FiiO is a brand with great expertise in the field of in-ear monitors. Their extensive collection includes many models with various driver configurations and price tags. From the entry level 1DD FiiO JD3 to their previous flagship, the 1DD+6BA FiiO FH9. Yes, you have read that correctly, their previous flagship because the new one is the FiiO FX15. The first tribrid earphone by FiiO to include electrostatic drivers.
Technical
The FiiO FX15 is an 1DD, 1BA and 4 electrostatic drivers, tribrid earphone, the first such made by FiiO.
For the low frequencies, the FX15 features a 10mm DLC dynamic driver, chosen for its high rigidity, high damping coefficient. In order to achieve harmony between the dynamic, BA, and electrostatic drivers, the R&D team specially redesigned the structure of the dynamic driver. A vent at each earpiece helps to relieve the internal pressure and make for a fatigue-free listening experience.
The FX15 adopts the proven Knowles ED-29689 balanced armature driver to handle the mids and lower treble frequency ranges. The R&D team reduced the sensitivity of this BA driver through the shell design and other methods to ensure that the BA and electrostatic drivers output their respective frequency ranges without interference from each other.
The star of the show are the four electrostatic drivers by Sonion that mostly handle the high and ultra-high frequencies above 15kHz. FiiO has added a switch that specifically turns on and off the electrostatic drivers, allowing the user to instantly compare the sound with and without them.
Non Audio stuff
For the design and the construction of the FX15, FiiO has cooperated with the famous HeyGears to create an earshell that is made using the advanced DLP-3D printing method with printing accuracy down to 0.0375mm. The material used is photosensitive resin, which features high impact resistance, providing robust protection for the electrostatic and balanced armature drivers.
The custom-like shape of the FX15 is like a triangle that not only feels comfortable to wear but also securely stays in the listener's ear and offers very good isolation thanks to the mildly extended nozzle. The FX15 is also very lightweight thus offering a great wearing experience that makes it suitable for long listening sessions. The appearance is unique with a design pattern at the faceplate that is beautiful and discreet looking at the same time. The FX15 is one of the most comfortable, beautiful looking and well made earphone FiiO has made up to date.
Cable
The cable of the FiiO FX15 is worthy of a flagship. A well made and easy to handle detachable cable with expanded MMCX connectors for greater connection stability and longevity. It is a high-purity silver cable with 224 total wires separated into 8 strands of 28 wires each. Each wire is independently insulated and the cable features Litz braiding and an outer sheath that is made of environmentally friendly TPU. Furthermore, the cable has interchangeable, twist-lock, 3.5mm and 4.4m plugs. You can find less thick and more lightweight flagship cables but this is a really good one.
Accessories
FiiO is always generous when it comes to the included accessories. The contents of the FX15 package are illustrated in the following photo.
Power requirements and associated gear
The FiiO FX15 (24Ω/103dB) is relatively easy to drive but it scales incredibly well as it has a class leading transparency and mirror-like fidelity that demand the use of high quality sources. If you like a warm sound signature then use a warmer source and vice versa, the FiiO FX15 will always make sure to mirror the unique sound characteristics of every source. For this review I have mostly used the FiiO M15S, EarMen Angel and iBasso DX320.
Audio stuff
The FiiO FX15 has amazing clarity, mirror-like fidelity, class leading transparency and is one of the most refined and resolving earphones that you can buy without reaching the kilobuck categories. The FiiO FX15 combines excellent technicalities with a musical and engaging sound signature that is aided by a balanced tuning that pays equal attention to all parts of the frequency range.
Sub-bass extension is fantastic, the FiiO FX15 doesn't have any problem at faithfully reproducing the first octave without overpowering the rest of the frequencies. The low-end is weighty, punchy and dynamic with realistic contrast and excellent layering. The texture is not that visceral but not lean either, the bass is tight and very fast so it can easily follow the speed of the electrostatic drivers while it is crystal clear, controlled and well defined. The upper bass is slightly emphasized but not that much as to become tonally inaccurate or to mess with mid-range clarity and presence. The feeling is slightly warm, you can use the balanced or bass ear-tips for a mid-bass focused sound, that is suitable for more casual and fun listening moments, or switch to the vocal or SpinFit ear-tips when you need a more neutral bass tuning for critical listening. For an even more neutral bass you can use the FiiO HS18 ear-tips but they will also make the sound too dry, lean and bright.
The mid-range really shines thanks to its tonal accuracy, the harmonic richness and its timbre realism. The FX15 is musical and engaging, the voices are slightly prominent and the instruments play a supportive role without losing their presence and identity. The FX15 might be using only one BA for reproducing the mid frequencies but it is surprisingly articulate, resolving and refined. The texture is just a bit lean but not dry and by no means clinical. The mid-range has a realistic tonality for both instruments and voices without exhibiting any balanced armature timbre. Tonal balance is good, there is an upper mid-range emphasis but not as much as to cause listener fatigue unless you are listening to poorly recorded material.
The treble is delicate, ethereal and refined like a carefully woven spider web that might look fragile at first but it is strong enough to withstand the furious weather elements. Such is the treble of the FX15 which is finely shaped and sleek but still powerful and crisp with solid extension, exemplary transparency and top-notch definition. Sparkling, energetic and airy, shed with sun-bright light but not sharp or piercing, neither harsh or rough and really absent of any metallic timbre.
These are high frequencies at their best, the FiiO FX15 is made for listeners that seek crystalline clarity, class leading expensiveness and deep detail retrieval but at the same time don't sympathize with analytical, overly bright and clinical sounding earphones. I don't like bright earphones but the FiiO FX15 has instantly become one of my favorites despite its undeniably emphasized treble. This is because it is so refined and ethereal that it gets impossible to sound bright or piercing.
FiiO has done an excellent job into driver implementation and succeeded in making sure that the delicate and ethereal sound of the electrostatic drivers never gets overshadowed by the mid and lower frequencies. At the same time, the four electrostatic drivers never act like a spoiled prima Donna who tries to steal the show but they rather work in perfect harmony with the rest, producing an extremely cohesive and homogeneous sound.
The FX15 is open and wide sounding without any traces of congestion. There is plenty of air and space around the performers, positioning accuracy and imaging are exceptional, depth layering is excellent and there is plenty of ambient information that contributes to the overall sense of immersiveness and realism. What happens though is that the presentation is rather intimate, the listener feels as if sitting too close to the performers and the soundstage is mildly lacking in holographic expansion and the feeling of grandness.
The FiiO FX15 is very enjoyable with all kinds of music, especially if you take advantage of the various ear-tips for fine tuning the sound. But the truth is that this set is tailor-made for critical listening to classical and acoustic music. The better the recording and the quality of the source, the better your listening experience will be as this is an earphone that scales incredibly well.
The tuning switch
This feature is rather useless unless you are curious to find out how the FX15 can sound when you mutilate its electrostatic drivers. Switch off the electrostatic drivers to transform the FX15 from a flagship into an earphone that might sound a little smoother and less sharp in the treble but also lacking in treble quality, tonal balance and cohesiveness. One possible situation for using the switch is for listening to really bad and harsh sounding recordings or when you have a hissing source.
Cable upgrade
You can further enhance the sonic performance of the FiiO FX15 with a simple cable upgrade. Readers will already know that I am a great admirer of the Lavricables pure silver cables that I regularly use for reviewing and music listening. The Lavricables Ultimate is a well made and beautiful looking cable with high quality plugs, a soft feeling and great handling. These are not reasons of course to make you swap the already excellent stock cable.
But you can consider trying a Lavricables Ultimate because, subjectively speaking, it slightly enhances the transparency of the FX15, it helps it sound even more natural and refined, especially in the treble, the timbre becomes more realistic and the bass gains in control and definition. The better your source, the more noticable the differences are going to be but still we are talking about subtle sonic enhancements so don't expect something spectacular. Cable upgrades are always the cherry at the top of the cake when the rest of your audio chain is perfectly matched.
Compared to the FiiO FH9
The FH9 is FiiO's previous flagship, a semi-open, hybrid earphone with a very large 13.6mm DD and 6BA. Too many drivers that need a larger housing so the titanium-made FiiO FH9 is bulkier and heavier than the FX15. The fit is still quite comfortable, despite the size, but it really can't match the supreme comfort of the FX15 which is also much more effective at blocking external noise.
The FiiO FH9 has a bass dominant sound signature but it also manages to stay tonally balanced and well defined throughout the whole frequency range. Thus said, the bass on the FX15 is slightly faster and more controlled, a bit faster and more refined with better layering but while it is powerful and dynamic enough, there is no way to match the sheer power, the thundering dynamics and raw impactful force of the FH9.
I find the FH9 as slightly more resolving and refined in the mid-range, the sound is fuller and weightier while tonal balance and timbre realism are more or less the same between the two earphones. The opposite applies for the treble and the higher frequencies where the FX15 is the undeniable champion. Not only is way more resolving and refined but it is also considerably more natural sounding without any traces of metallic timbre. It extends better, it is crispier and more energetic with greater definition and finer articulation.
The FiiO FH9 offers a wider and more expansive soundstage, the presentation is grander and more holographic. There is more free space and air around the performers but the FX15 is doing much better with ambient information and positioning accuracy so while it might not be that grand sounding, it is more immersive and communicative.
Conclusion
The FX15 is the most resolving, refined and mature sounding earphone FiiO has made up to date. This is a critical listening machine that still manages to stay musical and enjoyable with all kinds of music. A living example that frequency measurements don't always tell the truth. A seemingly bright earphone that doesn't sound bright or piercing at all and maintains an excellent sound balance throughout the whole frequency range without causing listening fatigue. The FX15 is the most expensive earphone ever made by FiiO but it still retains the company's unprecedable price to performance ratio. This is not the end of the road but someone must spend considerably more money to get something better than the FiiO FX15 which offers flagship level performance without the flagship price tag.
The review sample was kindly provided free of charge.
The price of the FiiO FX15 is $749 and you can buy it from FiiO.eu