listen too.

Note: You should also not forget that the usb-c adapter provides the option for a 5-band PEQ filters, so can be used to tweak that mid-range should you want. e.g. maybe a small -1db filter in the 100hz-200hz region.

Next, I thought it might be interesting to compare it with some other FiiO IEMs:

First with just the FH19:

This shows some similarities in the bass and midrange tuning. Obviously, FiiO are going for a ‘house sound’ for their flagship IEMs, probably another similarity with the Meze headphones I mentioned in the intro.

And adding last year’s FX15, you can see the improvement in the treble; FiiO learned allot for their previous EST experience:

Next I thought I would compare the FX17 with some excellent Kiwi Ears IEM’s that I feel are also well tuned:

Note: You can see that the FX17 is very close to the KE4 exchanging some mid-bass ‘warm’ for a better (i.e. less) sub-bass. The Kiwi Ears Astral, on the other hand, goes for a Harman bass ’tuck’ but all 3 are very nicely tuned IMO.

Distortion

Distortion is mostly controlled even when playing at over 100dbSPL:

And even as a percentage, there is nothing to be concerned about, that 8Khz peak is more a measurement artifact:

Rating

The FiiO FX17 earns a 4-star pragmatic rating based on these thoughts:

1. Sound Quality: Excellent warm, rich, and detailed sound signature with exceptional treble performance
2. Build Quality: Premium construction with high-quality materials throughout
3. Accessories: Outstanding selection including the versatile triple adapter set
4. Value: While the performance is excellent, the $1800 price tag limits its pragmatic appeal and my only real ‘problem’ with the FX17.

As a pragmatic reviewer, I must acknowledge that while the FX17 delivers exceptional performance, but its price point of roughly $1800 places it beyond what many would consider reasonable value. This is not a criticism of its technical achievements or sound quality, but rather a recognition that diminishing returns become significant at this price tier.

For those who can afford it and desire for a premium listening experience, the FX17 delivers excellence across the board. However, for most listeners, there are options available at lower price points that may offer better value, even if they don’t quite match the FX17’s technical treble capabilities.

Conclusion

The FiiO FX17 represents an impressive technical achievement, successfully implementing electrostatic drivers in this hybrid configuration in a way that enhances the listening experience without introducing the harshness or fatigue that can plague similar designs. Its warm, rich, and detailed sound signature provides an engaging listening experience across a wide range of music genres.

The complete package is equally impressive, from the premium unboxing experience to the extensive selection of accessories. The triple adapter on the cable is particularly noteworthy, offering versatility and added functionality that enhances the overall value proposition.

However, at $1800, the FX17 faces the inevitable question of value. While its performance is excellent, it enters a price bracket where diminishing returns become significant. For those with the budget who prioritize a warm, rich sound signature with exceptional treble performance, the FX17 is an excellent option that competes well with other ultra-premium IEMs.

If you have the opportunity to audition the FX17, it’s well worth experiencing its impressive sound quality, particularly its exceptional treble performance. For those who find its sound signature appealing and aren’t deterred by the price, the FX17 represents an impressive entry in FiiO’s growing lineup of flagship audio products.