最終更新日: 2023.08.1

FIIO FX15 Review 〜FIIO’s first EST driver earphone

FIIO’s first FX15 earphone with EST drivers went on sale in China on July 12. Again, we were able to order and obtain the product on the release date, so here is an overview of the FIIO FX15, an introduction to the actual device, and a review.

First, a brief overview: FIIO FX15 is an earphone with 1DD + 1BA + 4EST configuration. This FX15 is the first FIIO earphone with EST drivers. In addition, it has a switch to turn on/off the electrostatic drivers. Also, the shell is 3D printed for the first time in a long time, and is not a metal shell.

FiiO FX15化粧箱

FIIO FX15 – Summary of review

Let me start with a summary. First of all, the weight of the body of the FX15 is lighter due to the 3D-printed shell, and the outer diameter of the earphones is not too large, so the fit is one of the better ones among FiiO’s earphones. Furthermore, the sound insulation is also high, and I would recommend these earphones to those who feel that many EST-equipped earphones have a large number of drivers, which can be a hurdle in terms of wearing comfort.
Next is the sound, and the feature is the treble. This does not mean that the treble are fully up front and play the leading role, but the detail expression of the treble is excellent. The treble allow the listener to perceive even the finest details of sound and air. This makes instruments and vocal voices sound more realistic. These earphones have a different appeal from the type of earphones that diffuse the treble nicely, such as the 64 Audio earphones. The sound balance is similar to that of the V-shape, but the amount and intensity of bass is moderate. If you want more bass, you will need to adjust the earpieces. Also, there is a switch mechanism this time, but the purpose of this function is to turn the EST driver on and off and compare the difference with and without the EST driver, and other than that comparison, there is no play factor by the switch.


  • Good wearing comfort
  • Comparable sound with and without electrostatic driver
  • Smooth connection from bass to treble
  • Excellent detail expression in treble.
  • Treble has a lot of room, and there is no teeth sound (piercing).
  • Realistic sound of wind instruments


  • The bass is subdued and the treble is less piercing, so the sound is not stimulating enough for some people.
  • The attack and sharpness of the sound is low.

FIIO FX15 – Release date and price

Release date: July 12, 2023  Price: US$749

The price of the FIIO FX15 is the highest among FiiO earphones at this time.

FIIO FX15 – Overview


The main features of the FIIO FX15 are as follows.

  • 1DD + 1BA + 4EST driver configuration
  • EST drivers support high frequencies above 20kHz
  • Knowles ED-29689 for mid-high
  • 10mm DLC dome dynamic driver for bass
  • On-board switch to turn on/off the EST drivers
  • DLP-3D printed shell in collaboration with 3D printing specialist HeyGears
  • Ergonomically designed shell
  • Equipped with S.Turbo acoustic technology
  • 224 eight-piece sterling silver cables bundled together

The FX15 features FIIO’s first EST driver, of course, but I think another important feature is that it also has a switch that allows you to turn that EST driver on and off. This is because, as FIIO also explains, the switch on the FIIO FX15 allows you to directly compare how the presence or absence of an EST driver affects the sound of the earphones. The FIIO FX15 is a great advantage to be able to compare the sound of earphones with and without EST drivers, since all earphones with EST drivers are very expensive. Also, while most of FIIO’s recent earphones have metal shells, this is the first 3D-printed shell since FA9. Other than that, the technologies and materials that FIIO has cultivated up to now are applied.

FIIO FX15 – Package

FIIO FX15 同梱物

As with previous FIIO earphones, the FIIO FX15 bundle includes everything you need.

  • FX15 main unit
  • 8-core, MMCX adapter and sterling silver cable
  • 3.5/4.4 interchangeable plugs
  • Ear tips HS19, HS18, Spinfit
  • Earphone cable clip
  • Earphone case
  • Instruction manual
  • Wechat FX15 user group invitation (Chinese version only)

FIIO FX15 – Design and Fitting review


First is the design. This time, the faceplate has a ginkgo pattern. Personally, I like this faceplate design. It is the opposite of the previous SF armor designs and has a fresh feel to it. And according to FIIO’s explanation, the design unifies the image of the sound with the “ginkgo-filled” appearance. As we will discuss later in the sound review, the sound is excellent at reproducing detail all the way up to the ultra-high frequencies, just like a ginkgo tree-lined avenue in autumn, filled with ginkgo above and below, and you can feel every detail of the sound from the low to the ultra-high frequencies, linking it to a sound truly filled with sound grains.

Next is the fit: the FIIO FX15 is the first in a long time to adopt 3D printing. So far, only the FA series (except FA7S) has adopted 3D printing in FIIO’s earphones. Like the FX15, the FA series was also co-developed by HeyGears. Therefore, the FX15 has the same smooth texture and sound insulation as the FA series. On the other hand, the shape of the earphones is not exactly the same as the FA series, but has been updated. Please take a look at the picture below. The teardrop shape has been changed to an inverted triangle shape. Furthermore, while most earphones with EST drivers have a large shell size, the size of the FX15 is about the size of the FA7 with 4BA. This gives less pressure on the ears.

Clockwise from FX15: FA7, FA1, FA9
Clockwise from FX15: FA7, FA1, FA9

On the other hand, the shell of the FX15 is even thicker than the FA9 (6BA). Therefore, the wearing comfort is good, but the shells stick out slightly from the ears. As a reference of this thickness, we compared it with FH9 (6BA + 1DD). That is the photo below. As you can see, the thickness is almost the same as FH9. Therefore, it is better to imagine the size of the shell as FA7 and the thickness as FH9.

FX15 比較3

The next point that affects the fit of FIIO’s earphones is weight, and FX15 weighs in at a light 6.5g (single side only). For reference, FH9, a metal shell that is easy to feel the weight, weighs 12.5g, so FX15 weighs about half of that. The same 3D printed shells weigh 6.5g for FA9 and 5g for FA7. Therefore, FA9 is the closest in weight. For reference, the metal shell FA7S weighs 8g.

I have explained the comparison at length, but as a conclusion, the fit is close to FA7, the shell is light, and the size is not too large, so I think it is easy for anyone to wear among the earphones with EST drivers. Incidentally, I have small ears and it is difficult for me to wear earphones with even a slightly larger outer diameter shell, but I had no problem with the FX15. If I may say so, the nozzle tends to go deep into the ear, so if you are not comfortable with that, you may need to try several earpieces. I used to use size S of HS18, but I needed a smaller size, so I am now using size SS of final Type E for TWS. final Type E emphasizes bass a little, but FX15 itself has moderate bass, so they are a good match. On the other hand, in the case of thick, non-slip, sticky types such as Sednaearfit Crystytal and radius Deep Mount Clear, the nozzle can easily penetrate deep into the ear, causing strong skin contact and friction, which may cause ear pain for some people. final We recommend earpieces with thinner umbrellas such as Type E, which have a good suction to the ear canal that can complement the bass.

FIIO FX15 – Sound review

Listening environment: M15S, K9Pro / Around 10 songs mainly Japanese music / FiiO HS18 ear tips


The point that impresses me when I first listen to the FiiO FX15 is the detail and atmospheric reproduction of treble notes. Especially in songs with high notes played by trumpet or saxophone, there is a sense of realism. If you first listen to a song like “free free free” by the Tokyo Ska Paradise Orchestra and Rira Ikuta or “Lost in Paradise” by ALI BAND in Japan, you will easily feel the charm of the way they sound. In addition, the way the treble tone sounds and resonates is very generous, allowing the listener to feel even the smallest details of the sound. Instead, it is not the type of sound where the high notes are diffused. It is an image where the upper limit of sound ringing is at a higher position. This is a characteristic feature of FX15, and when the EST driver switch is turned on or off, the detail and airiness of the high frequencies changes in an easily understandable way. we felt that one of the attractions of the EST driver is that it gives a concrete sense of what advantages it has.

On the other hand, the volume and intensity of the bass is moderate, and some may find it lacking. The sound balance is V-shaped, but the low bass makes the sound somewhat monitor-like rather than listening-oriented. The strong attack and sharpness of the bass may also be a reason why it is difficult to perceive. However, this makes the connection from bass to treble smoother (more natural), and makes it easier to perceive the detail and atmosphere of the characteristic treble. Although the balance is not such that the highs are in the foreground and play the leading role, the DD and BA are complementary, and the sound is such that we feel the intention is to let users fully feel the appeal and reproduction ability of the EST driver. Whether you have or have not had earphones with EST drivers, we believe you will discover something new if you compare the FIIO FX15 switch on and off.
Lastly, from the perspective of changes from the prototype we listened to at the event, there seems to have been a change in the bass. In the prototype at the event, the bass was a bit more forward, and I was concerned about the boomy fullness, but in the actual production version, the bass has been moderated and is not bad.
Personally, it is tuned very much in the direction I prefer, and for me, who listens to female vocalists with high voices such as ZUTOMAYO and Rira Ikuta, it is very good to hear their treble range in detail. In particular, the detailed nature of the many kinds of instruments such as piano, violin, and guitar in the live version of ZUTOMAYO, as well as the spare way the high tone voice of the vocalist sounds is addictive. Among them, I recommend the live version of “Zanki”; the high tone is diffused in the series of high tones from the chorus at 2:00~ to the end of the song. It has a different charm from earphones. In the standard song, “Aitsura Zen’in Dosokai(EN:Inside Joke)” also gives you a sense of the roominess of the way it sounds, so here is a link to that as well.

【期間限定】ずっと真夜中でいいのに。『残機』(from ROAD GAME『テクノプア』~叢雲のつるぎ~) ZUTOMAYO – Time Left

【期間限定】ずっと真夜中でいいのに。『Spotify “Go Stream” Live』 (ZUTOMAYO – Spotify “Go Stream” Live) *12:28〜からです。

FIIO FX15 Frequency Responce

FIIO FX15 switch ON

FiiO FX15 ON

FIIO FX15 switch ON vs. OFF

FiiO FX15 ON vs OFF

That’s all for the review. Thank you.

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