FiiO F9 Pro Hybrid Triple Driver IEM - Reviews
Pros: Detail, wide soundstage, separation, imaging, comfort, accessories, airy, build and finish
Cons: Maybe a bit too bright, included tips are on the small side, unforgiving on badly recorded audio
I'm an Audio-Technica fan. In fact, it was my chance encounter with Audio-Technica's IM70 that led me down the wallet busting rabbit hole that high performance audio is.
Over the years I've collected various bit of AT gear like the M40x, E40, LS70 and MSR7.
Although the MSR7 is a great pair of cans, wearing them in the heat of the Australian summer can certainly strain the relationship.
So, off I went to Sydney's premiere headphone store, Minidisc, in search of something more portable, and hopefully, a bit cooler on the ears.
I tried the Etymotic ER3 and the ATH-LS200. Both sounded muffled and congested with little to no sparkle in the top end (yes, the MSR7 does ruin everything else for you). I was about to buy the ATH-M60X when I remembered the F9 Pro. I had a quick listen and, well, they live in my house now.
They are like mini MSR7s with very similar signature.

Packaging (AKA: Look at all those goodies!)

Inside the box you get 4 different kinds of tips, each with 3 pairs (S/M/L).
These are tip for enhancing voice, balance, bass and foam tips that reduce treble and enhance bass.
The changes are subtle but noticeable.
Perhaps I have freakishly large earholes, but most tips are way too small for me, except for the large bass ones.
Also in the box, you get two carry cases. A soft fabric pouch and a hard, waterproof plastic case for when you take your F9 Pros scuba diving with you, I suppose.
Inside the soft pouch you'll find two MMCX cables. One standard 3.5mm cable with a remote control and the word "Pro" written on it, in case you forget which F9 version you bought, and a braided balanced one.
Also, if you look carefully, you’ll find the actual IEMs sitting snuggly in a foam block. Remember not to throw these away as you might need them later on.

Physical Attributes (AKA: There's a metal alien bug in my ear and I'm cool with it)

The F9 Pros a completely made of aluminium with decorative ripples across the body of the IEM. It feels sturdy and it's all finished with a very high degree of polish. The metal grey colour looks elegant and serious, never betraying the fact that you're a middle aged man listening to Kyary Pamyu Pamyu.

These guys are tiny. Pictures don't give you the sense of scale. Sure, they are no Etymotics, but compared to my ATH-E40, these are practically microscopic, and with small size comes comfort. Oh, these boys are comfy!
I have worn them all day at work without the slightest hint of heat or discomfort. Even the dreaded over-ear wire didn't bother me.

Sound impressions (AKA: How much room is inside these thing?!)

I’m not going to give you a detailed breakdown of frequencies such as treble, bass, etc... because it means little to me. I’ll instead describe what I hear.
The first thing to hit me was the soundstage, it's bloody massive! There's a real sense of positioning and scale unlike any other IEM I've heard (mind you, I'm no expert). I had no idea an IEM could create such an expansive soundstage, not at this price anyway.

But what about the sound?
It’s an MSR7. That's about it.
Oh, you haven't heard the MSR7?
Well, it's bright and detailed with none of that mid bass hump that most consumer headphones have these days, and this is what the F9 Pro sounds like.
Voices, instruments and positioning is very easy to determine and it all sounds pretty natural to me with a real sense of air and presence.
Okay, maybe the mids are recessed, it's not as forward as the MSR7, but they do sound more natural. Unfortunately the sense of distance works against the F9 Pro when used in public as the voices seem to get lost.
There's no bass bleed in or distortion. Although it may appear bass light on your first hearing, bass can go pretty punchy and deep.
My only issue is the intensity of the treble. Depending on the tips you're using, It can pick up sibilance on badly recorded audio, like the MSR7, but harsher and more piercing. With the Bass and stock tips, it can be quite uncomfortable.
It doesn't happen all the time but if you're sensitive to sibilance, you can try the included clear silicon (vocal enhancement) or foam tips which tone down the highs a bit and brings more thump to the bass.
Another option is to get Comply T500 tips which get rid of sibilance completely. You do lose some sparkle though, but mind over matter. If you don't mind, then it doesn't matter.

Final thoughts

Is it perfect? Of course not. The treble is hot, most of the tips will get no use and some will want more bass, but then again, is there a perfect IEM?
What the F9 Pro is though, it's amazing value. It blew away some IEMs twice its price with its clarity and soundstage. At no point was I left wanting for something more. Your mileage may vary of course, but the next time you are IEM shopping, give the F9 Pro a listen, you may be surprised.


I have recently revisited my F9 pro and could not find much value compared to CCA C16 and CCA A10 for instance.

It would be great to see such comparison , in my opinion, while talking about the "value".
Pros: Great sound quality
Cons: Dodgy build quality and quality control
Having use the Fiio F9 pro for almost a year, and having to return it for repair 3 times already,twice for the earpiece cracking open, and once for a gaulty driver, I have to say that i cannot recommend this iem to any who expect a quality headphone woth solid build quality.

If i am to rate this iem by its sound quality alone, a solid 4 out of 5 star
Pros: -Treble-oriented, clear Mid and Bass, smooth transition
-Good soundstage
-Bang for the buck
-Very nice design and perfect comfortability
-Perfect upgradable for beginner
Cons: -Bass is a bit weak
-Might look small on big ears
-Some users complained feeling fatique

F9 Pro Specs
  • Headphone type: Hybrid IEM
  • Frequency response: 15Hz-40kHz
  • Drive type: 1 dynamic + dual balanced armature drivers (Knowles)
  • Impedance: 28Ω
  • Sensitivity: 106dB/mW
  • Cable design: Detachable with standard MMCX connectors
  • Cables: (2) - 1.2m 2.5mm Balanced + 1.2m 3.5mm Single Ended
  • Jacks: 2.5mm TRRS right-angled gold-plated / 3.5mm right angled gold-plated
  • Weight: approx 21g
  • Casing: Anodised CNC aluminium alloy

If you are reading this after owning FiiO FH1 and considering an upgrade, please feel free to keep on reading.
If you are considering this is as a first start, I would like to suggest having a look at my review on FH1 first:
To quickly remind my background:
I have been into music world for about 15 years. At first I picked up mostly pop, and that was during the golden era of boy-bands like: NSynce, Boyzone, Backstreet boys, Westlife, the Moffatts,… you name them. After one or 2 years later I was so much into Hip-hop, RnB. Later on, high-school, I started playing the guitar in order to impress a girl in class. Since then, I was so much into Metal music, I did play in a local band and we covered bands like: As I lay dying, Parkway Drive, August Burns Red, Metallica, … as well as writing our own songs. As for my main job, I studied mecha-tronics, which part of it is electronics, therefore, I have quite amount of knowledge about electronic signals.
So, my point is that, I have been listening to a wide variety of music, a kind of a play-for-fun musician, and electronics engineer, I hope my review will somewhat make sense to you.
Before I start, please be aware that I believe most headphones reviews are subjective because the ability to sense the music is different from people to people. Believe me, I have a friend who cannot tell the different between $2 and $1000 headphones while listening to them. Even, when you are using the same headphones, the bass will sound different between having the ear-tips well-fitted or loose in your ears. You can try that by yourself and will realize the different right away.

-Player: PC, Xiaomi A1 with USB Audio Player Pro
-DAC: FiiO Q1 Mark II
-Amp: FiiO A3
-IEMs: FiiO FH1, F9 Pro (With RC-MMCXB cable), KZ ZST (With KZ upgrade cable), KZ ZS10 (With KZ Upgrade cable)
-Eartips: acoustune aet08, spinfit cp240 twin blade
-Cable: FiiO L17 to connect DAC and AMP
-iFi ear buddy

-2002 - Aerosmith - O, Yeah! Ultimate Aerosmith Hits [SACD DSF]
-Eluveitie - Evocation II - Pantheon (2017) Hi-Res 24 bit
-Dire Straits - Brothers In Arms (1985) 2014 SHM-SACD-DFF
-Parkway Drive - Reverence (2018) [24bit Hi-Res]
-Linkin Park - Hybrid Theory [24bit Hi-Res]
- Nightwish - Decades (2018) [24bit Hi-Res]

Package, Accessories, Design and build quality
Thanks to previous reviewers, you can pretty much see what is inside the package.
For aesthetic purpose, I think the cable is a bit boring with the black color. The RC-MMCXB with transparent color is more awesome in my opinion (But of course no complain about it because black will suit most people)

Fit, Isolation, and comfort
F9 Pro size is very similar to FH1 (Which is good in terms of Fit, Isolation and comfort).
You can have a look at my review for FH1 in terms of Fit, Isolation and Comfort.
In conclusion, similar to FH1, F9 Pro is a very comfortable piece of iem, especially for those who wants to sleep with them on.

I will compare F9 Pro with FH1, as I already confirmed in the FH1 review, FH1 is a very standard piece of earphones to start your audiophile path. Therefore, I will use FH1 as a baseline.
First of all, please have a look at the graph below:

Sub bass (20-60Hz): The deep bass produced in this range is usually felt more than it is heard, providing a sense of power. Many instruments struggle to enter this frequency range, with the exception of a few bass heavy instruments. However, both FH1 and F9 Pro can handle well. But, between the 2, FH1 is the winner with deeper bass. Just play any rock song, I did the test with Linkin Park - Point of Authority (Hybrid Theory album), you can feel the rumble, the depth of the sub-bass on FH1 very clearly. Not that F9 Pro cannot rumble but it is a bit dampened. This test is proved to be true by looking at the graph above, FH1 sub-bass average around 120 dB (while F9 Pro around 108 dB). You can feel and hear the "uuuw" (boomy) sound with FH1 very clearly.
Bass (60-250Hz): The bass range determines how fat or thin the sound is. The fundamental notes of rhythm are centered on this area. The frequencies around 250 Hz can add a feeling of warmth to the bass without loss of definition. Again, FH1 still feel more punching than F9 Pro as well. This also stated in the graph.
Low Mid (250-500Hz): The low midrange contains the low order harmonics of most instruments and is generally viewed as the bass presence range. Boosting a signal around 300 Hz adds clarity to the bass and lower-stringed instruments. Too much boost around 500 Hz can make higher-frequency instruments sound muffled. Fortunately, both FH1 and F9 Pro does not have this matter, with all the Linkin Park's songs, I can hear very well the Bass (Guitar bass and snare) and Low Mid (Guitar Riff).
But, the strength of punching sound of FH1 is also the weakness here. There is no smooth transition between bass and mid in FH1. While F9 Pro totally fixes this matter. Together with the guitar riff, F9 Pro makes it sound smoother and more natural. Just pick any song of Nightwish, you can understand what I am talking about, the guitar riffs sound very smooth, clean, clear and natural. For this range, F9 Pro is the winner.
Mid Range (500-2k Hz): determines how prominent an instrument is in the mix. Boosting around 1000 Hz can give instruments a horn like quality. Excess output at this range can sound tinny and may cause ear fatigue. If boosting in this area, be very cautious, especially on vocals. The ear is particularly sensitive to how the human voice sounds and its frequency coverage. I think we have a draw here, both are very warm and very comfortable to hear, vocals and instruments are clear, not mixing with each other.
In my review for FH1, I did say try the song Mama Kin of Aerosmith, around 2:30, you will hear a series of pattern, end of each patterns there will be a “crash cymbal” sound. you can hear the details of the crash cymbal on FH1. And on F9 Pro, you can hear as well, and you can hear the upper mid range of the crash cymbal which I will talk more below in upper range.
Again, the graph shape of FH1 and F9 Pro are similar. You can see the drop in dB at 1k Hz, this avoid the horn like as mentioned above.
Upper Range (2k-4k Hz): Human hearing is extremely sensitive at the high midrange frequencies, with the slightest boost around here resulting in a huge change in the sound timbre. The high midrange is responsible for the attack on percussive and rhythm instruments. If boosted, this range can add presence. However, too much boost around the 3 kHz range can cause listening fatigue.
I did mentioned try the song Mama Kin of Aerosmith, around 2:30, you will hear a series of pattern, end of each patterns there will be a “crash cymbal” sound. When you hear the crash cymbal, with FH1, you count 1..2... then the sound dampened. But with F9 pro, you can count up to 1..2..3..4 --> This prove that F9 Pro has more depth in the the high side (I believe this is the benefit of 1 more Armature driver)
The same for both FH1 and F9 Pro, there is a drop in dB at 3kHz to avoid fatique --> Very well tune FiiO.
Presence(4k-6k Hz): The presence range is responsible for clarity and definition of a sound. It is the range at which most home stereos center their treble control on. Over-boosting can cause an irritating, harsh sound. Cutting in this range makes the sound more distant and transparent.
We see a little boost at the middle of this range for both FH1, F9 Pro. The boost is very nice, helping the vocals to be a bit closer, creates the presence, makes you feel like the singers are next to you. And the boost is very dedicated that did not make the sound too harsh.
Also, if you read my review for FH1, I did complain about the "not so impressive" soundstage because FH1 is a bit bass-oriented. But please remember when you go to a live concert, how is the set up? Normally drummer will be the furthest, then the guitars (keyboards, flute,... if available), then vocal is the closest. Therefore, if any system can create this setup will create the best soundstage to you. In FH1, it feels strange because makes you feel like you are sitting next to the drummer, you can see on the graph presence (vocal) at about 110dB but the sub-bass (kick drum) is peak at 118 dB. However, F9 Pro fixed this by damping the low side, pushing the drum a bit further (smaller), therefore, create a better soundstage.
Playing the songs Nightwish - Wish I Had An Angel (Remastered). At the intro, I can hear the high voice, the presence is better than FH1.
So, F9 Pro is the winner at this range.
Brilliance (6k-20k Hz): The brilliance range is composed entirely of harmonics and is responsible for sparkle and air of a sound. Boost around 12 kHz make a recording sound more Hi Fi. Be cautious over boosting in this region as it can accentuate hiss or cause ear fatigue.
I think this is where FiiO made mistake with the boost at 12kHz. Looking at FH1 graph, it is going down at 12kHz, while F9 Pro push it up. So, if you have read all the reviews before me for F9 Pro, all complained that the treble is hot, some feel fatique after listening for a long time. This is the culprit...
Ultra-High (20k-40k Hz): I must admit that this range is out of human ability to hear. However, both show the same shape in the graph so they should be similar.

If this is your first earphones, highly suggested, the sound is a bit on the high side, but this helps to imitate the setup of a band which creates more soundstage. If your gear can boost the bass, F9 Pro will become a beast.
If you are looking for an upgrade from 1 driver, or hybrid 1 + 1 driver, also highly recommend. F9 Pro creates more soundstage, shows more details on the high side but not losing too much on the low side. However, the boost at 12kHz is a small downside which causes fatique to some listeners (Some said they don't have this matter though, so it is different from songs to songs and/or from people to people)
FH5 has just released, some already got their hands on it and said it is the middle of FH1 and F9 Pro. I do expect that from FiiO as well. Since FH5 uses the same big size of Dynamic driver with FH1 the bass should be great, and with the turbo design and more Armature Driver, I expect more details on the high side with more soundstage, and hopefully they are not pushing to much around 12kHz again.
I will make the review for FH5 as soon as I get them in the "World review tour".

-With KZ ZS10:
Even though ZS10 has more drivers, but this is the case where "less is more". For a quick overview, bass of KZ ZS10 is more soft and shallow, I feel no transition between the sub bass and bass (While F9 Pro has a nice transition between the different range). Bass of ZS10 less punchy as well.
ZS10 creates more soundstage by pushing everything far away from you. However, it is kind of backfire, I do not feel the ambient warm sound like F9 Pro. ZS10 sounds colder and thinner.
As for the treble, KZ is way behind FiiO. Between FH1 and F9 Pro, F9 Pro is the winner with more details and depth. However, ZS10 is behind FH1, therefore, way behind F9 Pro for this range. I have proof. Try the example above with the song Mama Kin of Aerosmith, around 2:30. If with FH1, the crash cymbal is like 1..2.., F9 Pro is like 1..2..3..4, then ZS10 is like ..2..2.5.. (If you see what I meant)
Anyway, the soundstage of ZS10 is quite fun, just to say, and the price is cheap.
Bought this... waiting to try it on my onyko xp1A
Pros: Nice balanced sound signature,
Good amount of detail ,
Great build quality and ergonomics,
Lots of accessories (2 x cable, 2x case, etc.)
Cons: The treble sounds a bit hot
Fiio F9 Pro;
A Rich Sound in an Organic Design…


Many of us are familiar with Fiio Products; especially the Portable Audio Players of the X line up like X3, X5, X7 etc. Fiio joined later in to the earphone business with there first IEM that was called Fiio EX1. After the success of Fiio F9, they announced in November 2017 a new upgrade model called F9 Pro, which is the company's second hybrid in-ear monitor (IEM) model, which i will now review for you.


About Fiio:

FiiO is a Chinese HiFi brand that was established in 2007 and has experience in researching and developing countless portable music products of different types, and sell FiiO-branded products through sales agents worldwide. The brand name FiiO is composed of Fi (fidelity from HiFi) and iO (number 1&0), representing the real feeling and convenient life that digital brings to life. Meanwhile, the Chinese “飞傲” is the transliteration of FiiO, indicating the positive and innovative spirit as thriving as spring.


I would like to thank Fiio for providing me the Fiio F9 Pro as free review sample. I am not affiliated with Fiio beyond this review and these words reflect my true and unaltered, opinions about the product.


The MSRP price for the Fiio F9 Pro is 139,99 USD.

Package and Accessories:

The Fiio F9 Pro comes in a small rectangle cardboard box, which is wrapped with a glossy paper sleeve which has some illustrations and specification on about the F9 Pro on it.


This box contains the following contents;

  • 1 pair x F9 Pro In-Ear Monitor
  • 1 x carrying case
  • 12 pairs x Ear tips (3 pairs of foam + 9 pairs of silicone)
  • 1 x 3.5mm single-ended cable with in-line controls
  • 1 x 2.5mm balanced cable
  • 1 x Water-resistant neoprene carrying pouch

The F9 PRO comes with three different types of silicone ear tips ((9 in totals) and one type of foam ear tips in small, medium, and large size, which are very comfortable.


The box contains one waterproof hard case/carry case, as well as a water-resistant neoprene carrying pouch. The hard case is made of a black glossy plastic material that has a very stylish design and a good form factor.


The neoprene zipper pouch is in gray and is quite useful with its small design.



Fiio F9 Pro comes with two types of MMCX (micro-miniature coaxial) connector cables;

The first cable is has an 3.5mm SE (Single Ended) headphone jack with a L-shaped plug that is made of a tin plated cooper material with TPU coating. This cable has a microphone with line-in control.


The second cable has a 2.5mm balanced headphone jack, which comes also with an L-shaped plug. The 4 core cable is made of 5N purity OFC (Oxygen Free Cooper) wire which is has also a black TPU coating.


Cables have nice stylish left and right markings. The left channel is adorned with a splash of blue, while the end of the right channel is trimmed with a red marking for an easy identification of the audio channels. These channel ends also have a spiral texture engraved into them.


Design, Build Quality and Fit:

The shell of the Fiio F9 Pro is made of aluminum and has a very ergonomic design. The outer surface sports a water wave like design which Fiio describes as “Organic Design”. The inside layer of the F9 PRO’s shell is according to Fiio lined with plastic to both better secure the drivers and eliminate internal resonances.


You can find on the inner face of each monitor two bass vents, the L (Left) & R (Right) markings and the model description PRO. The angled nozzle of the Fiio F9 Pro is lipped and sports a fine metal filter on the top. The MMCX connectors have a solid appearance and should last for years.


The noise isolation of the Fiio F9 Pro is above average due the bass vents on the monitor, which are causing to a small amount of noise leakage.


The Fiio F9 Pro is quite comfortable due the relative small size and design shape. I was able to wear it for more than (approx) 2.5 - 3 hours without any discomfort.


  • Driver Type : Hybrid (1 x 9.2mm DD + 2 BA Drivers (Knowles TWFK-30017-000)
  • Frequency response : 15Hz ~ 40kHz
  • Sensitivity : 106 dB/mW
  • Impedance : 28 Ω
  • Cord length : 1.2 m
  • Weight : About 3.76 g/per unit
  • Color : Titanium (with "PRO" mark on the Y-splitter and the earbuds)
  • Detachable Cables : 1 x 2.5mm Balanced and 1x 3.5mm SE Cable with MMCX connectors


More about the Hybrid Driver Configuration:

The Fiio F9 Pro has 2 Knowles balanced armature of the model TWFK-30017-000 + 1 PEK polymer nanocomposite dynamic driver with 9.2mm diameter under the hood.

The Knowles dual balanced armature TWFK-30017-000:

The Knowles dual balanced armature TWFK-30017-000 gives the F9 Pro immense capabilities in resolving every last detail, all in a truly powerful and overwhelming presentation of your music – the way it was meant to be heard.

The PEK Polymer Nanocomposite Dynamic Driver:

The F9 PRO utilizes a dynamic driver made of PEK (Polyether Ketone) polymer nanocomposite, known for not only being tough but also being light. This allows the F9 PRO’s dynamic driver to be lightly capable of producing quick, detailed and extended bass.


Drivability (Impedance):

The Fiio F9 Pro has an impedance of 28 ohm and is easy to drive. This makes it ideal for all type of portable Digital Audio Players (DAP’s). Even my Samsung Galaxy S8 could push the Fiio F9 Pro to very loud volume levels.

Albums & Tracks used for this review:

  • Martin Garix – Animal (Tidal Hi-Fi)
  • Daft Punk – Get Lucky (Flac 24bit/192kHz)
  • Lorde – Team (Flac 24bit/48kHz)
  • Michael Jackson - Billie Jean (DSF)
  • Future Heroes – Another World (Tidal Hi-fi)
  • Saskia Bruin – The Look of Love (DSF)
  • Diana Krall - So Wonderful (DSF)
  • Jeah Barbur – Seni Seviyorum (Spotify)
  • LP (Laura Pergolizzi) – Lost On You “Live at Harvard and Stone” (Tidal Hi-Fi)
  • George Micahel – Older (Tidal Hi-Fi)
  • Mile Davis – Kind of Blue Album (Tidal Hi-fi)
  • Dire Straits – Money For Nothing (DSF)
  • Emmanuel Pahud (Claude Debussy) – Syrinx (Apple Music)
  • Otto Liebert & Luna Negra – Up Close “Album” (DSF) – Binaural Recording
  • Alboran Trio – Autumn Mist (Tidal Hi-Fi)
  • GoGo Penguin – Fanfares (Tidal Hi-Fi)
  • Opeth – Damnation (Tidal Hi-Fi)
  • Megadeth – Sweating Bullets (Flac 16bit/44kHz)

Sources used for this review:

  • IEM : Fiio F9 Pro, iBasso IT01, TFZ TEQUILA1, Dunu Falcon-C
  • DAP/DAC : Cayin N5II, Chord Mojo, Hifiman HM603s, Nexum Aqua+


The Sound:

Please Note: This review is written after a bun-in process of 120 hours. I have used the stock black silicone ear tips during this review that are included to the package.

a. Tonality and Presentation:

The Fiio F9 Pro has well balanced sound signature with a mildly recessed midrange, which sounds warmer then neutral. It is a quite dynamic sounding IEM with one of best resolution levels in this price range.

b. Frequencies:

The bass of the Fiio F9 Pro sounds quite natural in its presentation with a good amount of impact and rumble when it called for.

The sub-bass area between 20 – 50 Hz is well presented and has good body and weight, but doesn’t reach to the lowest register. The overall bass speed is pretty good and the sub-bass presentation in Martin Garrix – Animal sounds pretty fast and controlled, which makes it suitable for genres like electronic, rap etc. but not on a bass-head level.

Bass notes have more presence than sub-bass notes and this tuning gives the Fiio F9 Pro some nice dynamics without to make the sound too boomy in this frequency region. The transition between bass and midrange is also pretty well done, which is avoiding any muffled and veiled presentation of instrument and vocals.

The Fiio F9 Pro has a quite balanced (maybe mildly v shaped) sound signature as I mentioned before, where the midrange is slightly recessed. There is a good amount of air, where instruments have a nice sense of space without to sound too distance. This tuning allows Instruments to sound quite natural and gives it a clean and detailed presentation. The midrange of the Fiio F9 Pro has also some good texture and definition with some nice a level op transparency.

Both male and female vocals sounding quite natural and have a nice emotional presentation. But female vocals like Saskia Bruin, Jehan Barbur. etc. sounded in general a tad more delicious.

The upper midrange of the Fiio F9 is nicely presented, which sounded quite controlled in almost any track I have listened. I have heard only some stress, which was only noticeable in some instrument intensive passages with instruments like violin, cymbals, etc.

The treble range of the Fiio F9 Pro sounds a bit hot, but has a good level of clarity and detail retrieval. Also the treble speed and extension of the Fiio F9 Pro does a good job in some complex tracks like GoGo Penguin’s – Muration. The treble range of the Fiio F9 Pro is providing the overall sound a spacious presentation, which is a big welcome in this price range.

The treble range of the Fiio F9 Pro sounds quite detailed and has a nice level of resolution. The upper treble range doesn’t sound too bright and there is also no unnecessary boast that could cause otherwise to harshness and sibilance.

c. Soundstage and Imaging:

The Fiio F9 Pro is an airy sounding IEM with a relative wide soundstage. The stage has a good wideness but is missing of some depth. The overall performance for imaging and instrument placement is pretty good and is represented in a quite natural way.



Vs. Dunu Falcon-C:
The Dunu Flacon-C sounds more aggressively V shaped compared to Fiio F9 Pro, which has a more balanced tuning.

The Dunu Falcon-C has more mid-bass impact than Fiio F9 Pro, which sounds more balanced at the bass department. The overall speed and extension of the bass is nearly identical, but the Dunu Falcon-C’s bass performance is very fit depending and can vary from people to people. With a deeper insertion and the right ear tips, you can archive some nice rumble. The bass of the Fiio F9 Pro is tighter and has additional control.

The midrange of the Dunu Falcon-C sounds a bit thinner and more distant, but has good transparency and definition. The Fiio F9 Pro sounds slightly warmer and fuller at the midrange, which makes its vocal presentation more intimate. Dunu Falcon-C sounds a bit more airy than Fiio F9 Pro.

The Fiio F9 Pro has additional transparency and clarity in its midrange, but the overall resolution of the Flacon-C is nearly the same. The Dunu Falcon-C is missing some micro detail, due the more distant instrument presentation.

The upper midrange of Fiio F9 Pro sounds slightly more detailed and more controlled then those of the Dunu Falcon-C, which has otherwise a great performance.

The vocal performance of the Dunu Falcon-C is pretty good with male vocals, but some female voices like Laura Pergolizzi sounding a bit thin too for my taste where the Fiio F9 Pro performs more organic with its presentation. The Fiio F9 Pro has also a fuller and more emotional vocal presentation.

The treble range of the Dunu Falcon-C sounds detailed and airy same as the Fiio F9 Pro. The Dunu Flacon-C has the upper hand for treble extension, while the F9 Pro sounds smoother and has better control, especially in the upper treble range where the Falcon-C has some problems with instrument like cymbals and violins. The Fiio F9 Pro sounds also a bit hot compared to the Dunu Falcon-C.

The Dunu Falcon-C has a very expansive soundstage which is wider and deeper than those of the Fiio F9 Pro. But the problem is that this presentation sounds a bit unnatural especially with live recordings like acoustic, jazz, blues etc. genres, where the F9 Pro has a more organic and natural presentation.


Vs. iBasso IT01:

The Fiio F9 Pro and the iBasso IT01 are pretty good in the bass department. But there is some difference; the Fiio F9 Pro sounds more energetic, while the iBasso IT01 has a more dynamic bass presentation. The iBasso IT01 is a bit faster and has, while the F9 Pro has the upper hand for control. The bass texture on both devices is good but the IT01 has slightly more bass body. Both IEM’s sharing nearly the same level of bass resolution and there is no clear winner.

The Fiio F9 Pro sounds bit warmer than iBasso IT01, with the same V shaped tuning, which results to a distant midrange presentation. The midrange characteristic of the F9 Pro gives it additional air, while the IT01 sounds more intimate. The iBasso IT01 sounds also more transparent in the midrange department with good dynamics, while the F9 Pro has a more energetic presentation.

The vocal presentation of the IT01 tastes better with male vocals, while the Fiio F9 Pro sounded great with female vocals. The upper midrange of the IT01 has slightly more presence and sounds crisp, while the F9 Pro sounds more balanced and controlled.

Both have a well defined treble range with a nice amount of sparkle. The treble range of the Fiio F9 Pro sounds a bit hot, compared to the IT01 which feels more vivid and energetic. The iBasso IT01 has a good amount of detail retrieval, which can be compared with those of the F9 Pro.

When it comes to the soundstage both are performing well. But there is a difference in orientation; the IT01 has the wider soundstage, while the Fiio F9 Pro has more depth in presentation.


Both the TFZ Tequila1 and the Fiio F9 Pro have a V-shaped sound signature, while the F9 Pro has more balanced tuning.

The TFZ Tequila1 has more sub-bass impact which reaches also to a lower register, while the F9 pro sound more controlled in this department. The Fiio F9 Pro has the upper hand for bass quality and speed, which sounds more mature and with additional extension, compared to the energetic presentation of the Tequila1. The Fiio F9 Pro has also the smoother bass texture then Tequila1.

The midrange of the TFZ Tequila1 sounds crisp and nice textured, while the Fiio F9 Pro sounds more natural and engaging. The detail level is of the Fiio F9 Pro is slightly higher, which has also additional transparency. The vocal presentation of the TFZ Tequila1 is a bit more forward especially with female vocals, while the Fiio F9 Pro sounds more distant and natural.

The upper midrange of the TFZ Tequila1 is more prominent then those of the F9 Pro which gives the sound a vivid presentation. But the Tequila1 has some control issues with instruments like violins, pianos etc. where the Fiio F9 Pro does a better job.

The treble range of the TFZ Tequila1 is brighter, than those of the F9 Pro. The Fiio F9 sound more balanced and has the more controlled presentation. After all, the TFZ Tequila1 performs very well for a dynamic driver IEM and the treble speed of both IEM’s is nearly identical and there is no clearly winner. Both the TFZ Tequila1 and the Fiio F9 Pro have a nicely textured top end, with good clarity.

The upper treble range of the TFZ Tequila1 sounds a bit aggressive compared to the softer presentation of the F9 Pro, but there is no unnecessary harshness. The upper treble extension of the TFZ Tequial1 is better, while the F9 Pro has the better resolution.

The difference for soundstage performance is very low, but the Fiio F9 Pro has the overall wider and deeper soundstage presentation. The placement and imaging of instruments and vocals is slightly better with the Fiio F9 Pro.


Fiio did a great job by making such a good product for an affordable price. The Fiio F9 Pro sounds great out of the box with its quite detailed and balanced sound signature, has great ergonomic and a stylish appearance packed in a box with lots of accessories. Well done!

Summary (plus and minus):

  • + Nice balanced sound signature
  • + Good amount of detail
  • + Great build quality and ergonomics
  • + Lots of accessories (2 x cable, 2x case, etc.)
  • - The treble sounds a bit hot

This review was originally posted on "Moonstar Reviews" :
Pros: Excellent Sonic Quality, Amazing Fit and Comfort, Excellent Ergonomics, Clear, Vivid, Energetic, Balanced, Clean Sound, Good Instrument Separation, Large number of accessories included with them, Great Overall Build Quality, Really nice price tag
Cons: At this price, there is no con to them
FiiO F9 Pro - Harder, Better, Faster, FiiO

FiiO made an updated version of their well-received FiiO F9 IEMs, this time using High-Quality Knowles BA drivers, giving the entire sound a new definition. The Bass driver is the same, but with better BA drivers taking care of the midrange and of the treble, F9Pro is surely to sound different from F9.


We reviewed FiiO F9 a while ago, and it was quite an intriguing little IEM, with only one rather large downside, which we named back then, the existence of its bigger brother, FiiO F9Pro. It is time to see what F9Pro is all about, but first, we'd like to invite you to read more about FiiO F9, so you know what F9 evolved from:

It should be noted that we have absolutely no affiliation with FiiO, we are not receiving any incentive for this review or to sweeten things out. This review is not sponsored nor has been paid for by FiiO or anyone else. We'd like to thank FiiO for providing the sample for the review. The sample was provided along with FiiO's request for an honest and unbiased review. This review will be as objective as it is humanly possible, and it reflects our experience with FiiO F9 Pro. Every opinion expressed belongs to George and Audiophile Heaven and we stand by it, the purpose of this review is to help those interested in FiiO F9 Pro find their next music companion.

About me


First things first, let's get the packaging out of the way:

FiiO F9Pro comes in a very similar package as FiiO F9, with an amazing attention to detail, and an excellent set of accessories. The largest difference between the two is that F9Pro comes packaged with a little extra pouch that wasn't present for F9.

The same elegant box, with a high-resolution image of F9Pro printed on the outside, with a lot of technical details written on the back of the package, and with a very complex box content is present with F9Pro, as it was with F9.

The main cardboard box needs to be taken out of the beautiful box with all the nice graphics on it.

Within the main box you can find FiiO's legendary carry box, which I eventually got to store and carry my IE800 and even RE2000 in as it allows for better protection and as I can have an airtight seal with silica bags inside.

Inside FiiO's legendary box, you will find another carry pouch, in grey color, which doesn't come as a hardcore protective case for F9Pro, but more of a casual storage option that looks pretty friendly and elegant.

There is a large number of tips included with F9Pro, along with two cables, one of which is single ended, and one of which is Balanced. The cables are very good quality, and while they aren't as thick or serious looking as those found with iBasso IT-01, they surely stood my usage tests and are supler and more flexible.

There are a large number of tips included with F9Pro, out of which I found that the silicone tips with the transparent color provided the best fit and sonic performance, although the other ones were pretty good as well.

All in all, at around 150$, the package is really good and has all that is necessary and maybe even more for any user to enjoy F9Pro to the fullest.

What to look in when purchasing an entry-level IEM

Technical Specifications

Build Quality/Aesthetics/Fit/Comfort

The build quality and the comfort are pretty much the same as those found on FiiO F9, the outer shell being exactly the same. In a few words, the build quality and the comfort are both golden, F9Pro is extremely well built, with solid but not too rigid MMCX connectors, have a deeper fit with excellent isolation and they are some of the best IEMs there are in this price range.

The earing can be done only over the ear, and the cables F9Pro comes with do not permit any other wearing style.

We'd like to link the review on FiiO F9 for more information on the comfort and build quality:

Sound Quality

Here is where things depart from F9 and where they get more interesting. FiiO F9Pro sports much higher quality BA drivers for the midrange and for the treble, resulting in a more detailed sound

No burn-in is recommended by FiiO, but a little over 50 hours has been applied before taking the impressions of FiiO F9Pro.

Starting with the overall signature, the overall balance hasn't changed quite that much from FiiO F9, F9Pro is also quite V-shaped in its signature, with an enhanced bass, a slightly recessed midrange, and a fairly energetic top end, with a lot of sparkle and energy in the higher registers. It should be noted, though, that F9Pro is slightly more balanced in their sound, only if slightly, having a more natural response.

The bass is deep and goes down bellow without an issue, provides excellent impact and rumble, and has a natural decay, being revealing enough to show some of the nicer textures in the bass of certain songs. The punch and slam is fairly good, and given the fact that F9Pro is more balanced than F9, it also feels like it has more sub-bass and lower mid-bass, giving them a deeper overall tuning.

The midrange starts to be different from F9, as F9Pro has more detail and a more even upper midrange, with less of an upper midrange / lower treble spike, the spike being extended to a wider area, leading to a more coherent tuning. Vocal tonality is quite good and there's not much to complain as F9Pro does everything F9 did, but has better detail, better clarity, and feels more vivid in the long run. The body of the midrange is quite natural, and while the male vocals might be slightly behind when compared to the rest of the midrange, the body is much improved from the original.

The treble also felt considerably better extended and airier than the treble on F9, with a much more natural cymbal body and decay, sounding rather correct and tonally pleasing this time. There is a slightly aggressive detailing with F9Pro, which gives a good portion of its revealing abilities. Guitars and trumpets have a very crisp sound to them, and bells and other symbols sound enticing and dazzling. Compared to its little brother, F9Pro is easily the better performer in the treble, with a better extension, as well, a higher quantity of air in the treble, and much better micro-detailing and micro-texturization. Where F9 might have ended some upper-treble notes a tad short, F9Pro extends much better and touches the sweet spot quite well.

The overall tuning still is similar to F9, but F9Pro is like a super F9 given steroids and made clearer, more vivid, and more balanced, and with a better and more satisfying extension both to its treble and to its bass.


The soundstage of F9Pro is actually quite similar to that of F9, with a good amount of width and depth, being rather well-rounded, reaching the boundaries of one's head, sometime extending beyond as well, being quite immersive. Imaging is one step ahead of F9, especially with F9Pro's more balanced tuning, and the good clarity of F9Pro also provides an excellent layer and instrument presentation, even when compared to their own brothers.

Portable Usage

I have been using F9Pro on the streets of Bucharest and even in heated gaming sessions a few times, and the portable usage of them is quite satisfying. F9Pro does benefit quite a bit from a revealing source, on behalf of their own revealing nature, and they seem to be rather immune to hiss and other issues, being rather good at combining with almost any portable source one can think of.

There is a good amount of isolation from the outside noise, and they can safely be worn during a careless stroll through the noisy urban streets of Bucharest, as well as be worn in a noisy gaming environment. The isolation goes more or less the same as the original, and the originals were quite good in this aspect.

When it comes to long-term usage and comfort, if one can use the ear guides without any issue, F9Pro should have a golden comfort, as they have a good fit in general, they have a vent which avoids any kind of over-pressurization, and they have a good amount of tips included with them, so they should fit with most ears without much hassle.

The cables included with F9Pro are both rather supple and easy to walk and run with, both looking good to resist some rough usage, and the shells seem quite resistant to moderate usage as well. This pair doesn't have a single scratch, even after being used for a good few weeks, so F9Pro should keep up with your active lifestyle just fine.


FiiO F9Pro vs Astrotec AM850 - F9Pro tends to have a deeper fit, along with more isolation from the outside noise, but they aren't more or less comfortable, both AM850 and F9Pro being golden in their comfort. FiiO F9 Pro comes with a much larger amount of accessories that might be useful than AM850 comes with, and F9Pro also has a better carrying case solution. The fit is over-the-ear only for F9Pro, thing which should be kept in mind, and the cables on F9Pro are not as nimble as AM850, but they are detachable on F9Pro. The sound is quite similar between the two, the biggest difference being in the treble, where F9Pro is a bit peakier with a stronger treble than AM850, which is quite smooth. Extension both ways is excellent on both, and both have a vivid, vibrant, clear, clean and dynamic sound. F9Pro feels a bit like an upgrade from AM850, but it is also more expensive than AM850.

FiiO F9Pro vs Westone UM1 - FiiO F9Pro has a brighter sound that can come through as more balanced, less laid back, less dark and closer to a natural sound. The sound is more detailed and provides better vividness for F9Pro, while UM1 feels more relaxing and a considerably more laid-back presentation. The bass, on the other hand, is thicker and more satisfying on Westone UM1, being both harder with each hit, and providing a more visceral feeling through and through. The treble is smooth on UM1, but the amount, detail and air of the treble is much better on F9Pro, which also extends much higher than Westone UM1. The fit and comfort is at golden levels on both, along with their portability. The build quality seems excellent on both.

FiiO F9Pro vs Kinera H3 - The sound is more balanced on F9Pro, with a much more coherent signature, much better body for both the midrange and the treble, less sibilance, and better / deeper bass presence, although the bass of H3 is also quite amazing on its own. F9Pro has a wider soundstage, while H3 has a slightly deeper soundstage. The comfort is better with F9Pro, as H3 had driver flex and is larger in the Shell Size. H3 is very well built, and it has a hard carrying case, which might come in handy, but F9Pro sports an even better carrying case, and a similar construction quality. F9Pro is more expensive than H3 though, and H3 has a more aggressive detail revealing presentation ability, being the more detailed IEM.

FiiO F9Pro vs iBasso IT01 - iBasso IT01 probably F9Pro's largest competitor, as it is considerably less expensive, but comes with a set of really interesting abilities. Starting with the bottom end, IT-01 has a similar amount of sub-bass, but much more mid-bass, even after proper burn-in. This results in a rather different presentation, where F9Pro comes with a punchier bass, with more tactile feeling, but IT-01 is the more visceral and more obliterating presence in bass. The midrange is similar between the two, even the detail levels being similar, but IT-01 feels more dynamic where F9Pro feels more energetic and vivid rather than dynamic. The treble is an interesting area, as F9Pro and IT-01 both have a nice extension in their treble, and both are V-shaped in their signature. The price is considerably lower with IT-01 and the construction quality is similar, but IT-01 has a cable that looks more serious than F9Pro. IT-01 does not come with a balanced cable in its package though, but it has an amazingly good carrying case. Chosing between the two is very hard, as both have amazing things going on for them, but IT-01 is the more dynamic performer, where F9Pro is more vivid, and IT-01 will have a thicker presentation with more body, where F9Pro will feel less warm and more neutral in comparison.

Recommended Pairings

FiiO F9Pro + HIFIMAN MEGAMINI - Megamini proves itself as an excellent driving force for FiiO F9Pro, as it handles them quite well, giving them large amounts of energy and vividness for their sound, with a rather wide soundstage and a good amount of details.

FiiO F9Pro + Cayin N5ii - Cayin N5ii is yet another amazing DAP to combine with F9Pro as it provides them with an excellent amount of details, and a very natural and reference presentation, a good amount of detail and clarity, and an excellent overall tonality. The abilities N5ii has with F9Pro are endless, and the setup is quite nice, and it should be noted that N5ii's balanced output works quite well with F9Pro.

FiiO F9Pro + Opus #1s - #1s is to easily give F9Pro a very powerful presentation, with more strength to each note, and maybe a tad more body to their sound, giving them an ever so slightly warmer presentation that can feel quite satisfying.

FiiO F9Pro + X7mkii (AMP5) - FiiO IEMs always sound amazing with FiiO DAPs, and X7mkii is an excellent DAP to prove this. The sound stays well within the territory of neutral, with a neutral and clean signature, an excellent detail retrieval ability , and an amazingly high amount of energy and vividness. There's no downside to this combo, and the overall excellent ability of X7mkii (streaming, 2 microSD cards, clean sound), along with F9Pro's comfort and nimble nature makes this combo a very desirable setup.

Value and Conclusion

First, it is important to consider that we're talking about a 150$ IEM, and that this is a bit higher than the original, but still places F9Pro in the entry-level, inexpensive IEM area. Even so, the amount of accessories that come with F9Pro, from the large number of tips included in the package, all the way to the two excellent cables you can find with it, are worthy of a higher price range, or rather, until very recently could only been found on very expensive IEMs and headphones.

There's no mistaking here, F9Pro is much better than the original, it is much more linear and much more balanced in its signature, and virtually everyone out there will surely agree with this statement, making F9 a bit obsolete, unless one is quite constrained by this budget. This doesn't make F9 an less good, but it makes F9Pro that much better, being like a very well re-imagined version of the original.

Outside it is the same IEM, but inside, FiiO made just the right changes to hit a sweet spot with F9Pro, this one being one of our favorite IEMs in this price area, and it'll probably stay a favorite for a while, having very few competitors that offer a similar overall performance, iBassi IT-01 being one that we should name.

All in all, FiiO F9Pro is one of the best IEMs there are for 150$, especially if you liked the original (F9), and if you are looking for something even more dynamic, more balanced, and very natural in its sound. The extension is amazingly good both ways, having a deep bass, a vivid midrange and a sparkly treble that is sure to impress any listener, bringing a lot of emotion to music and a tear to our eyes when we listened to an impressive violin work through them. If you have 150$ and you want one of the best IEMs there are for this price, make sure to check out FiiO F9Pro as they are surely not only as impressive as F9, but much more, being better in every direction imaginable.

Stay safe and remember to always have fun while listening to music!


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Pros: Price, dynamics, bass impact, form factor, cable
Cons: Hot treble can be a dealbreaker
DISCLAIMER: This was a review tour unit provided by Fiio.

Fiio has become an interesting beast in the headphone community, chiefly for their ability to pack a lot of fairly high-quality features into low-cost products. They've been tearing things up with their various portable amps and DAPs, so when they decided to dip their toes into the IEM world with the F9 and F9 Pro, I was excited to hear what they'd come up with.

The end result? Good, but not great.

I'm going to be stacking these alongside the KZ ZS6, 1More Quad, Mee Pinnacle P1, and iBasso IT03, and I realize the F9 Pro is lower in cost than three of the four (and nearly half the price of the IT03), Fiio is usually known for punching above their price class so I don't think this is terribly unfair. Plus, that's what I have lying around for points of comparison.

The presentation is solid. A simple small box, the units held in foam with a little carrying case holding the cable and a handful of plastic baggies with an array of tips. I really like this, truth be told. I find some brands go way overboard with these huge boxes and all this needlessly fancy appearance. I'm buying headphones, I'm not buying a box. Keep it classy, keep it simple.

The F9 Pro looks very sharp. Plastic housing is a bit underwhelming, but I'm a big fan of the ripple appearance. They just look cool, for lack of a better word. There are tips of varying kinds, Fiio has the silicones broken down into "balanced," "bass," and "vocals," along with a bunch of foams, all of varying sizes. This is pretty awesome, normally you get generic tips and foams, this is really nice on Fiio's part.

As a side note, the F9 cable is my favorite IEM cable ever. No microphonics, the phone controls are well placed and designed, and man I love how they hang over the ear. No memory wire, but it sits perfectly.

Okay, time for the sound. All the above is great and all, but what matters is what happens when they're stuck in your ears. I'm a big fan of hybrids, they tend to have a different character of sound compared to a single DD or all BA array. So I threw on the balanced mediums and turned on some music. The fit, by the way, was perfect for me. Deep insertion, comfy as anything. I have pretty roomy ears, though, so it's rare for an IEM to give me fit issues.

Whew lads, that treble.

I should note that my listening habits trend toward more aggressive music (a lot of metal and hip-hop), which means the volume is a touch higher than many others will use. Certainly not blisteringly loud, but boosted up a bit. With that said, the treble on the F9 Pro with the balanced silicones was unbelievably zingy, sibilant as anything I'd heard in a long time. It reminded me quite a bit of the KZ ZS6 in that regard. Hi hats sounded like they were inches from my ears while the rest of the band was a normal distance away.

Trying to be charitable, I gave myself an entire day of listening to various music with these, trying to let my ears adjust. It was actually a serious disappointment because under the treble I could tell there was some good stuff going on. Impact of the bass was good, soundstage had that right balance between being spacious and staying tight, but wow that treble.

Finally, I threw some comply foams on there and oh hey how about that, now they're listenable. I had come dangerously close to just sending them to the next person on the tour after the first two days, but with a set of foams, the treble is tamed, and now I can really evaluate the sound.

The bass is good. Like, really good. It's not huge, but it has that powerful impact that makes the rhythm section in music sound visceral. This is a big reason I like DDs in hybrid setups on IEMs. As good as a BA can be, there's just an intangible quality that a good dynamic gives that I prefer. The bass sounds smooth, extending way down into the sub-bass territory with no struggle. I threw on a few hip-hop tracks that I know dip below 30Hz and I was impressed that there didn't appear to be any severe drop off. Yes, there's a small bump in the midbass, but that's to be expected and usually preferred because that's where all the impact is.

Mids are a bit hard for me to evaluate here largely because of the treble. Vocals of all kinds are fairly smooth, I got no problems here. The frequency response shows a slight dip in the mids, but it's certainly not severe. The vocals never sound buried, and female vocals in particular have the right amount of meat to them that keeps them from sounding overly thin and weak. I actually think if you're listening to mid-centric vocal music, these will really work for you.

And then there's the treble. Yes, the foams tamed the treble quite a bit, but even then it was a problem. I readily concede that part of this is in my choice of music. Metal tends to have a lot happening with the drum kit, and the cymbals are going to be doing a lot. When I swapped genres to more "gentle" music and pulled the volume back, it became less of an issue. A bit of hiss, but nothing unpleasant.

Soundstage and imaging are good. The music doesn't sound like it's cramped into your head nor do you feel like you're in a cavern. I'm not the world's best judge of soundstage so that one I'll leave to people better suited to evaluate it.

I dislike trying to break the sound down into components, so let's take a moment to talk about overall coherency because this is a spot where the F9P really shines. Despite the hot treble, the F9P's total is greater than the sum of its parts, and even when I found myself grumbling at harsh cymbals, I didn't want to pull them out of my ears (again, using the foams as opposed to silicones), because the dynamics of the F9P are just so damn good. The F9P has an energy to it, the music moves as opposed to resting back. The bass's fullness without sounding bloated meant rhythm sections had weight to them.

Onto some comparisons:

KZ ZS6: This turned out to be a better head-to-head than I expected because both of them have that hot treble in a hybrid setup, but unsurprisingly the F9P is better top to bottom. The sound is more coherent, more full, not as severely V-shaped, plus far more comfortable. I'm more charitable with the ZS6's sibilant treble because they're about $30 as opposed to $130, but obviously the ZS6 is inferior. Was fun to compare, but aside from that treble giving me fits there wasn't anything to say.

Mee P1: This is an interesting comparison because it's a single dynamic versus a hybrid. The first thing to notice is that the P1's emphasis moves more towards the mids than the treble. The bass is less impactful and they just sound more "neutral" as opposed to "big" overall. The F9P wins on the "fun" front, but the P1 wins in having no big imbalances. This isn't terribly surprising, sometimes being competent across the boards is also boring. This was the one I had to struggle with the most because after getting fatigued from the F9P's treble issues I'd go to the P1, but then I'd miss the F9P's energy.

1More Quad: Here's a contrast. I've discovered that people's opinions of the Quads are really varied. Some call them unbearably bassy, others say the bass is lacking. To my ears, the Quads have one hell of a midbass hump that seems to vary between really working in the music and really not. The treble on the Quad is less up front, however, the F9P's treble is smooth. So even though the Quad isn't as sibilant, its treble sounds more brittle in comparison. Oddly enough, the Quad is what I found myself the least inclined to swap to in this head to head.

iBasso IT03: This one almost doesn't feel fair because the IT03 is my favorite IEM of the moment and it's twice as expensive as the F9P. It's a beast. A sub-bass tilt gives the IT03 a reach that none of the others here have, and the sound is just powerful overall. It does have a minor treble lift alongside the F9P, but it's more subdued and less troublesome. If anything, the IT03 can be too bassy by comparison, but I found this to be no issue. There's little to say here, as I did these comparisons, the IT03 was the one I wanted to listen to most.

In conclusion...

The F9P definitely works better with the volume kept more conservative, and I can see how other reviewers praise it for being clear and detailed into those applications. Reviewing headphones is as much about evaluating them in the "generic" case but also in a given use case. For someone who listens to relaxed music at low volumes, the F9P is going to tick a whole lot of boxes really well. Spotify has a "Songs to Test Headphones With" playlist and listening through that with the F9P and foams in at a fairly low volume truly was a great experience. The silicones were still a no-go.

HOWEVER, when I review headphones, I review them in "real world" scenarios, because I feel that's the only way to get an honest appraisal. I review them by listening to headphones how I listen to headphones day in and day out, because otherwise what's the point? If I have a great experience listening to music I never listen to at low volumes, that's not helping me when I fire up my favorite albums.

So the end result is a headphone that I find it difficult to affix a number to, because on one hand there's how well they fit me personally, and on the other there's how I could see them fitting others. For me personally, they're above average, but the treble spike keeps me from being able to listen to them for long periods. When I try out other music, their strengths become far more apparent. In a way, it bums me out, because when I do listen to music that works with them, it really works, but then I go back to my chosen genres and that hot treble comes flying out again.

I suppose the summary then is that the F9P is a very competent, well-made headphone with a lot of stuff going for it, but like some full size headphones with a similar issue (Senn HD700, Beyer DT990), it has that treble that, depending on what you listen to and how you listen to it, may or may not spoil the whole experience. If that's not something you think will be an issue, then there is absolutely no reason not to get the F9P.

Sources: Dell Inspiron Laptop (with and without Audioquest Dragonfly Red), LG v30, desktop rig with Questyle CMA400i.
Best review title ever! I’m curious - did you attempt eq on these?
Pros: comfort, bass decay, braided cable, build quality, scalability
Cons: some heat in the sibilance region, but not fatiguing (weird ....I know).

I am a grateful participant in the Fiio F9 Pro review tour. So thank you Fiio for providing this opportunity to us head-fiers. Your engagement with the community is outstanding! The review unit was not a “keeper” but had to be shipped on to the next reviewer. I am, however, eligible for a discount on my next Fiio purchase because I pledged to write a review. Fiio insists on honesty, and that’s what you and they will encounter with the below.

I hate to even have to say it, but sound impressions are subjective - and so this review will undoubtedly be subjective. Not only that, but sound can objectively change with things like insertion depth, tip choice, etc. Here’s my usual rant: high frequencies in a small space (and low frequencies in a larger space) will create standing waves. It’s physics and you can’t avoid it. These frequency dips and spikes will present differently based on the volume of air in your ear canal. For this reason, I’m a fan of foam tips as they help decrease these reflections. While the treble is decreased, it is usually more linear with foams. As with all IEMs, I have used genuine comply foam tips (large) for this review.

Also, I’ve exercised great restraint by not subjecting myself to other reviews of this particular model. I have read reviews of the original F9, but not the Pro. Once this is finalized and posted, I’ll have a look at what others thought.

Summary of the Soundscape:

The F9PRO is mildly V shaped: it has good sub bass, is hot in the bass, a tad light in the lower presence, good upper presence region, a tad hot in the sibilance region, with enough in the brilliance region to sound detailed. How’s that for a one line summary?

The pro is what I’d consider a safe sound - it strikes a good balance between consumer and audiophile. There’s enough impact to engage the listener, with enough finess and detail to satiate the audiophile. Detail is respectable and I’m hearing things that I’d not heard on my beloved Zero Audio carbo tenore. I think the BA upgrade has something to do with it. No, they can’t match my JH iems, but with a little more in the top octave, they’d put up a tough fight.

Imaging is excellent, being able to place instruments in the field with accuracy. I’m not getting the three blob separation that is common on many IEMs. The entire field from left to right is filled without gaps yet retains a clear and focused “phantom center”. Tracking instruments that pan from left to right is effortless. High marks for imaging!

I’m not the best judge on soundstage because I don’t really value this attribute in a set of headphones or ‘in ears’ as much as others. I think I’m outside the norm because I actually like the “in head” experience. With that said, there’s still enough width to sound spacious. Nothing jumped out as being out of line with other IEMs, nor was it overly congested. They didn’t sound blown out large/wide, and they didn’t sound one-dimensional in my head.

Setting Up for a Listen:

Unless otherwise noted, I used the AudioQuest Dragonfly Red, fed by an iPod Touch, playing Hifi tidal, and finished with comply foams when I took the notes on treble, mids, and bass. I listen to progressive rock and metal, so there is plenty of “busyness” and lot’s of instrumentation (mostly with vocals) to challenge this IEM.

Normally, I have to endure the torture of sibilance when I use silicone, but these took to the silicone better than other IEMs I’ve used. What I didn’t expect was how well these performed with spinfits and spiral dots. Spins sounded very much like the stock Fiio tips, and the dots sounded a bit more present. Still, I only used the silicone long enough to observe this, then promptly moved to my beloved foams for the fairest impressions (after all, it’s what I’m used to).

I also tend to obsess on treble, not that I’m a “treble head”, rather I’m sensitive to it and gravitate more toward realistic and smooth treble vs impressive or overly sparkly treble. This leads me to be somewhat overly critical of treble, so please keep this in mind as you read the rest of the review. And how fitting that we start with the….


Treble is rather pleasant overall. There’s no obtrusive spike that detracts from the music or that focuses excessive attention to it - something I was expecting given the graph of the F9 original version. I do sense a rise nearing 10k however, then the energy falls off quickly afterward; at least it seems that way in comparison to the 10khz region, so some “air” is perceivably missing. Top octave is attenuated by a few db, so the extension is not great. If there was just a few more db between 10 and 15K the treble would be more lauding on my end.

Yet the timbre is rather good. Nothing sounded fake, metallic, or shrill. It was mildly sibilant with some vocals on a few tracks that presumably weren’t mastered well, showing clearly that the engineer opted not to use a de-esser or limiter. I was fearful that consonant S and T sounds would have a consistent “wince factor” to them, based on the original F9 reviews, but I’m not hearing that much at all on the pro version. Sibilance only creeped in once in a while. Keep in mind I’m very critical when it comes to treble (very sensitive to sibilance), and still, I find the treble pleasant.

The 5-7khz region is petty well behaved with only a few areas of heat. This heat gives cymbals more of a fundamental tone (the stick strike is emphasized) vs hearing their overtones shimmering. But it is only a minor lift in this region so it’s not an issue unless you’re listening to music with never ending cymbal crashes, which tend to sit above the mids a bit. At times, the cymbals sound more “cush” than “psst”. Sound that out, and you’ll know what I mean.

The decay here is good. Cymbals don’t ring out to infinity, but the decay is convincing.


There is a perceived gap in the low mids - 500 to 1,000hz? Had this been raised, I don’t think there’d be the V shape I attributed to them in my summary. But this slight gap also provides a good deal of separation between the bass and mids, so there isn’t any bloat or intrusion into the very musical presence region.

The mids and high mids are voiced very nicely - but sit behind the bass and treble slightly. The tuning here is very good.


Bass is surprisingly deep and only slightly emphasized at 90-180 hz, making for a nice impacting sound.

Bass hits hard. Really, I wasn’t expecting this quantity. Its impact had proper punch without being anywhere near obnoxious and the decay was better than good. Bass didn’t hang around and moved in an out of the scape like a proper dynamic should. It’s not dry and instantaneous like some BAs present so I wouldn’t call it fast bass - but still nimble and authoritative. Being used to BAs, it made me realize I was missing something - something visceral - and the fiio provided that.

Source Matching:

You can tell that Fiio intended this IEM to be paired with their DAPs. On the X5iii some of the low mids were put back in place, improving the coherence and balancing out the overall sound compared to the Dragonfly Red. The synergy with the X5iii is on point. Overall accuracy of timber jumped up a notch compared to the Dragonfly Red.

Moving to my main setup, arcam rhead with iFi micro iDAC2 (my most resolving setup) - The F9 Pro scaled well with better gear revealing a tad more detail and control over the bass. Not that it was flabby to begin with, but what was very slightly rounded bass, now seems a bit more linear. Sub bass and bass became more aligned. They took the juice here admirably - and needed a bit more out of the rhead than I was expecting. I didn’t do any volume matching but can safely say these are not “super easy” to drive and will be served best by a proper amp.

Items to Note:

All of the review notes above were done using large comply foam, with a medium to deep insertion - what I’d consider standard fit. I later found that by using large foam with a shallow insertion was best sound quality for me. Any sibilance was removed, and the top octave appeared to come out some more. Did the heat at 5-7K disappear? No, but it was attenuated in relation to other frequencies. However, for my ears, I just can’t keep them at a shallow depth and move about, lest they break seal. Your ears may be different and you may find the F9P to present as I just described with other tips and methods that work for you.

Phase alignment is good - bass and both BAs working nicely together.

The rigid case stood out as a nice bonus - heavy plastic that is just the right size and incredibly functional.

mmcx connectors are not easy to detach and don’t allow effortless swivel - a good thing! very secure.

Using none other than fiio’s own 2.5mm balanced to 3.5 mm SE adapter cable, my braided cable impressions are that it is better. It seemed to carry the signal with less graininess. This can’t be measured on a FR graph, but that’s what I’m hearing. Anyway, it’s less unruly, looks nicer, feels nicer, tangles less, doesn’t have the mic inline, so it gets my recommendation.

Comfort was outstanding. Although I’d want to see a shirt clip provided (if one isn’t already). None came with my review sample.

The metal housing should provide better than average, if not really good, durability.

Bottom Line

These weren’t the best IEMs I’ve heard. But OTOH, had no fatal flaws. Finally….. they are worth every dollar of their asking price, and then some. To prove it, PM me a few weeks after this post and I’ll show you my receipt, because I will be buying them to add to my small collection.

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Pros: price, build, fit, presentation, accessories, good sound articulation and clarity
Cons: foam tip sizing, treble peak causing some sibilance
Fiio F9 Pro is a dual BA, single dynamic, hybrid in-ear monitor with detachable cabling. It comes with two cables utilizing MMCX connectors, a 3.5mm cable with a microphone, and a 2.5mm balanced cable. Also comes with 4 different types of tips, foam, large bore diameter silicone, smaller bore diameter silicones. I find that the small diameter bore silicone tips drops mids and the highs, but does it in a veil sounding way which I wasn't so fond of. I was a bit bummed that all the foam tips were on the small size, and there wasn't one that would seal my ears. I know it's ok for foam to generally be on the larger size because you can compress it to fit your ear. Fortunately, large size, large diameter bore silicone tips fit my ear very well, and I found it to be the best sounding tips.

I've unboxed Fiio products in the past, and they generally don't skimp on the packaging or accessories. The inclusion of balanced cable is a nice touch among all the accessories provide.

The form-factor pretty much nails the ergonomics I look for. It's compact, and shaped to adhere to your ear shape with the cable going over the ears.

Source pairings:

Mojo: The upper mids is emphasized a bit too much. Upper bass is a bit lacking. Bass doesn't sound even, more sub-bass presence and with the treble sounds overly U shaped. Poor match.

Opus #2: Much better match than the Mojo. Signature is more balanced than the Mojo. Also there is more bass presence. Lower treble is still emphasized, but not as much as the Mojo.

AK240: I think AK240 is the best match for the F9 Pro. I think in general AK240 has most mid presence out of the 3 players I've tried(which was needed), and sounds good out of it. Also the 240 outputs the most articulate bass of the 3. Opus #2 in comparison, quality of bass isn't up the level of the AK240(and this is generally true of all the iems I've tried).

On tracks with a bit of sibilant vocals, the sibilance is a bit over-emphasized. In general, the treble presence region has a bit of emphasis.

If the sibilance can be suppressed, I think this iem would sound better than it does. I think the boost in this treble region cause tonality to sound toward metallic for certain tracks that have good amount of that frequency band presence. Reminds me of HD800 tuning except F9 Pro has sufficient bass in comparison. There isn't a lot of bass presence, but it's quite sufficient and sound like it does reach deep to the sub-region for tracks that outputs it. The bass sounds good in articulation without bloat(this is particularly the case out of AK240 out of all the three players), but not significant in quantity(it's the level of bass you find in neutral tunings).

Playing around with EQ on the Opus #2, I discovered drop in 8khz reduces the sibilance a bit. The EQ on the #2 is a graphic equalizer, only 8khz was one of the limited options. So the treble peak is somewhere in that region. If you can EQ down the treble peak, I think the iem would sound neutral with a reference like signature.

Due to it's tuning, the general sound signature is toward clarity. With the presence region emphasis, and mids to bass sounding neutral, it outputs much articulation without warmth emphasis.

Overall a nicely built iem with good number of accessories. It's an iem to consider in the price range. Considering the price, it's a good value for what you are getting.
Pros: •value
•balanced tonality
•great technical performance for the price
•really well-done blend of dynamic bass character and control
•plenty great included accessories
•build quality, ergonomics, design
Cons: •treble somewhat on the hotter side
•a bit more treble linearity would be desirable
•mids probably a touch too much on the leaner side

Originally posted in English on my mixed language English and German audio review website, the "Kopfhörer-Lounge", here comes my review of the FiiO F9 Pro hybrid triple-driver.


FiiO have definitely come a long way since they started – and they turned into a large, influential and important audio company over the years.
I have owned (and still do) several of FiiO’s products, and was among the first who purchased the first generation of the X3 digital audio player that, while it experienced some delays until it finally hit the market, probably introduced a new era of portable audio players, bringing a solid noise performance, low output impedance and good measurements down to a reasonable price.

As time went by, FiiO’s line of digital audio players evolved more and more, and they eventually also introduced various in-ears, such as the hybrid triple-driver F9 that now gets a “Pro” version which basically differs from the regular one by using two different Balanced Armature drivers from the well-known manufacturer Knowles.

How does it sound? Let’s find it out!

Full disclosure: I was provided with a sample of the FiiO F9 Pro in-ears free of charge for the purpose of an, as always, unpaid, honest and unbiased review that reflects nothing but my own impressions and wasn’t given any directions/guidelines, no matter how it would turn out.

Technical Specifications:

MSRP before Taxes: $139.99
Type: Hybrid In-Ear
Drivers per Side: 3 (1x dynamic driver, 2x Balanced Armature (Knowles TWFK-30017-000))
Frequency Response: 15 Hz – 40 kHz
Impedance: 28 Ohms
Sensitivity: 106 dB/mW
Maximum Input Power: 100 mW

About hybrid In-Ears:

As you can already see from the technical specifications and introduction, the FiiO F9 Pro is a little different from most In-Ears produced in the past decade and doesn’t only rely on dynamic or Balanced Armature transducers for sound reproduction, but combines both in one shell.

Most In-Ears use dynamic transducers for audio playback which have the advantage of covering the whole audible spectrum and achieving a strong bass emphasis without much effort. Valuable dynamic drivers are often said to have a more bodied and musical bass that has a more soft impact and decay and lacks of the analytical character that BA transducers are known for. On the downside, in contrast to headphones with other driver principles, dynamic transducers often have a lower resolution.

Higher-priced and especially professional IEMs mostly use Balanced Armature transducers, which usually have got a higher resolution than dynamic drivers, are faster, more precise and have got the better high-level stability, which is important for stage musicians that often require higher than average listening levels. On the downside, it is usually somewhat difficult (although not impossible) to cover the whole audible spectrum with just one single BA transducer, and a strongly emphasised bass is often only possible with multiple or big drivers. Some people also find In-Ears with BA transducers to sound too analytical, clinical or cold (in several active years in a German audio community where I wrote multiple reviews, gave dozens of purchase advice and help, from time to time I heard people that got into BA earphones for the first time using these attributes for describing BA earphones, especially their lower frequencies).

Hybrid IEMs unite the positive aspects of both driver principles and use one dynamic transducer for the lows reproduction and at least one BA driver for covering the midrange and highs, wherefore the often as “musical” described bass character remains and the BA transducers add resolution, speed and precision to the mids and highs (, at least in theory) – and that’s what the FiiO F9 Pro does with its technology. It is addressed to those people who perceive the clinically-fast character of BA transducers as unnatural and prefer body and weight, but want to keep the mids’ and highs’ resolution, nimbleness and precision.

Delivery Content:

One word: Plenty.

You don’t only get the in-ears, but also two pairs of cables (single-ended 3.5 mm with in-line three-button remote control and microphone, 2.5 mm TRRS), two storage cases, and last but not least four different sets of differently sized ear tips (3x silicone, 1x foam).

Looks, Feels, Build Quality:

The FiiO F9 Pro features a similar shell design as the normal F9, however its colour is different and it has got “Pro” markings on the inner half.
Build quality is good and the metal shells appear valuable and sturdy.

The two carrying cases are nice as well and have got soft padding on the inside to protect the ear pieces from scratches. The smaller of the two is, in my opinion, nice if you want to carry around some ear tips or a spare cable, and you can store the accessories in it and then put it inside the bigger hard-case together with the in-ear. Or, if you prefer to carry a smaller bag with you, the smaller of the two cases also offers already enough room for the F9 Pro.

If you are familiar with DUNU’s more recent in-ears, you will probably immediately recognise the F9 Pro’s standard remote/mic cable, as despite lacking braiding/twisting compared to the other included cable with 2.5 mm TRRS plug, it is very soft and super flexible, and therefore among the best, if not the best, non-twisted cables on the market.
Apart from directly above the y-splitter that reads “Pro”, there is good strain relief, but unfortunately no chin-slider.
The ear guides are pre-shaped, flexible silicone tubes without any memory wire. They automatically adjust to the ears’ radius.

The MMCX plugs sit firmly and tight in the sockets, and what I find nice are the matching coloured side-markers on the cable and the in-ears themselves.

Oh, and before I forget to mention it: the remote control is really nice since the volume buttons are easy to distinguish and since it doesn’t require much force to push them, yet definition is good and not too soft.

Comfort, Isolation:

Thanks to the general shell design that was made popular by Shure and Westone, the F9 Pro sits ergonomically in one’s ears and most people should be able to wear it for hours without experiencing any discomfort.

Thanks to the nice cable, microphonics are close to being inexistent.

Noise isolation is on the lower to average side, which was to be expected given the F9 Pro is vented.


For listening, I mainly used the iBasso DX200 (AMP1 and AMP2 module) and Cowon Plenue 2. The FiiO was always used with the included single-ended cable during comparisons and listening.

Mainly the largest included white silicone tips were used for listening and all comparisons.

Frequency response measurements can be found here:


Quite interestingly, the included white silicone tips have got the least amount of upper treble elevation out of all included silicone tips. They also slightly lift the lower and middle treble (~ 3 to 6 kHz) though.
Covering the dynamic driver’s front cavity vent, which is true for pretty much all dynamic driver and hybrid in-ears, will increase bass quantity quite noticeably. Depending on your individual ear anatomy, this vent might be either free or fully blocked.
Interestingly enough, in my ears, this vent remains quite free, which is rather rarely the case for my ear anatomy, so all of the following impressions are written with the front cavity vent remaining free.
Depending on individual ear anatomy, bass levels can also be anywhere in-between.

Bass is on the balanced side, with a rather modest lift of ca. 5 to 6 dB compared to an in-ear that is diffuse-field flat in the lows, such as the Etymotic ER4SR. It starts rising around 800 Hz and reaches its climax around 200 Hz, and extends into the true sub-bass with almost no level drop, and certainly no roll-off. Due to the rather modest and balanced bass lift as well as its quite flat extension, don’t expect any real deep, visceral rumble though.
Yep, the F9 Pro is far from basshead levels and features a quite balanced bass presentation with the right balance between a little punch and evenness, and its lows also stay out of the midrange quite nicely.

The mids are on the brighter, somewhat leaner side with a lift from 1 towards 3 kHz, something that gives them clarity and more presence in the mix and helps vocals to retain presence instead of appearing too distant, although the presentation is not exactly “in your face” either.
Balance is good, and while there definitely is some undeniable colouration towards the brighter, leaner side, they still appear mostly well-done although not fully natural, which is in the nature of this tuning that is by the way rather popular among hybrid in-ears coming from Asian manufacturers, and helps focusing on air and clarity. Nonetheless the amount of leanness in the mids, while not as bad as the Fidue A85 (the F9 Pro still has a little bit of countervailing lower midrange body and is a little less elevated in the upper mids, and the balance between subtle warmth and clarity is overall quite well-made), might become a bit annoying over time and doesn’t always fit to the singer’s voice – I would say that it works most of the time, but sometimes the vocal timbre can already appear a bit too off.

Above that, there is a lift at 5 kHz, followed by a rather strong peak at 8 kHz and really good extension past 10 kHz.
Therefore the highs are quite undeniably on the bright side and the F9 Pro is an in-ear that was rather designed for treble lovers.
While sibilance and vocal sharpness are still nicely avoided, the 5 kHz elevation adds some metallic-ness to the presentation while the 8 kHz lift tends to a bit of sharpness at times. This is still okay and tolerable for a hybrid in-ear at this price point and nothing that cannot be fixed without some EQ tweaks, however a bit more evenness and probably a headroom-generating dip around 5 kHz would have been a bit nicer for an overall more even and realistic treble presentation. It overall just feels a little “rougher” and “edgier” than comparably bright dynamic driver in-ears, giving the F9 Pro a rather “hard” and unforgiving sound in the highs.


On the technical side, the F9 Pro is a quite convincing in-ear that sounds just like what you probably wish a hybrid in-ear to sound like at this price point – clean and crisp midrange and treble with good separation, together with a bass that has got somewhat more decay and less tightness compared to most Balanced Armature woofer implementations, while still sounding quite controlled, giving it a character that most people would refer to as “natural”.
Bass definition and control are good for the price and class, albeit not as fast and tight as the iBasso IT03 that is among the fastest and tightest hybrid in-ears when it comes to bass. It doesn’t sound muddy though and also doesn’t appear disconnected from the mids and highs, so coherency is quite good (while tuning coherency could be a bit higher in the highs).
With quick bass punches and attacks, lows tend to lose a little focus, which is common for implementations that are not extremely fast and tight, but always remain distinguishable.

Separation in the mids and highs is quite precise and speech intelligibility is also good.


The F9 Pro neither disappoints nor really excels in this area – on the whole, its spatial presentation is rather average, with a somewhat wider than deep presentation while there is still noticeable front projection with surprisingly good layering that lets you discern far and close instruments as well as those in-between quite well.

Imaging is quite good too, and the “empty” space between instruments is pretty clean.


In Comparison with other hybrid Triple-Driver In-Ears:

Fidue A73:

Bass level on both in-ears will ultimately depend on how much the inner vent is covered, but nonetheless the Fidue has got the warmer and fuller lower-end presentation with more warmth and body in the root/fundamental range and lower midrange.
The FiiO is a bit brighter, leaner sounding in the midrange, with the Fidue having a gentler clarity lift in the lower highs/upper mids.
While the Fidue is already a bright in-ear in the upper highs, the FiiO’s upper treble peak is stronger and tends to more sharpness – the Fidue just has that 5 kHz dip that is necessary to generate the headroom for the peak whereas the FiiO is a bit over-energetic here.

Bass definition on the FiiO is ultimately a little higher, with the Fidue appearing a bit more layered and textured as a result of its somewhat softer, more body-focused presentation. Control is still quite comparable though.
The FiiO has got the more revealing character since it is brighter in the highs, but I’d also generally say that the FiiO is a little ahead when it comes to separation and precision in the mids and highs. Still not a large difference, but noticeable with faster and more complex music.

The Fidue has got the somewhat more open and slightly wider soundstage while imaging is comparably precise, however the FiiO has got a bit of an advantage in the end when it comes to the cleanness when portraying “empty” space between musicians and instruments.

- - -

Subjectively, I personally prefer the Fidue’s tonal tuning that is a bit less “aggressive” in the highs despite also being on the brighter side with an upper treble peak, while the FiiO offers a bit more precision and more features as well as accessories for roughly the same price.

1More E1001:

Even with fully open vents, the E1001 is bassier than the F9 Pro.
The E1001 has also got a somewhat clarity-oriented midrange tuning, but the F9 Pro is ultimately slightly leaner overall. While the E1001 has got a dip in the middle highs around 5 kHz, the F9 Pro is a bit elevated in that area.
The E1001 peaks at a higher frequency in the upper highs, with comparable but ultimately still slightly quieter levels.

In the lows, the E1001 is (audibly) softer and looser, with inferior speed and control. Therefore it feels a bit disconnected from the rest, something I criticised quite a bit in my original review. Coherency is therefore superior on the F9 Pro that also sounds noticeably better separated and focussed with complex and fast tracks.

The 1More has got the wider soundstage that also sounds a bit more open, however separation is a bit cleaner on the FiiO that also has the more precise layering.

- - -

Overall the E1001 is the easier to listen to and more mass-friendly in-ear with its u-shaped tonality, however when it comes to technical abilities and driver coherency, it ultimately loses audibly against the FiiO.


The FiiO F9 Pro offers really good value, plenty of really nice accessories, has got nice features (replaceable cables plus inline remote control) and build quality coupled with a good, quite precise technical presentation for the price and a hybrid in-ear at this price point, but ultimately lacks some realism and naturalness in the upper mids and treble that can become a bit over-energetic over time and if you don’t like a generally bright signature. Nonetheless it sounds clear, well-separated as well as detailed.

I have read many of your excellent reviews, and wanted to get your opinion on the F9 Pro as it compares to the Campfire Orion. I had the F9 SE but they were confiscated by a family member (with my blessing). I enjoyed them, and needing a replacement, began looking at available options. I saw your previous review of the Campfire Orion, and as it is one of the IEM's I am considering, hoped you might be able to provide some comments comparing the two IEM's; price differential aside. Thanks.

I've never heard let alone reviewed the Onion in-ear - could it be that you've posted your post to the wrong review of the F9 Pro? Anyway, from what I know about the Onion, it has less bass and especially treble quantity than the F9 and F9 Pro, leaning toward a flatter sound signature.
Pros: Balance EQ
Clear details
Great soundstage
Very good resolution
Cons: No non-mic version
About Me
To get started, let me tell you a little about myself.
I’m a gigging musician (lead guitar/backup vocals), an audio forensic analyst, a novice sound engineer, and an avid music lover with a wide taste in music. Being an audio forensic analyst is a plus I find when reviewing audio products simple because I know what bad audio sounds like and usually know how to correct it. My experience allows me to be familiar with the limitations of my own ears and the equipment I’m using.
For the consumers, my perspective for all my IEM reviews will be based on these things. I won’t sugar coat things or make things sound better than they are. I’m just like you and I want good value for the money I pay for any product.

To the manufacturers, I’ll always give you an option to respond to any concerns such as quality that I have during my review. I’ll contact you directly and will do so before my review is published. I want to provide an honest and tangible review for your prospective customers without being unfair to you as a manufacturer.
I’ll always be fair and my review will be based on my perspective and my experience.
Now on to the important stuff.

About the product/expectations
I received these on loan during a Fiio Review Tour. I really had no expectations going into this except that I believed the F9 Pro would be a competitor in the $150 price range.

The F9 Pro is built like a tank, metal housing is plus. The cables seem to be good quality, but there was no non-mic 3.5mm cable available.

After using them for a few days the comfort is very good. The shape of them seems very similar to the Shure SE IEM's and they seat in my ears very similar. Because the housing is metal, they are a bit heavy and when used as a stage monitor, you may have to reseat them after a few songs. Overall they're a good fit.

The sound on these is outstanding. For the price point that these come in at, most manufacturers are going to have a hard time beating the F9 Pro.

The lows are clear and tight with a very natural decay. I didn't find any inbalances here and the low end extension resolves well below 20hz. The bottom end never gets in the way of the mids and has enough punch that even bass heads will like these. However the low end seems very balanced and not overly emphasized.

The mids are are very good with a natural feel. Vocals shine through very well and the mids contribute to a beautifully balanced sound stage. Great separation and ability to resolve different instruments. The mids may sit just a hair behind the high's depending on the source but are still very present and balanced.

The highs are clear and detailed. No harshness or sibilance that I could detect, very natural sounding with a bit of extension that contributes to the overall clarity of the sound and helps to widen the sound stage. very balanced sounding.

Compared to UE900s, I found the F9 Pro to have a very similar soundstage, but with more clarity and less low end emphasis. The low end of the F9 Pro seemed to be almost as abundant as the UE900s but with more resolution. The mids and high end was very similar but the F9 Pro had a bit more high end extension which helped to put the F9 Pro just a slight edge on the UE900's for clarity.

I compared these to the Primo8 and found that the F9 Pro had a more balanced sound, but like the Primo8 depended on the source. The Primo8 sounds very good when using my Samsung Note 8 straight, but the F9 Pro needed a bit more power than my phone could provide I believe. I coupled the Fiio A3 with my phone and the F9 Pro blossomed into one of the best sounding IEM's that I've had the pleasure of using and easily outperformed the Primo8 in everything except mids which is where the Primo8 really shines.

Based on my findings, I felt these were possibly a top choice IEM for anyone looking for a balanced sound.

Isolation was good but could have been a little better. I used the provided tips and all of them seemed to seal very good for me. I then used a cheaper "Kinden" foam tip for the majority of my testing due to being able to get a great seal for me.

I hesitate when trying to gauge value in any product unless there are issues with build quality or the product is just an outstanding value. Based on the $139 price tag as of the time of this review, I would rank the F9 Pro at the top in this price range. I haven't heard anything that will beat them as of yet.

The Fiio F9 Pro is an outstanding IEM and you would be hard pressed to find another IEM that does as well in this price range. The overall balanced sound, the soundstage and resolution of the F9 Pro is outstanding and I truly believe that is an understatement. The fact that they give you a very well made hard case a decent soft case along with 2 cables (1 3.5mm mic cable, 1 2.5mm balanced cable) and a host of 4 different types of ear tips make these an exceptional value but all of that is overshadowed by the sound quality. Fiio hit a home run with the F9 Pro.
Pros: Fiio flagship with both power handling, spacious presentation, and heighten clarity.
Cons: I could not find a weakness.
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F9pro review

Welcome to this review. I participated in the headfi tour for the Fiio's flagship hybrid ear phone the F9 Pro; one dynamic driver and two knowles balance armature drivers. And I am writing this review after having spent some time listening to the F9 Pro in my unique way. As the F9 Pro is the newest and the most advanced ear phone to date that I have encountered, I approach this review with a challenge to myself that I would find something to point out in both camps, positive and negative. And what I discovered was that filling the positive camp with observations was easy. But filling the negative camp was not so much as easy. In fact I will explain what happened shortly. The overall rating of this precision engineered F9 Pro is a resounding thumbs up and a recommendation that goes as far as to say life is too short "have cake and eat it too," I'm just saying.

Ok, where do I begin? Instead of the organized and methodical approach to analyzing like in a school textbook, lets just go all over the place. I say this because the F9 Pro is great at projecting the sound presentation all over the place. It creates a listening environment that is so much like listening to big headphones and even speakers, I am amazed. This to me is very appreciative on a number of levels. For one, I found a headphone that does not mess up my hair in the F9 Pro. And second, bigger is better when it comes to sound, but F9 Pro does this with even more desirable qualities that headphones and speakers simply can not match; i.e. noise isolation, clarity, portability, and so on. Speaking of positives, I could prolly go on and on about the balance armature that there are two knowles and they bring very excellent clarity, separation, and coherence with the rest of the sound presentation. Music with a lot going on is presented like F9 Pro is not breaking a sweat delivering the nuances of the subtle details in each and every sound in the music. In another words, no mud can be found here. I really was impressed how the details in the voices and the strings became evident; where all of the details that a microphone can pick up, the F9 Pro delivers untarnished. And another important factor to mention is how well F9 Pro gets along in the community. For explanation please feel free to continue to the next section.

The F9 Pro can be enjoyable to listen with or without a dedicated amp/dac. At 28 ohms the F9 Pro can be driven easily by an iPad mini and deliver quality sound. But like all enthusiasts, you should not settle for just good enough. In this field of interest, you should seek out what sounds the best with what you can gain access to, reasonably. And I found out that the F9 Pro had skills. It had skills to be transparent; at least enough to preserve the sound signature of an amp/dac. Ideally both the amp/dac and headphones should be transparent to deliver the source music as intended just like it was at the recording. Anyway my Accessport can be bright and my Walnut V2.1 is warm. And when the F9 Pro was connected to the Accessport, the sounds came through with brightness. And when the F9 Pro was connected to the Walnut, the sound came through with warmth and tenderness; so I did what anyone member of headfi would, turn up the volume. Let me tell you the F9 Pro is a blast to play loud. Because it is so poised at maintaining its resolve; it's impressive. Now there is an inside baseball going on with the Walnut as far as balance armature is concerned. Basically Walnut's high output impedance, like 100 ohms, suppose to sound bad with balance armatures. Apparently the F9 Pro breaks free from this convention and goes where no other balance armatured equipped earphones have gone. Bcause F9 Pro sounds amazing with the Walnut V2.1.

Back in the day I used to buy a lot of music compilations; this was a period after the mixed tapes era. In those days a lot of mixes were thrown in with the more commonly heard format, the "Radio Edit" version. I suppose those mixes included unique sound manipulations, but who had time to go through them all. So now here I am using my ipad, but some hackers is adding distortion to my right channel. So I took to summoning my savvy intuition and adapted. I pulled out my music and let it lose on the F9 Pro connected to the Walnut as amp and the Benjie X1 as source/dac in shuffle mode. Since I haven't heard a lot of the mixes, this experience was more than entertaining; it was discovery and I was excited. But more importantly I was blown away at how good the F9 Pro was in delivering the music. Everything sounded fresh and new like I have never heard before; hearing things in the music in a way that I have never heard before. In essence the F9 Pro made it seem like I bought a whole lot of new music. And from an economist point of view I'm saving a lot of money getting the F9 Pro. I know right, economist knows how to get us into financial trouble; cause often they're only right half of the time, but I digress.

Some break down info in a quickie format:

Bass: F9 Pro has mid bass, regular bass, and sub bass no questions asked. But it does not have basshead bass that is always there on everything you play, unless you play only basshead music. In fact the bass has quality in the form of distinction in the bass band, never muddy. I like.

Mids: F9 Pro is clear with great separation in the mids. Voices and instruments can be very revealing with the right setup. I like.

Treble: F9 Pro has the means to deliver the treble honestly, but I prefer to tone down the brightness for the sake of longevity. And depending on the amp/dac used F9 Pro can be versatile and deliver the sound signature that I want. And F9 Pro is good in this way. I like.

Negative camp:
I tried my hardest to find a weakness in the F9 Pro by using the gear that I have, but to no avail. I concluded either there is no weakness to be found or I simply need better gear to evaluate F9 Pro better.

On a different note, this is negative camp for me because I reviewed the Fiio Q1 MK II which I thought was great in the balance mode. However I did not have access to this amp during this review. And therefore I can only imagine how much greater the F9 Pro could have brought to my listening experience in the balance mode. Especially knowing that the F9 Pro is great at handling power and space at the same time.

On a related note, I could not verify the mic and volume up and down button due to hacking on my ipad mini.

Fiio has improved upon the F9 with the F9 Pro and I trust it is so. Because my evaluation of the F9 Pro is that it is truely worthy of its flagship status. F9 Pro does everything well. And I learned my inventory of gear can not find a fault with the F9 Pro. It is that good. So I apologize to the reader as I have failed to reveal a weakness in the F9 Pro.
Thank you so much for the nice review. Yes, the F9 PRO is not MFi certified, so the volume is not valid using on iOS system. With the removal of 3.5mm port on new iPhone, to get the MFi certification that may only available to iPhone 6s and former version, but will result in longer delivery time and higher cost, so we have no choice but to made the compromise.
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Pros: They fixed the glitch! No more spike at 7 kHz. Excellent build, good extension at both ends, nice listenable signature.
Cons: Treble still a bit hot. Tuning tips muddy the sound and are not particularly useful.
A big thank you to Fiio for including me in this review tour. As I write this, the F9 Pro is waiting for the PO to head to the next lucky tour member.


Fiio and I have grown up together. Some of my first audio gear had the Fiio name on the side of it. An E17 with an E09 graced my office desk for quite some time a few years ago. As Fiio has matured, so have their products. Their DAPs are now the standard by which any sub $500 DAP is measured if you look at all the comparisons they draw in reviews. Not too long ago, I was asked to review a first for Fiio, an earbud. They had added the rest of the equation to their product line as they had long had amplifiers, digital to analog converters, and digital audio players, it was time to add earphones. That initial earbud was a great listen and was a hint at things to come. First, they paired with Dunu to release the EX1, their version of the Titan. I skipped that one, as I already owned a Titan and did not see a need for another. Then came a brand new line the F series. The F1,3,and 5 are all dynamic driver based and as you go up in sequence the resolving power of the drivers also move up. I purchased the F5, which was an improved EX with a titanium diaphragm and improved extension on both ends. They did a good job of showing what Fiio had learned from the earlier generations. Next was their BA/Dynamic hybrid the F9. After having liked the F5, I wasted little time in placing an order for the F9 only to be a bit disappointed. While the F9 had good clarity, more than expected levels of detail and good extension, it also had a major problem. A treble spike in the middle of the lower treble range absolutely ruined an otherwise good experience. Therefore, the F9 sits in the drawer while I moved on to the Brainwavz b400. Then Fiio announced the F9 SE – which was a fixed cable budget version of the F9 with no other changes. Then I was reading one day and a Fiio representative had posted on the upcoming release of the F9Pro, which got my attention, as the change was the in-house BA was replaced with the Knowles TWFK-30017 BA. My immediate thought was “Will this fix the spike?” Luckily, for me, Fiio sent me a sample of the F9Pro as part of their review tour. Did they succeed – read on?


The F9 Pro comes with a very complete kit. Starting with a premium feel to the packaging. The box has an outer cardboard box with typical western style product details and advertising.


Inside the outer box is a black pressboard case with an understated Fiio Logo. Opening the box reveals well-fitted compartments for the earpieces at the top and a pelican style hard case below it.

Tips are hiding under the earpieces and quite a selection is provided (three different sizes of four different styles of tips) (More on this below). Inside the Hard case is a soft case made of something close to sweatshirt material, and two cables. The hard case is well padded and is similar to the Dunu provided pelican cases, which may hint that a partnership between Dunu and Fiio is still lurking in the background.


While well designed to provide protection from water and abuse, the hard case is too large for pocket carry so the soft case is a much-appreciated addition to the accessory package.


A 3.5mm terminated single ended cable with a microphone and remote and a 2.5mm terminated balanced cable devoid of the mic/remote are provided and hiding under the tips. (Personal bias is for cables without remotes so I used that most of the time unless testing the mic/remote.)

Tips deserve their own conversation here as the tips provided are designed to do different things. Fiio provides a set of memory foam tips that have the typical effect of dampening treble a bit and providing great isolation. In addition to the foams, three styles of silicone tips are provided. One style provides a neutral signature while the other two enhance either bass or treble. All my testing has been done with either neutral or foams (I did not use the provided foams since this was a review tour).


The F9 series all share the same 2 piece metal shell. It is well made with seams being very consistent and no major gaps or glue showing. All of the F9 variants with removable cables use an mmcx connector for cable attachment on the upper side of the housing. This does limit the design to over-ear cable wear with the provided cables due to the built in guides. After-market mmcx cables without a memory wire can allow cable down wear but the fit is sub-optimal, as the weight of the cable tends to pull on the upper side of the shell and cause problems with seal and isolation. There are two vents on the inside of the shell (one immediately behind the nozzle and one immediately beneath the mmcx base). These do somewhat limit isolation but wear in a noisy office or public transport is still very viable.

The mmcx connector is at a slightly greater angle than the F9 so cables with larger connectors (Veclan) now fit well. (On the original F9, you had to shave some connectors to get a proper fit). Red and blue markings exist on the body of the mmcx connectors with matching coloration on the tip of the cables for easy reference.

Cables themselves are well made with solid rubber housing around the mmcx with a colored ring to show left/right orientation. Plastic memory guides provide the strain relief, which is a much better arrangement than memory wires in my opinion. Gentle heat with a hair-dryer will allow for reshaping should it be desired. Cables themselves are supple and minimize microphonics well. There is no chin slider, which I’m sure will be a detractor to some, but I found it unnecessary as fit, was good without it and no issues with movement presented during use. The splitter is metal and colored to match the earpieces with the word pro in white lettering.

A strain relief is added at the lower side of the splitter. The cables terminate in a 90 Degree 2.5 or a 3.5mm jack.


The 2.5mm cable is braided all the way throughout while the 3.5 is cloth wrapped. Both cables have cable management ties made of soft rubber just above the jack. This is a welcome addition and I found the soft rubber was easy to ignore if not in use. For those that dislike them a quick and careful cut with a razor knife should have them gone in a matter of a moment.

The Mic/remote on the 3.5mm cable matches the color of the earpieces as well and is straightforward and simple to use. It is worth noting that the microphone is susceptible to movement noise due to its position on the backside of the remote where it will be directed toward your clothing during normal wear. A shirt clip would be advisable if you intend to use the phone while at the gym or other strenuous exercise to minimize this.

The color of the F9 pro is much closer to that of The X5iii and the A5 I recently reviewed so if that is something that concerns you, you can rejoice. The original F9 was a distinct mismatch in this department but was never a concern for me.

I found the fit of the F9 pro to be very similar to the original F9 with a slightly greater forward rake to the nozzle than the original. Isolation was good but very tip dependent, as they are not a super deep fit.


Let us go ahead and get it out of the way. Did they fix the spike? The answer is maybe. The spike has moved up the scale from the 7 kHz region of the original F9. My guess would put it at high 8 kHz / low 9 kHz range based on what EQ settings remove it. The great news is, it is much less obtrusive than the previous version to my ear and probably many others. The bad news is technically, there is still a spike and it still contributes to the overall sound signature. Having said that, I am very pleased with the improvements the Knowles drivers made to the F9 Pro and I think it is big improvement in the treble overall.

For me, I like a headphone/earphone to have a good sub-bass presence, moderate mid-bass with as little bleed into the mids as possible, slightly forward upper mids with good vocals, and enough air and sparkle to get my attention. I tend to lean toward bright signatures as long as sub-bass is present.

The F9 Pro nearly matches my preferred signature. It is nearly linear with a mild U shape with plenty of sparkle without being belligerent. Bass is enhanced beyond neutral, but not emphasized to the degree commonly seen in V shaped signatures. Mids are clear with lower mids being very slightly recessed but upper mids pushed slightly forward almost exactly in the presence region so vocals are well rendered and natural sounding.


I expected the F9 Pro to share the same bass as the F9. Let me say immediately, it does not. This may be a case of addition by subtraction as the change in the treble elements may have revealed more of the bass, but the Pro has a more pronounced sub-bass and lower bass without being bloated in the mid-bass region. The F9 Pro’s bass seems to have greater extension and retains the good punch and slam of its progenitor. The mid-bass is very slightly forward but bleed into the mids is minimal. My advice would be to avoid the bass enhancing tips as they only serve to bloat an otherwise very good bass.


The lower mids are slightly recessed or maybe it is because the upper-mids are slightly forward the lower range seems recessed. Female vocals benefit greatly from the slight push to the upper mids while Male vocals sound full and natural. I was particularly impressed with the rendering of Van Morrison’s vocals (One of my heroes). Guitars have a nice full-bodied tone without being bloated and while retaining great definition and detail. Although, not a warm signature, the mids do have some elements that produce a smooth, organic tone more typically found in warmer signatures.


I was not a fan of the original F9’s treble. Unfortunately for me, the spike at 7 kHz was in a range that absolutely fatigued my ears and ruined the experience in short order. I understand that others were not bothered by this and my wife was amongst them. She uses my F9 infinitely more than I do these days as a result. I borrowed them back long enough to compare and make sure my memory was correct. What I found was the Pro has a more domesticated treble with better table manners. The lower treble is more linear when compared to the F9 with a mild boost in the mid treble that leads to a bit of extra energy for cymbals. The tuning is enough better on the Pro that more detail is presented (probably addition by subtraction again) when compared with the F9 and extension is slightly better with a bit more air and sparkle.

Imaging and Soundstage

I found imaging on the F9 Pro to be quite good as directional cues are well presented and the pro does a good job of layering without losing those directional cues in busier passages. Soundstage is wider than it is deep and is above average for its class.


The F9 Pro works well from my HTC M9 or I-phone 7 without an external amplifier, but I did find it scaled well and was particularly enjoyable using the Cayin N3 and a resistor modded Walnut F1 (18K Ohm in parallel with Muses op-amp to lower gain). I think the F9 Pro also is easier to pair than the original F9 due to a slightly warmer tone.


Fiio F9: The obvious aside (ergonomics etc. being equal), the biggest difference in the PRO is the sound signature. The Treble spike that intruded into listening is gone on the Pro and the whole signature opens up as a result. Sub-bass is more present, mids are a bit more forward, and vocals are natural and well rendered. The strident and sometimes sibilant nature of the F9 is resolved in the F9 Pro and makes the listening experience much more enjoyable.

B400: The brainwavz has been a daily driver for me, so the question is, can the F9 Pro unseat it? From a fit and finish prospective, the F9 Pro gets the nod, as its metal shell and finish are about as comfortable as the b400, but the peeling paint on the seams of the 400 are a reminder that the construction methods differ quite a bit. From a sound perspective, the two are very hard to compare as the b400 is near reference flat and the F9 Pro is much more U shaped. The b400 shows a bit warmer signature compared to the F9 Pro’s bright leanings. Both have good extension although the F9 may have just a hair better extension at the low end. That said the b400 definitely wins on speed. Attack and decay are tighter and details benefit accordingly. With these two, it is going to come down to preference and you cannot go wrong with either. I love my b400s, but will make a place in my routine for the F9 Pro as well.

AKG n40: The n40 is more compact than the F9 Pro but fit and isolation are about the same. Both are designed for over-ear cable wear and both use very similar designs to the shells with ports to the inside of the shell. The F9 Pro has more low-end slam, while the n40 has slightly better extension at the top end. Signatures are very different with the F9 being much more aggressive and the n40 being much more laid back. The n40 lacks some of the detail in the upper mids of the F9 and has slightly less sparkle in the top end but more air at the very top. The n40 provides a very non-fatiguing listening experience while the F9 Pro brings additional details to the surface at the expense of a slightly harsher listen. I think owners of the b400 or F9 pro may find the n40 a bit of a disappointment as it has little in the way of technical enhancements over the others at nearly double the price.

Magaosi K5: The K5 is nearly as resolving as the F9 Pro but suffers from a low-level hiss when paired with high-powered sources. When run from a source it pairs well with, the K5 is a bit warmer than the F9 Pro. Where the K5 really loses, ground is in bass extension. The F9 Pro has considerably deeper bass and much more sub-bass presence. Considering the F9 Pro has a suggested retail $30 below that of the K5 there is really no reason to consider the K5. The F9 Pro is a marked improvement over the K5 in nearly every category.

1More Quad: Build quality is a wash or a very slight advantage for the one more Quad. The F9 Pro has a big advantage when it comes to fit and isolation though due to the odd shape and weight distribution of the Quad. Removable cables are another plus for the F9 Pro. Signatures are very different with the Quad being warm and dark while the F9 Pro is brighter if a bit thinner. The Quad tends to have a bit bloated upper bass which can at times bleed into the lower mids. This gives the F9 Pro a distinct advantage in definition and clarity while the mids of the Quad can seem a bit cloudy or murky at times. The Upper end of the signature is also very different. The Quad is more laid-back while the F9 Pro is a bit more forward and aggressive on the upper end. Extension on the upper end is better on the F9 Pro which gives it an overall cleaner more transparent signature that presents more detail than the Quad. Technically, the F9 Pro is the better choice, its hard to knock the Quad though as while it lacks some of the transparency of the F9 Pro it has a very listenable signature. If you wear them on the go, the F9 is a clear winner as the weight distribution of the quad makes them tough to wear while moving and maintain a good fit.

Trinity Icarus III: I used an Icarus III with the green nozzles as my daily driver for a good while and with price points being similar (pre-order) I thought I would include them here. Cables – F9 Pro wins hands down. I much prefer the cable style of the F9 to that of the Icarus. Sound wise, the Icarus is much warmer compared to the bright signature of the F9 Pro. Even when using lean filters, the Icarus tends to have some bass bleed into the upper mids and suffers from lack of details in the mids because of being obscured by the bass bump. The plus for the Icarus is more bass slam and better bass extension. The Icarus can be a bass monster depending on filters while the F9 pro renders more detail and is much more neutral.



I had high hopes for the F9 Pro as the F9 checked a lot of the right boxes for me, but having recently purchased the b400, AKG n40, and the F9, I was reluctant to spend more to purchase the F9 Pro on the chance that it was enough improved when compared to the original F9 to warrant the purchase. Having now had the opportunity to use the F9 Pro for a week as part of this tour, I can say I should not have been reluctant to purchase the F9 Pro in the least. The F9 Pro easily ranks among the best in-ears I have tried in the sub $300 price range. The things the F9 did well are still there and some are improved. The things the F9 did poorly have been addressed and are no longer issues. Bravo to Fiio for listening to customer feedback and making the changes. Fiio has done what some would have said was impossible, gone from startup earphone maker to class-leading performance in less than 24 months. I cannot wait to see what is next from Fiio. Maybe an over-ear?


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Pros: Great build and ergonomic, Excellent treble extension, Detailed, Relatively balanced, Tuning tips
Cons: May still be too bright for some, Average isolation, Still not especially linear
Introduction –

Fiio have grown from a small manufacturer to an industry juggernaut in the span of just a few years due to their competitive pricing, eye-catching designs and consistent performance. Their myriad source devices played an integral role in their popularisation but with competition filling the market to saturation, it is clear that other innovations represent the next evolution of Fiio. The F9 was that essential Fiio in-ear for the vast majority, an earphone that thrived on clarity and detail presence.

However, that earphone also had critic dividing flaws, most notably, a treble spike within the lower treble that could make it sound quite unnatural. As such, Fiio have produced the F9 Pro, a continuation of original utilising the same triple hybrid driver setup but with improved balanced armature high-frequency drivers. This is an interesting progression of the F9 and certainly a step in the right direction while retaining a lot of the charm of the original. Let’s see whether the Pro’s refinements justify its increased $145 asking price.

Disclaimer –

I would like to thank Sunny from Fiio very much for her quick communication and for providing me with the F9 Pro for the purpose of review. All words are my own and there is no monetary incentive for a positive review. Despite receiving the earphones free of cost, I will attempt to be as objective as possible in my evaluation.

Accessories –

The F9 Pro has a comprehensive unboxing congruent with Fiio’s other offerings. The earphones come with a bolstered accessory set when compared to the original model, comprising of the same terrific pelican style hard case in addition to a plethora of ear tips. Fiio also provide a small zippered fabric case that is far more portable, not to mention pocketable.

Regarding tip choice, Fiio include various types of tips, each with their own distinct sound; 3 pairs of bass eQ tips, 3 pairs of standard tips and 3 pairs of firmer, brighter tips. Fiio also include 3 pairs of one-size fits all memory foam tips that dampen the treble slightly and provide greater noise isolation. Underneath are the two cables, a braided balanced unit and a regular 3.5mm cable with a remote/mic.

Design –

The original F9 was an impressively constructed earphone and the Pro is mostly identical but with subtle tweaks that elevate the user experience. The most noticeable change stems from the Pro’s new colour scheme, assuming a lighter, bluer hue of grey that better coordinates with Fiio’s sources. The MMCX angle has also been adjusted, now accommodating cables with bulkier MMCX connectors such as the Penon OS849. In addition, the Pro has coloured indicators on the inner face of each earpiece that enables easy orientation.

Otherwise, the experience is very much the same, the F9 Pro carries a solid aluminium build with a satin texture. Ripples propagate along its face producing a very dynamic aesthetic in addition to some additional tactility when swapping cables. The earphones are smoothly formed and ergonomic with a medium fit depth. They have a perfectly angled stem with a lipped nozzle fitting the majority of ear tips such as Sony Hybrids and Spinfits.

Due to a multitude of vents on the inner face of each earpiece, the F9 Pro provides just average levels of isolation, just sufficient for public transport but they’ll get drowned out in louder environments. They are relatively low-profile and can be slept in comfortably, they also produce average amounts of wind noise despite their rippled texture. The F9 Pro wears comfortably, with a minor ache forming at the rear of my ears after several hours due to their slightly larger dimensions.

The F9 Pro utilises a removable MMCX cable system. The connectors are very tight and clicky, and though my left earpiece was notably looser than my right one, this didn’t produce any intermittency. It would seem that Fiio have appended the issues that afflicted the F5. The standard remote cable is mediocre, rubbery and thin with adequately relieved terminations. The mic is quite clear and the buttons worked perfectly on both my HTC U11 and iPod Touch 6G. The balanced cable is a lot nicer, however, with a 4-wire braid and smooth, incredibly supple sheathing. The cable has nice metal connectors with an improved right-angle plug that is far better relieved than that on the F9. The earguides are pre-formed rather than using memory wire, they were well shaped and stable for my ears.

Sound –

Tonality –

With a more linear treble response, the F9 Pro forgoes the analytical v-shaped signature of the original in favour of a more balanced u-shaped tonality with more tasteful brightness. Bass is enhanced over neutral but rarely becomes the focus of the sound while mids are clear and well-present, especially with regards to upper mids. Treble is emphasized with a notable lower treble hump though the F9 Pro avoids becoming over-forward within the higher-frequencies as the original could. Considering Fiio’s asking price, this is a very nicely balanced take on a brighter signature and one that is well-compensated by tasteful bass enhancements. They are immediately more natural and balanced than the original model, not to mention, the vast majority of competitors sitting around the $100 mark.

Bass –

The F9 Pro’s low-end delivers relatively agile notes with nice punch and slam. Bass is skewed warm and its quantity is slightly lifted though never to the extent that balance and control are compromised. Interestingly, the Pro differs noticeably from the original F9 despite using the same dynamic driver. This is most likely a result of reduced treble colouration, with more restrained treble emphasis netting increased overall balance and subjectively greater perceived bass emphasis. So where the original F9 was mid-bass orientated and more reserved in its tuning, the more balanced Pro has perceptibly more bass depth and sub-bass impact if similar extension. Upper-bass is also elevated to a small degree, producing a slightly organic but otherwise uncoloured lower-midrange presentation.

By lowering the treble as opposed to boosting the Pro’s bass, the new F9 manages to sound appreciably fuller without compromising nuance, in fact, it’s quite the opposite. Due to greater linearity, bass has more density and body without sounding overly warm, thereby keeping bloat in check. Though sub-bass is still a little slow, this tuning does create more defined bass notes with reduced mid-bass focus enabling greater detail to shine through. As a result, though similar to its progenitor, the Pro represents a step up in quality with more accurate texture and tone. Through these alterations, the Pro sounds more natural and linear into the midrange frequencies in addition to sounding cleaner and more defined within the lower registers.

Mids –

With a slightly brighter signature, the F9 Pro focusses on clarity and energy over dynamics and body but it remains a remarkably accurate performer overall. The Pro is immediately more natural than its predecessor due to reduced treble colouration and relatively increased bass presence; they no longer require the adjustment period of the F9, simply sounding correct. Some clarity is compromised, but the F9 Pro produces a far more neutrally bodied and discerning presentation than before while remaining clear and immediate. Male vocals sit slightly behind, though the lower midrange is quite transparent and accurately bodied with bass spill being a non-issue. Lower midrange elements such as piano and guitar are full without becoming tubby producing defined and well-delineated notes. Though not an especially warm earphone, some tinges are present which grants the Pro with a slightly more organic lower midrange presentation.

Upper mids tell a similar story, higher elements are slightly forward with more clearly enhanced clarity, but vocals never encroach upon fatigue or stridence. Again, the Pro’s more linear treble tuning creates more accurately voiced vocals, alleviating the unnatural presentation of the original almost entirely. As a result, the Pro really excels with female vocals that are clear and sweet with great projection and resolution. The Pro also has a far smoother upper-midrange to lower-treble transition that greatly aids detailing and separation as the finer details are no longer overshadowed. Resultantly, the Pro not only retrieves more background detail, but foreground details are presented with greater realism and separation, creating a sound that is appreciably more nuanced and considerably more musical.

Treble –

The original F9 swung hard with its treble, some would say it was even a little ham-fisted in its approach. That said, it was still a well-detailed and resolving earphone that was mainly let down by its isolated lower-treble spike. The Pro isn’t much darker rather, treble is just slightly more restrained in emphasis and that emphasis itself extends over a larger range of frequencies. As a result, treble is more linear, lacking most of the peakiness of the original, and highs are more bodied and realistic if similarly forward in the mix. These improvements begin with the lower treble that retains the same aggressive detailing of the original with an extra layer of cleanliness and separation on top. Guitars are very crisp with great attack and resolution of micro-details, and cymbals, though still slightly thin, are well textured with pleasing decay.

The F9 Pro’s treble emphasis declines smoothly into a linearly extending middle and upper treble, granting the Pro great air and consistent instrument placement. Through this, the Pro also avoids sounding overly busy or crunchy within the higher frequencies when listening to complex tracks. Extension is very impressive considering Fiio’s asking price and a noticeable improvement over the original, contributing to heightened separation and micro detailing throughout. High-hats, in particular, are delivered with accurate shimmer and notes within the highest registers avoid truncation. Instruments are also presented with copious air and treble remains linear into the upper registers if with slightly less accentuation than lower treble elements. Treble has great resolution and clarity while remaining cohesive and the F9 Pro achieves its nuance not through exaggeration of a particular frequency zone, but through terrific quality and extension.

Soundstage, Imaging and Separation –

The F9 Pro produces a well-sized stage that reaches to the periphery of the head but very rarely extends beyond. They combine great width with nice depth to create a multi-faceted if not totally immersive presentation. Imaging is notably improved over the F9 as is separation on account of the Pro’s more balanced, extended sound. The Pro’s enhanced clarity and upper midrange/treble energy deliver directional cues with great accuracy and a strong centre image. The F9 Pro’s relatively uncoloured sound produces defined layers that weave a coherent and accurate presentation.

Drivability –

The F9 Pro retains the same 28-ohm impedance and 106dB sensitivity of the original making it similarly easy to drive. As with the F9, it isn’t overly sensitive to hiss, essentially silent from the balanced output of my X7 II w/AM3A in addition to my HTC U11. It delivers plenty of volume from portable sources with adequate sensitivity to compensate for louder environments. The Pro isn’t overly affected by output impedance but its resolving nature does enable it to benefit from a similarly resolving source. That said, the Pro’s more natural sound makes it notably less particular about source synergy than its predecessor; so where I preferred to run the F9 from my warmer Chord Mojo and Alien+, the more neutral tones of the X7 II provided the most transparent pairing with the Pro. Fiio are also pushing balanced connectivity with the F9 Pro, I noted similar changes with slightly more separation and space though again, this could be due to the fact that the balanced cable is notably enhanced over the regular 3.5mm remote cable.

Comparisons –

Fiio F9 ($100): Both are similar in design with identical ergonomics. Of note, the Pro assumes the design of later revision F9’s. Unsurprisingly, the Pro also sounds similar to its progenitor and the most immediate differences stem from the treble response which isn’t as peaked on the Pro. As a result, the Pro is more balanced, notably smoother and more bodied. Bass slam is relatively increased and lows are both fuller and more defined overall due to lesser mid-bass focus. Mids are similarly present and both carry a more clarity orientated sound. However, the Pro has greater body and sounds considerably more natural and less sibilant due to its more linear nature.

Lower mids have notably increased body, making instruments sound a lot more realistic in timbre. Within the higher-frequencies, the Pro is immediately more detailed and more separated while remaining revealing, clear and airy. Extension is improved and the highest notes are far better resolved. The Pro produces a similarly sized stage but imaging is improved and separation is just as strong. The differences aren’t enormous (and, for that matter, neither is the price jump) but they do culminate to produce a notably enhanced listen.

Simgot EN700 Pro ($150): The Simgot is a much larger earphone but one that finds a similarly comfortable fit. Neither isolate well, both sport a removable cable but the Simgot 8-core unit looks and feels more substantial while remaining practical. The EN700 Pro is the smoother, warmer and more laid-back earphone while the F9 Pro is more u-shaped and engaging. The F9 Pro delivers firmer sub-bass slam while the EN700 Pro focusses on greater mid and upper-bass body and is warmer in tone as a result. The F9 Pro has a tighter bass response with a more neutral tone possessing greater transience and higher definition. The F9 Pro has a slightly drier, more recessed lower midrange while the EN700 Pro sounds a little clearer and a little more present but also warmer and more bodied.

The F9 Pro delivers a clearer, more present upper midrange. Female vocals sound more immediate but both are very clear yet naturally voiced. The F9 Pro delivers notes with greater attack while the EN700 Pro leans towards the smoother side with a more refined treble response. The F9 Pro is unsurprisingly crisper and brings micro-details more to the fore while the EN700 Pro is well-detailed but less concise in its delivery. The F9 Pro has better treble extension and far greater air up top but it may fatigue those unacclimatized to a brighter signature. Despite this, the EN700 Pro is notably more spacious, perhaps on account of its design. Both image very well, the F9 Pro has better separation. The Fiio will suit analytical listeners, the Simgot is more musical and listenable long-term.

Meeaudio Pinnacle P1 ($200): The P1 is smaller and produces a more stable, isolating fit. It has a solid removable cable and can be worn both cable up and down. The Meeaudio pursues a similar brighter tuning but it is less linear than the F9 Pro and slightly more engaging. Sub-bass extension is better on the F9 Pro and sub-bass impact is greater. The P1 produces a notably warmer mid-bass response yet it is tight, agile and well-controlled, delivering more defined notes than the Fiio with greater punch. Lower mids are more scooped on the P1 but both are similarly clear and defined. The P1 sounds slightly more organic due to its increased warmth. Upper mids have similar presence but the F9 Pro has greater clarity at the cost of realism where the P1 is more refined and nuanced in its delivery. The P1 has a similarly boosted lower treble response, it isn’t quite as bright as the F9 Pro, but also isn’t as linear into the higher frequencies.

As a result, they both retrieve similar details with similar aggression, the P1 has perhaps even greater attack but this does comprise texture and realism. The P1 smooths off above again, like the F9 Pro, and both extend very well. That said, the F9 Pro is more linear and resolving within the upper registers. The P1 has a wider stage than the F9 Pro while the Fiio has more depth. The P1’s greater speed and midrange resolution grant it with similarly accurate imaging, but the more vivid Fiio does separate a little better. Both are incredibly resolving earphones considering their asking price, the P1 has superior ergonomics and sounds a little more natural within its midrange while the F9 Pro is more resolving up top.

1More Quad Driver ($200): The 1More is more meticulous in its construction but the F9 Pro holds a large ergonomic and isolation advantage. It also has a removable cable that the Quad Drive lacks. The 1More Quad Driver is warmer, more bodied and darker throughout. It has more bass emphasis with a tighter sub-bass impact mated to larger mid-bass slam, imbuing its presentation with warmth and body. The Quad-Driver also has greater upper bass elevation, it sounds tubbier, slower and less defined but also denser and more impactful. Lower mids are warm yet well-defined on the 1More, they are a little more present than the F9 Pro but lack the same clarity and transparency. Upper mids are very different, the 1More is darker and thicker, female vocals are far more laid-back but still possess nice layering and resolution.

The F9 Pro is more forward with far greater clarity and aggression into its lower-treble. The Quad-Driver has a considerably more laid-back lower-treble response that sounds crisp but lacks a lot of attack and foreground detail in comparison to the Fiio. The 1More has a spiked middle treble that can sound a little tizzy where the F9 Pro is more linear. The F9 Pro has better extension despite its lower driver count and treble is considerably more resolving and defined than the 1More overall. Both construct a large stage, the Fiio is a little larger though the 1More sounds very multidimensional, quite a unique trait to this earphone. On the contrary, the clearer, more neutral Fiio separates a lot better. The Fiio is easily the more technical earphone but the 1More’s smoother sound is less fatiguing and it has a more standard fit.

Verdict –

Though almost identical on the surface, some small but very intentional tweaks here and there produce a considerably more compelling experience than previous models. With slightly updated cosmetics and a more practical MMCX solution, the new Pro is also more pragmatic than ever before. The biggest upgrades no doubt arise in listening where the Pro’s wider band treble emphasis and more balanced, linear tuning create a notably more discerning listen. And despite their increased price, the Pro ends up being far better equipped than the regular F9 to challenge similarly priced competitors, representing a fine step up from the heavy hitters in the $100 category.

Because I have no hesitation donning the F9 Pro one of the most technically impressive earphones I’ve heard around this price; achieving clarity through resolution, separation and air through extension and engagement through transience rather than relying on unnatural peaks and troughs. Of course, the F9 Pro isn’t without its issues, they still don’t isolate especially well, their tubbier housings aren’t perfectly comfortable and their revealing signature comes at the cost of outright realism and some fatigue over time, but Fiio’s latest competes head-on with some highly regarded earphones one price class up.

Verdict – 9/10, The F9 Pro, though still bright and aggressive, isn’t quite so analytical as its predecessor with hints of additional body, warmth and smoothness soothing the aggression of its revealing tonality. It is not only a resolving earphone, but an engaging one, just don’t expect an aboslutely natural or musical presentation.

Thanks for reading! If you enjoyed my review, please see my website for more just like it:
Pros: Sound quality, build quality, overall design, balance, fit, comfort, value, balanced and SE cables, accessories
Cons: Very slightly over energetic lower treble - but many may like this tuning

Picture are default 1200 x 800 resolution - click to view larger images.

FiiO have been expanding their earphone range recently, and I've been fortunate enough to be part of their journey – testing and reviewing their very early releases, and watching them mature in a very short time period. The difference with FiiO is the speed at which they've advanced, and also the quality of their products (given the very short time they've been in the earphone game). I reviewed their F9 in September, and it was a real game changer. Permanent material triple driver hybrid IEM with SE and balanced cables, and coming in at a miserly $100. The fit was superb, and the sound was excellent (barring one little obtrusive lower treble peak).

Two months later, and FiiO have now released their “Pro” version of the F9. So what has changed, and has it improved on the original? Lets put it through it's paces.


By now, most Head-Fi members should know about the FiiO Electronics Company. If you don’t, here’s a very short summary.

FiiO was first founded in 2007. Their first offerings were some extremely low cost portable amplifiers – which were sometimes critiqued by some seasoned Head-Fiers as being low budget “toys”. But FiiO has spent a lot of time with the community here, and continued to listen to their potential buyers, adopt our ideas, and grow their product range. They debuted their first DAP (the X3) in 2013, and despite some early hiccups with developing the UI, have worked with their customer base to continually develop the firmware for a better user experience. The X3 was followed by the X5, X1, X7 and most of these DAPs are now into their 2nd or even 3rd generations.

They've also developed new cables, desktop and portable amplifiers, DACs, ear-buds and earphones. FiiO’s products have followed a very simple formula since 2007 – affordable, stylish, well built, functional, measuring well, and most importantly sounding good.


The FiiO F9 Pro IEM that I’m reviewing today was provided to me gratis as a review sample. Although I have made it clear to FiiO on many occasions that I still regard any product they send me as their sole property and available for return any time at their request, they have told me that the product is mine to do with as I see fit. So I thank them for the ability to continue use of the FiiO F9 for follow up comparisons. I do not make any financial gain from this review – it is has been written simply as my way of providing feedback both to the Head-Fi community and also FiiO themselves.

I have now had the FiiO F9 Pro IEM for 3 weeks. The retail price at time of review is ~ USD 139.

PREAMBLE - 'ABOUT ME'. (or a base-line for interpreting my thoughts and bias)

I'm a 50 year old music lover. I don't say audiophile – I just love my music. Over the last couple of years, I have slowly changed from cheaper listening set-ups to my current set-up. I vary my listening from portables (mostly now from the FiiO X5iii, X7ii and iPhone SE) to my desk-top's set-up (PC > USB > iFi iDSD). My main full sized headphones at the time of writing are the Sennheiser HD800S, Sennheiser HD600 & HD630VB, MS Pro and AKG K553. Most of my portable listening is done with IEMs, and it has mainly been (for pleasure) with my own personally owned IEMs - the Jays q-Jays, Alclair Curve2 and LZ Big Dipper. A full list of the gear I have owned (past and present is listed in my Head-Fi profile).

I have very eclectic music tastes listening to a variety from classical/opera and jazz, to grunge and general rock. I listen to a lot of blues, jazz, folk music, classic rock, indie and alternative rock. I am particularly fond of female vocals. I generally tend toward cans that are relatively neutral/balanced, but I do have a fondness for clarity, and suspect I might have slight ‘treble-head’ preferences. I am not overly treble sensitive, and in the past have really enjoyed headphones like the K701, SR325i, and of course the T1 and DT880. I have a specific sensitivity to the 2-3 kHz frequency area (most humans do) but my sensitivity is particularly strong, and I tend to like a relatively flat mid-range with slight elevation in the upper-mids around this area.

I have extensively tested myself (ABX) and I find aac256 or higher to be completely transparent. I do use exclusively red-book 16/44.1 if space is not an issue. All of my music is legally purchased (mostly CD – the rest FLAC purchased on-line). I tend to be sceptical about audiophile ‘claims’, don’t generally believe in burn-in, have never heard a difference with different cables (unless it was volume or impedance related), and would rather test myself blind on perceived differences. I am not a ‘golden eared listener’. I suffer from mild tinnitus, and at 50, my hearing is less than perfect (it only extends to around 14 kHz nowadays). My usual listening level is around 65-75 dB.

For the purposes of this review - I used the FiiO F9 Pro straight from the headphone-out socket of many of my portables, but predominantly the X5iii, X3iii, X7ii and my iPhone. I did not generally further amp them (I did test them with my Q1ii, A5, and XRK NHB pocket amp ), as IMO they do not benefit greatly from additional amplification (YMMV and it may depend on your source). In the time I have spent with the FiiO F9 Pro, I have noticed no change to the overall sonic presentation (break-in). Time spent now with the F9 Pro would be approximately 25-30 hours.

This is a purely subjective review - my gear, my ears, and my experience. Please take it all with a grain of salt - especially if it does not match your own experience.

You may notice large parts of this review are similar to my F9 review – its simply because the design and much of the tests I ran are similar – so it was far easier to simply follow the last review. Some may see this as lazy – but it gives me a chance to get impressions out sooner. I followed the same meticulous testing and did not cut corners in gathering the information.


The FiiO F9 Pro arrived in an approximately 110mm x 165mm x 53mm retail box with a picture of the F9 Pro on the front cover. Its essentially the same sized box as on the F9 – but includes the “Pro” designation and reference to the Knowles dual BA driver. Inside the retail outer is a black box and lid – simply adorned with the FiiO logo.

Inside you get a black glossy Pelican case, the F9 Pro in a cut-out foam enclosure, but this time a step up in accessories. You get the two cables – one is single ended with on-cable Android controls, and the other is a very flexible balanced cable. You also get 4 sets of tips (3 different silicone and 1 set of foams), the usual manuals, and one soft carry case.

Retail boxFull package contents
The storage case is very similar to the Dunu Pelican type cases, has internal measurements of ~ 98mm x 58mm and approx 34mm deep. It is rigid with felt like internal padding and provides pretty good protection as well as storage. Because of it's size, its more suited to jacket pocket than pants pocket use.

The new pocketable soft-case is (IMO) brilliant. Its essentially a neoprene fabric clamshell (zipped) which has sufficient padding to protect, but is small enough to fit in a pants / jeans pocket. Apparently it is also water resistant. I absolutely love it.

So a step-up on the original F9 package for sure – so far, so good.

Pelican and soft caseTip Selection
(From FiiO's packaging / website)
ModelFiiO F9 Pro
Approx price$139 USD
TypeTriple Driver Hybrid
Driver DD1 x 9.2mm Titanium DD
Drivers BA1 x dual BA Knowles TWFK-30017-000
Freq Range15Hz – 40kHz
Sensitivity106 dB /mW
Cable1.2m, replaceable (MMCX) x 2
Jack3.5mm gold plated right angled
Weight21g with default cable
Casing materialAnodised CNC aluminium alloy

The graphs I use are generated using the Vibro Veritas coupler and ARTA software. Ken Ball (ALO/Campfire) graciously provided me with measurement data which I have used to recalibrate my Veritas so that it mimics an IEC 711 measurement standard (Ken uses two separate BK ear simulators, we measured the same set of IEMs, and I built my calibration curve from shared data). I do not claim that this data is 100% accurate, but it is very consistent, and is as close as I can get to the IEC 711 standard on my budget.

I do not claim that the measurements are in any way more accurate than anyone else's, but they have been proven to be consistent and I think they should be enough to give a reasonable idea of response - especially if you've followed any of my other reviews. When measuring I always use crystal foam tips (so medium bore opening) - and the reason I use them is for very consistent seal and placement depth in the coupler. I use the same amp (E11K) for all my measurements - and output is under 1 ohm.

The graphs are provided merely as a point of discussion, and later in the review I've included comparisons to other IEMs for similar reference.

My quick sonic impression of the FiiO F9 Pro – written well before I measured:
  • Bass is very linear but also has good extension, with a small mid-bass hump. There is audible sub bass rumble but it is in balance with the rest of the signature and does not overpower.
  • Lower mid-range is also reasonably linear, with a light recession. Both male and female vocals are well represented and sound quite natural. Upper mid-range is emphasised, and reaches a peak in the presence area. Female vocals have a a very good sense of euphony, and there is good cohesion and transition from lower to upper mid-range.
  • Lower treble extension is good and there is a little heat further up the lower treble, but this time it does not create the occasional harshness I got from the original F9.
  • The Pro manages to take everything which was good about the original F9 and recreate it, but this time without the occasional heat from the problematic 7 kHz spike. I later found out that it has been moved a little more into the 8-9 kHz range, and for me becomes less obtrusive.
  • Channel matching is good on the pair I have – very good in the mid-range and treble, but the dynamic drivers are slightly out (its not noticeable with music).


The FiiO F9 Pro (like the original F9) is beautifully built and seeing what FiiO can do for really does make me question how so many other companies struggle to get ergonomic design right. The main body is CNC'd, sand blasted and then anodized for a really nice metallic finish. The colour this time is a really nice titanium rather than the darker obsidian colour of the original. There is a design on the outer shells, but even that is devoid of hard edges. The entire shell is beautifully rounded and sized to perfection

The F9 measures approx 21mm across with a total height (including cable exit) of 17mm, and depth of 12mm.The nozzle is angled forward and extends approx 6mm from the main body (so relatively shallow fitting). It is 5mm in diameter with a generous lip and mesh protective cover.

External face viewFront viewInternal view
On the internal face of each unit are two ventilation ports and a L or R designator. The cable exit uses an MMCX connector and this is situated on top of the main body, and naturally forward. The connectors are tight, and although they do not sit flush with the main body, they still feel very sturdy. The other changes from the original F9 is the small red or blue marking on shell next to the MMCX socket (makes IDing left or right very easy), and also the angle of the cable exit (allowing other after-market cables to be used more easily).

The F9 Pro comes with two included cables – a standard 3.5mm stereo which has in-line mic, volume and playback controls, and also 2.5mm balanced cable option. Both cables have a hard rubber / moulded plastic housing for the MMCX connector which then joins to preformed flexible ear-hooks which are extremely comfortable and keep the IEM in place brilliantly (I love this design). On the MMCX mating collar are either red or blue markings which makes determining left or right very easy, and FiiO have also added knurling to the cable ends to make grip easier for removal. Small changes – but excellent design.

Rear viewComparison with original F9Comparison with original F9
The SE cable has a control unit on the right side which hangs just about equal with my jaw if worn cable down (so ideal height for the mic). The on-cable controls are designed to work with Android devices and do so brilliantly with FiiO's X1ii, X3iii, X5iii and X711 devices, allowing play/pause (one push), next track (two pushes), and previous track (three pushes). The volume control rocker also works. The microphone is crystal clear for calls (with my iPhone SE), as is the audio. I also tried the F9 with my wife's Galaxy, and everything worked as it should.

Below this (about mid-chest) is a small tubular y-split with good relief below the split, but no relief above it. Y splits tend to be a little more forgiving in terms of wear, so no real issues with this. The jack is gold plated, 4 pole (for the in-line controls) and right angled. It has a small shoulder which allows perfect mating to my iPhone without having to worry about the case being an issue. It also has very good strain relief. The balanced cable is a very soft and pliable twisted pair, and FiiO tells us it is silver plated OFC. There are the same formed ear-loops and this time a 2.5mm balanced jack.

ConnectorsSingle-ended cableBalanced cable
Both cables have a very “Dunu like” rubber cable tie intact with the cable – the same as that used on their other IEMs and pretty much all of Dunu's releases now. This is a really simple mechanism that is unobtrusive - but means that whenever it's time to store the IEMs, the cable is always tidily looped. This remains one of the most simple, yet practical, methods of cable ties I have ever seen.


I'll start with the easy one (isolation), and we can then look at fit and comfort. Isolation will be a little dependent on tip selection, and if you get a good seal, it is slightly above average for a hybrid with a dynamic driver. It is pretty good for most situations, but as soon as things start getting too noisy (public or air transport etc), you may find yourself wanting something with a little more isolation. The F9 Pro are designed to be worn cable up. Fit and comfort is exemplary – especially with the formed loops.

Most tips fit pretty wellAnd the F9 Pro are very comfortable
I have one ear canal slightly different to the other one (my right is very slightly smaller) - so I tend to find that usually single silicon flanges don't seal overly well. This is often even more of an issue with shallow fitting IEMs. Because the F9 Pro has a nice nozzle lip, I had no issues fitting any of my tips, and had great success with Ostry’s blue and black tuning tips, Sony Isolation tips, Spin-fits, and also Spiral Dots. The included tips were also pretty good, but I settled with what suits me best, and in the end I've been using either Sony Isolation, stretched Olives or Symbio Mandarins.

The FiiO F9 Pros sit nicely flush with my outer ear, and are extremely comfortable to lie down with. I've slept with them often, and have had no discomfort on waking. The combo of the in-line controls with a FiiO DAP makes them brilliant for late night.

So how do they sound?


The following is what I hear from the FiiO F9 Pro. YMMV – and probably will – as my tastes are likely different to yours (read the preamble I gave earlier for a baseline). Most of the testing at this point (unless otherwise stated) was done with my X7ii, no EQ, and Sony Isolation tips. I used the X7ii simply because paired they not only gave me a very transparent window to the music with low impedance, and more than enough power – but also allowed me to use the balanced option. There was no EQ engaged.

For the record – on most tracks, the volume level on the X7ii (paired with AM3a) was around 30-35 Single-Ended or 45-50/120 Balanced (on low gain) which was giving me an average SPL around 65-75 dB. Tracks used were across a variety of genres – and can be viewed in this list


  • Sub-bass – good extension, nice audible rumble, balanced with rest of spectrum and doesn't over-power.
  • Mid-bass – very slightly elevated almost like an HD600. Sounds natural and gives good impact without masking the mid-range.
  • Lower mid-range – slightly recessed compared to bass and upper treble, but not enough to make vocals distant. Male and female vocal fundamentals are really good – rich and full.
  • Upper mid-range – elevated compared to lower mid-range, and there is a very even rise from 1 kHz to the first peak at just over 2kHz. Cohesive transition from lower to upper-mids, and very good euphony for female vocals.
  • Lower treble has a nice balance throughout, and a peak at ~8-9 kHz. There is extremely good detail with this tuning, and what surprised me was the excellent way it handled both cymbal strikes and also the subsequent decay. There might be the slightest bit of heat there, but nothing I feel an overwhelming urge to EQ out (although there is very occasional sibilance present).
  • Upper treble rolls off like most headphones from about 14 kHz onward – but enough extension to provide “air”.
Resolution / Detail / Clarity
  • Clarity overall is stunning. Upper mids and lower treble have enough emphasis to give guitars bite and definition. Micro details are very evident.
  • Cymbal hits have a lot of clarity and presence but unlike the original F9, this time they are clearer without being brash or brittle, and the decay is really excellent. Brushed cymbal stokes (jazz) are also wonderful.
Sound-stage, Imaging
  • Directional queues are good without being over emphasised. Presentation of stage is mostly just on the periphery of my head space with binaural tracks, but the violin in Tundra does sit outside (nice portrayal of width).
  • Very close to circular sense of sound-staging – with very slightly more lateral L/R leaning, but the impression of depth is extremely good.
  • With the applause section of “Dante's Prayer”, the FiiO F9 Pro shows an excellent sense of immersion (the sound of the audience flowing around me), and this time the overall impression was of more realism than the original F9 delivered. “Let it Rain” is usually my next track to listen to and it gave a nice 3 dimensional feel (the way it is miked). Guitar is crisp and clear. There was the usual amount of sibilance with Amanda's vocals – and it should be there because its in the recording – and again this time the F9 Pro is making a better job of not accentuating it.
  • Overall clarity and balance of the signature.
  • Very good sense of stage and imaging
  • Really nice cohesion with lower and upper register vocals
  • Great for both female and male vocals and with enough bass warmth to stop things being too dry or sterile.
  • The 8-9 kHz accentuation may be slightly uncomfortable for some if you're not a treble lover.
  • Occasional sibilance accentuation for me – but its only just there.

The FiiO F9 Pro doesn’t need amplification for overall volume – and because its impedance isn't overly low, any source with an output impedance of less than 3 ohms should pair OK.

Great with any sourceNo extra amplification required
With my iPhone SE around 35-45% volume is more than enough with most tracks, and the FiiOs are generally at around 45-50/120. I tried the F9 Pro with the Q1ii, A5, HVA and a really nice little amp from XRK (which I’ll be reviewing soon). None of them seemed to be adding anything to my listening set-up other than some extra bulk. The A5 was really overkill, and I had to be careful to use variable line-out to get a usable volume (for my quieter listening tastes).

This was harder for me than with the original F9 – simply because I really enjoy the default signature. I added some extra sub-bass via the Q1ii's bass boost, and while the F9 Pro responded with no distortion or clipping, for my tastes it just sounded a bit woolly and warm. I also tried trimming a few dB off at 8 kHz using the X7ii's EQ. It definitely slightly smoothed the upper end, and did remove the very little sibilance I sometimes experienced. Overall I'm actually OK with the default tuning. Either way the F9 Pro seems to respond well to EQ. I'm just not sure if many people will need to utilise it.

I measured these, and there was no difference with the X7ii's AM3a amplifier module apart from volume. Even the slight change in impedance wasn't enough to change the overall frequency response. I'm not a great believer in the adage that balanced makes a huge difference. Yes, if the implementation is vastly different you can sometimes notice a difference, but more often than not the changes to cross-talk are already below the audible barrier, and most modern set-ups don't have crosstalk issues anyway. There was no difference perceptible to me once I'd volume matched. I knew I'd get questioned on it, so I utilised the Q1ii and took 2 readings – balanced and single-ended. I then volume matched (exactly a 6 dB difference), and what do you know – no frequency change. Its nice to have the option – but sonically I don't hear any benefits. If you volume match properly, I doubt you will either.


These comparisons were all done with the X7ii, (no EQ) – and volume matched using a calibrated SPL meter and fixed 1kHz test tone first. Because I already knew how good the F9 Pro sounded to me, I wanted to throw it up against the best in its price bracket. So I chose the F9 original, Simgot EN700 Pro, Brainwavz B400 and my benchmark – the Alclair Curve.

FiiO F9 Pro (~USD 139) vs FiiO F9 Original (~USD 99)

FiiO F9 Pro and FiiO F9Comparative frequency response
We can make this one pretty short. As far as build and design goes, they are practically identical – size material etc. The cosmetic changes introduced on the Pro are pretty good – knurling on the cable socket housing, colour coding for L/R, different angle on the cable exit (friendlier to after-market cables), and of course the Pro has the very good carry pouch and also the extra tip selection. Both have similar isolation (reasonable for a hybrid) and both are extremely comfortable.

Of course the real difference is with the change of BA dual driver (F9 Pro utilises a Knowles dual BA set-up). As you'll see from the graph, the bass remains identical, and the tuning is practically the same except for the Pro having just a touch more upper midrange, and the lower treble peak being pushed back a little. The sound is very, very similar – with the F9 Pro having a subtly more engaging mid-range, and a little less troubling lower treble peak. The interesting test for me was using a splitter, and listening to the left ear-piece of the F9 original with right ear-piece of the F9 Pro. The differences were noticeable for about the first 30 seconds, and then as my ears adjusted, I may as well have been listening to a single stereo pair.

Is the upgrade worth it? For the extra accessories, the minor design changes, and the subtle changes to sound – I think it is. But don't expect a big change. If I had the original F9 and was happy with it, I'd probably pass on the Pro. But if you're looking to get a little closer to perfection on a budget, the F9 Pro is definitely on my recommended list!

FiiO F9 Pro (~USD 139) vs Simgot EN700 Pro (~USD 150)

FiiO F9 Pro and Simgot EN700 ProComparative frequency response
The EN700 Pro from Simgot Audio is one of my favourite IEM's in the sub $150 bracket. It hasn't been out that long – but it is an incredible example of how far the industry has come in the last few years.

Both the F9 Pro and EN700 Pro have extremely ergonomic builds, solid builds and quality cables. With the F9 Pro you get the extra balanced cable, but with the EN700 Pro you get slightly better quality on the SE cable (along with 2 pin connectors which I prefer). Both have great design, good accessories, and reasonable isolation. More importantly both are incredibly comfortable to wear.

Sonically they are very similar in the bass although the EN700 Pro may have just a little more warmth. Both have excellent mid-ranges, and the real difference in the mid-range is the lower treble – where the F9 Pro is a little cooler and brighter. The EN700 Pro is warmer and smoother in comparison.

This one for me is a tie, and really comes down to individual preference.

FiiO F9 Pro (~USD 139) vs Brainwavz B400 (~USD 180-220)

FiiO F9 Pro and Brainwavz B400Comparative frequency response
Brainwavz came from nowhere with the B400, and knocked it out of the park IMO. A quad BA in a very ergonomic housing, and spectacular tuning. Compared to the F9 Pro, I'd call design and ergonomics a tie, the F9 Pro pulls slightly ahead with the more permanent materials and overall finish quality. But we are splitting hairs here – both are truly well designed, well built, and extremely comfortable monitors.

The difference here is in the tuning, with the B400 opting for a much flatter overall signature with a smoother upper end – whilst still retaining very good extension. Both are exceptionally clear and clean sounding. Because the B400 has less lower treble and upper-mid emphasis, it has the tendency to sound a little warmer overall, with the F9 Pro again sounding cooler and brighter. The interesting thing is the bass though. I love the B400's speed, but there is something alluring about a well tuned dynamic driver, and the F9 Pro somehow manages to get this absolutely spot on in comparison. Again – both are exceptional monitors and will come down to preference. I might lean slightly toward the F9 Pro in this comparison – but simply because of my own preference for a slightly brighter and cooler monitor.

FiiO F9 Pro (~USD 139) vs Alclair Curve (~USD 249)

FiiO F9 Pro and Alclair CurveComparative frequency response
I know this is getting a little out of the F9 Pro's depth, but what happens when I put it against one of my favourites in the sub $250 bracket? The Alclair Curve is the most ergonomic IEM I own (and yes this one I do own). Both IEMs have fantastic build quality – with the F9 Pro's shell being alloy vs the plastic/acrylic shell of the Curve. Both have replaceable cables. Both have exceptional comfort. The F9 Pro of course has the balanced cable option – the Curve isolates much better.

Sonically these two have similar overall signatures. Linear well extended bass, nice balance overall, a bump in the mid-range, peaks in the lower treble. The main difference is that the Curve has a flatter overall signature, where the F9 Pro is more coloured (especially in the upper mids and lower treble). The F9 Pro is not embarrassed at all in this company. For me personally – I'd still pay the extra and take the Curve for most music, but there is definitely some tracks (especially acoustic guitar with vocals) where the F9 Pro's coloured mid-range simply shines. The F9 shows incredible value for money – and that’s why I chose this particular comparison.


By now you'll already know where I see the strengths of the F9 Pro like the original F9, the one massive strength is in perceived value. With the F9 Pro its simply off the charts. This is an IEM which can comfortably go toe to toe with IEMs at much higher prices. While it doesn't necessarily set a new bench-mark in quality/price ratio, it comfortably lives alongside the best in its price bracket (and in the bracket above it).

If these were on the market when I was originally looking to buy a higher end pair of IEMs (I eventually started with the Shure SE425 and later the SE535), I doubt I would have spent the money I did. For a budget set-up (which doesn't sound budget), I can't think of too many which would beat it.


FiiO has really pulled out some surprises with their IEM releases this year and the tweaks in the F9 Pro show the maturity FiiO is already reaching – even as a comparative newcomer to IEMs. The F9 Pro is a serious contender at a low price (almost entry point for some).

It combines good build and design, great ergonomics, and well thought out accessories, with an exceptionally mature and balanced signature. If you're sensitive to treble (especially at 8-9 kHz), or dislike a cooler brighter overall signature, then it may not be for you. But if like me you appreciate overall balance, with a mid-forward signature, and a cool clean and detailed presentation, you are in for a real treat. If you prefer the signature, but find it a little overdone, a drop on the 8 kHz EQ slider of about -3 dB is a really quick fix.

I put these through my new objective ranking calculation module, and unsurprisingly they scored incredibly well. I would unreservedly recommend the F9 Pro. In this price range, its going to be hard to beat.

Scoring Chart
HeadphonesFiiO F9 Pro (out of 10)
My ScoreOut Of WeightingWeighted Score
Sound Quality
Bass Quality8.5108.00%0.68
Mid-range Quality8.5108.00%0.68
Treble Quality8108.00%0.64
Overall Tonality8.5108.00%0.68

I have read many of your excellent reviews, and wanted to get your opinion on the F9 Pro as it compares to the Campfire Orion. I had the F9 SE but they were confiscated by a family member (with my blessing). I enjoyed them, and needing a replacement, began looking at available options. I saw your previous review of the Campfire Orion, and as it is one of the IEM's I am considering, hoped you might be able to provide some comments comparing the two IEM's; price differential aside. Thanks.
I'll send you a PM with the graphs. Orion is flatter, and leaner. F9 Pro has more bass impact, more mid-range emphasis, and more treble - overall it is more vivid, where the Orion is more balanced. Comfort wise - the F9 Pro is more ergonomic, and both fits better and is more comfortable (for me anyway)