FiiO FX15 Review featured image

FiiO FX15 Review



The FX15 doesn’t require lots of power but the source is well noted since this is a highly revealing set. However, that’s not their main focus which seems to be their well-pronounced high frequencies so use sources with clean treble.

There’s a test that I perform that’s easy to do which is to put the volume to zero and while raising the volume, listen for frequency imbalance. Particularly for frequencies that are produced before all others.

If the high frequencies were too prominent then they would be audible first and that didn’t happen with this set. So that can only mean that the forwardness is perceived since the test proves that the drivers are in equilibrium in frequency output tuning.

FiiO FX15 paired with KA5


Besides pairing the FX15 with the Diablo, the NEO, and FiiO’s portable gear I wanted to see how a low-power output device would work with the FX15. So, I pulled out the ddHiFi’s TC35C and it worked out surprisingly well.

FiiO’s Q11 also paired formidably in combination with the FX15. The Q11 tends to sound generally the same regardless of what the equipment source is and in combination with the FX15, it makes a versatile setup.

I would not use the FX15 directly on a phone since most models are incapable of reaching a 90-decibel SN ratio and the FX15 has a high dynamic range capability. So that would decapitate this set and hide some of their capabilities.

The FiiO FX15 is a very good performer and I would also stick with anything that has a low noise floor since it can produce hiss or best said, reveal its presence.

FiiO FH9

Select Comparisons

FiiO FH9


The FH9 was the previous top dog within the FiiO IEM lineup but some argue that the title belongs to the FD7. However, we’re talking apples and oranges here since the FH9 has a hybrid multiple-driver array and the FD7 relies on a single dynamic driver.

The FH9 accessories inclusion list is longer since they come with 2.5mm connectivity along with 3.5mm and 4.4mm connectivity as well. They also come with a tri-set of output nozzle filters that change their overall tonality but found them to be disruptive of sound quality and stuck with the stock neutral filters.

The FiiO FH9 has a robust list of internal drivers and a 7-driver array. The most notable is the 13.6 dynamic bass driver which seems to be larger compared to the average IEM’s driver implementations.

But that doesn’t mean that the FH9 is a bass monster because it has 6 BA drivers to compete against. To be honest, I enjoyed the cleaner presentation in bass from the FX15 over the FH9 bass response.    


There is a thesis and anti-thesis concept at play here design-wise. The all-metal design is a neat concept but some might think that the metal will feel cold and that the metal construction might add weight. Both beliefs would be incorrect.

The FH9 Titanium shells absorb and retain heat very well, so as soon as you put them on the material adapts to your body temperature quickly. Additional comfort comes from the fact that the FH9 shell barely touches my inner ear and I mostly feel the tips.

My initial feelings about the overall design and appearance of the FH9 shell were robust but plain Jane in appearance. But it’s a timeless design and the more I look at them, the more the design agrees with my taste.


I used the same cable that came with the FX15 on both sets to be fair but both cable assemblies look eerily similar and just might be the same assembly. I also used the same narrow-bore black rubber tips.

There’s certainly an increase in forwardness in the FH9. The FH9 is also more efficient and can run on half the power I need to reach a similar volume level with the FX15 set.

The FH9 bass response is also neutral even though the dynamic driver is quite large at 13.6mm and it seems that it lost some resolution versus the FX15 bass which uses a smaller but more refined driver. The bass is surely tighter on the FX15 set.

The high midrange output is the section that gives the FH9 its forward presentation over the FX15 but is just as smooth, although some might argue that the lower output within those bands on the FX15 is what gives them that smoother perceived response over the FH9.

The high frequencies are cleaner and more present and have an airy character on the FX15 more so than on the FH9. So FiiO accomplished what they set to deliver. There is a more abundant spatial presentation of high frequencies on the FH9 but they lose some of the definition portrayed by the FX15.

Kinera Imperial URD Review

Kinera Imperial URD


If one set closely assimilates the FH15 in this comparison then the Kinera Imperial URD fits the shoe because the design particulars are similar in that they both were constructed from resins and employ a hybrid multi-driver array.

Another similarity is that the URD also relies on Sonion Electrostatic drivers for its top end but they’re used less prominently. The reason is that the URD has only two Sonion drivers while the FX15 uses four in each shell.

By the use of series/parallel connections, FiiO managed to unload the individual driver’s responsibility to produce, and that in turn allows the tuning to be more moderate on each driver and not overload any particular driver within the array.

To give credit to Kinera where it’s due, they did use a 32873 driver that according to the spec sheets sits in a higher tier over FiiO’s 29689 and seems to have better specifications.


The URD does use similar Sonion high-frequency drivers but, as stated, it seems to use only two instead of four drivers within its Sonion tweeter array. So that makes the URD a more midrange prominent IEM because it uses a more robust midrange cluster.

The URD shell is similarly made from a medical grade resin but uses .78mm dual pin connectivity instead of the MMCX connectors that FiiO uses. However, I have no complaints about the FiiO MMCX connectors because I have yet to receive a FiiO IEM with an intermittent or problematic MMCX connector.


The URD takes a different approach sonically. It projects a wider, less focused presentation and it takes on an even flatter presentation. To veer off that neutral presentation the URD accepts a small boost but not such an ambitious one.

The URD caters mostly to detail-oriented listeners who prefer micro production over the fun factor that the FX15 can deliver especially when boosted. However, some might perceive the URD as being the more natural-sounding set and most likely consider it to be upfront in tonal realism.



The THIEAUDIO Oracle MKII is an IEM with a versatile sound signature, similar to the FX15 that can take a boost and become a party animal but still presents the ability to produce a delicate side and produce a balanced output.

The Oracle MKII bass response can dish out the goods. But these can also produce some sweet highs since they also employ Sonion EST drivers.

The Oracle MKII has a similar tribrid array consisting of a 10mm LCP dynamic driver, a dual Knowles BA combo plus the Sonion tweeter combo in a 1+2+2 setup.


Both these IEMs are similar in design. They both employ a resin shell and a decorative backplate. To be honest, I like the design pattern on the MKII backplate best. I prefer a dark theme over a light theme.

There were a couple of THIEAUDIO IEMs that had a smooth output bore and I often found that the tips would stay inside the ear canal since they had nothing to grab onto. That happened to me with the Legacy 5. But the Oracle MKII has a prominent ring on the tip that corrected that issue.

One aspect that the Oracle MKII has going for it is that it comes with a cable set that includes three types of connectivity. It includes the 4.4mm, the 2.5mm, and the 2.5mm connectivity. However, the FiiO cable seems more robust and uses more wire strands per side.

But at the other end of the coin, you get less tip inclusion with the Oracle MKII. The total accessories package does lack quantity but you still get a decent storage case.


The Oracle MKII is a fine contender if you’re looking for something that has more bite within the overall sound presentation. This one gives off a slight V-shaped tune but remains with a good level of balance and a good representation of the overall frequency spectrum.

The MKII 10mm bass driver is capable of some serious energy and slam and could be best if you use a low-power source since it’s a highly efficient set, more so than the FX15.

The only problem I detected within the Oracle MKII’s sound signature was an overly aggressive 7k peak but when you tame that peak, the set becomes quite remarkable.

The Oracle MKII was marketed as an IEM with studio-quality sound but it has an undeniably fun tuning. However, so also the FX15, and perhaps you’re looking for a cleaner treble production. In that case, the FX15 takes the title in this roundup by a nose.

FiiO FX15 EST retail box

Our Verdict

The FiiO FX15 is a very good IEM. My only critique of them is a small one. FiiO could have easily omitted the electrostatic driver on and off switch and saved on time, implementation, and build costs.

The FX15 is for the high-frequency lover and I doubt any high-frequency lover would prefer their general tuning with a lower treble output than their stock presentation. I mean, why would you invest in a treble first set to then shut off those lovely highs that the FX15 is capable of producing?

But the bottom line question still arises. Is the FiiO FX15 the new top dog within FiiO’s current IEM lineup? It certainly is. They’re fun and pleasant to listen to, they come well-accessorized and are versatile as far as synergy and overall sonic versatility go.

FiiO FX15 Technical Specifications

  • Headphone type: Dynamic BA Electrostatic Tribrid IEM
  • Wear method: in-ear, around the ear
  • Drivers: 1 Knowles Balanced armature/1 10mm Dynamic/ 4 Sonion Electrostatic
  • Frequency response: 20Hz – 40kHz
  • Impedance: 24Ω @1kHz
  • Sensitivity: 103db/ mW@1khz
  • Cable: 8 cables totaling 224 strands of high-purity silver
  • Cable length: about 1.2m
  • Unit weight: about 6g (excluding cable)
  • Earphone connector: Expanded MMCX
  • Audio plug: Twist lock interchangeable plugs

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