FIIO FA9 REVIEW: Smooth naturalness with mature neutral tuning


SOUND: 8/10
VALUE: 7.5/10

THE PLUS: Smooth tonality with a nuanced macro-resolution, Neutral yet musical, Clean Bass-mids-treble, beautiful vocal, non-fatiguing treble, tunable switch make it versatile, generous accessories and nice packaging
THE SO-SO: Not very exciting to listen too, not as crisp as we could expect, lack of separation between sub and mid-bass, timbre lack a bit of texture, a rather intimate soundstage

FIIO often collaborates with Knowles balanced armature drivers company, in fact, it looks like all their IEM that use balanced armature are from Knowles.

From the single customized BA used for FIIO FA1 to the FH7 Hybrid flagship using 4BA, they earn lot of valuable experience implementing different balanced armature models from this great American micro acoustic company.

In my audiophile journey, I have tried multiple IEM using Knowles BA, should it be multi BA from less known companies like Audiosense and Akoustyx or Hybrid iem like IKKO OH10, DUNU DK2001, and FIIO FH7, I’ve always been please by the natural timbre of Knowles drivers. I tend to prefer their BA over cheaper Chinese BA like Bellsing and even older Final Audio BA used in F series which can sound thinner, brighter, or  more artificial.

In the other hand, when badly implemented, the Knowles BA can sound overly smooth and lack in the attack, this is mostly due to distance placement from nozzle end as well as multiple filters and dampers used. Knowles permit to tune the sound with different filter material, some will overly affect attack sharpness. Some models are brighter than others too, and my theory is that it’s because they are of a lower quality like the 33518 model.

My favorite multi-BA IEM is the Audiosense T800 that uses 8 Knowles balanced armature, so when I was aware FIIO was launching a flagship 6BA universal custom in-ear, my curiosity was extremely high as well as my expectation. I know that the mids and highs would most probably be great, but my worry was about bass even if FIIO uses an ultra-long sound tube that promises excellent bass performance. From the specs sheet, no Knowles BA drivers can go lower than 200hz, but the Audiosense T800 uses the exact same 31618 bass dual woofer driver and achieve a very authoritative bass performance with a chunky impactful slam. I was really surprised to hear a completely different low end with the FA9, with a leaner and more natural extension, but the less weighty impact and forward presence. Those two IEM aren’t similar at all, the T800 being more V shape while the FA9 being more neutral and balanced.

One of the FIIO FA9 highlights is its sound switch, which is a novelty in the FIIO IEM line up. This ”new” way of tuning your IEM to your liking was the most intriguing feature for me and I will share more thought about this in this review, but the switch combination permit you to have 8 different sound flavors.

Priced 500$, the FA9 enter a very competitive price range where I became more severe to judge the benefits return it gives. The sound switch sure is a plus in terms of investment value, but it means nothing if the overall tonality and technicalities aren’t impressive. Let’s see in this review if the FA9 should be seen as an End Game Flagship IEM or more like an audiophile IEM collector caprice.

The FIIO FA9 can be bought for 499$USD on their official Aliexpress STORE.

Type: In-ear
Acoustic Principle: Closed
Drivers: 6x Knowles Balanced Armatures
Impedance: 16-32Ω @ 1kHz
Frequency Response: 15Hz – 40kHz
Sensitivity: 111 dB/mW
Cable: 1.2m interchangable 3,5mm MMCX cable
Connector: 3.5mm


FiiO FA9 - 6 Knowles BA IEM w/3 sound adjustment switche ...

The FA9 use 6 Knowles BA, or more likely high-end dual BA. The SWFK-31736 dual tweeter BA is used for treble, the EJ-33877 for mid-range, and the dual woofer HODVTEC-31618 for low frequencies. These are flagship balanced armature that are very costly, for example, the 31736 sells between 70$ to about 40$ when bought in high quantity. Another particularity of FA9 acoustic engineering is the inner tube design that are connected to BA and acts like passive tuning, these earphones use the longest tube ever done for connecting the bass BA to the nozzle end, at 80.6mm of length it’s very puzzling to wonder how they do to fit it in rather small housing of FA9, it permits to avoid interference with other BA and condense the bass so it became amplify and more powerful. As well, it uses a 4-way crossover that can be tweak via the 3 tuning switch by changing different crossover paths affecting different frequencies response zone.


When you present your product as flagship, it should have an impressive presentation with great care to details so the full purchase experience feels respectful towards the consumer reception. FIIO sure gives a lot of effort to achieve a luxurious product experience and the whole unboxing process shows it well. FA9 boxing is classy, sober, and practical. It comes in a glossy black big box that has a distinctive look. When opened, the shinny IEM are beautifully presented and star of the show. When you pull off the first package cover, the presentation is again well done with a very informative ear tips display (and holder) that have nothing less than 14 different pairs of ear tips, including real Spinfit, bi-fangle, silicone and memory foam with description under it like Vocal, Balanced, Bass so you know how it will affect the sound, this is a very welcome display! The included carrying case is very fancy too, made of real leather and with enough space in it to include an extra cable or another IEM or…well, another carrying case as included with the FA9. Yep, the number of accessories is near over-kill, but I would have preferred an extra balanced cable or modular cable than an extra carrying case.  Anyway, we are already very spoiled with FA9 accessories.


The FA9 uses a medical-grade resin plastic of very high quality, which is smooth and easy for the ears. They are of medium size for a multi-BA scoring that many drivers and will fit any ears. The housing share is long and thick with an organic shape that is well-conceived for a universal custom in-ear. The IEM is quite light due to both housing and drivers’ low weight. Unlike some other UIEM, the nozzle length is both enough long and small in circumference so you don’t have issues finding the right ear tips. Connectors are solidly embedded into the shell without any asperity that can create easy disconnection. The switch system is perhaps the only fragile part even if well built because I feel it’s where water damage can occur if you walk under the rain or sweat a lot, as well, as you need a tool to use them it can perhaps cause scratching to the body, but thanks to high-quality resin, it’s not easy to scratch at all.


CABLE is the very same LC-3.5C model included with the FH7, it’s of very nice quality, thick and flexible, beautiful, and with solid mmcx and all-metal L shape jack. It really feels tolt, but as I feel the FA9 benefit from the balanced output, it would have been incredible to have the FIIO modular cable included, even if it makes the price 50$ more.

DESIGN is not revolutionary and uses a common shell that is very similar to the Audiosense T800 or whole FIIO FA series, still, this kind of housing is among my favorite due to good isolation, comfort, and durability. The FA9 is strictly thought to be used with cable over-ear, even with a cable that has no ear hook it does not tend to fall from ears do to an enough deep fit. The molded organic shape of the housing is well thought and does not have any protuberance that can feel uncomfortable or too invasive in the ears.

ISOLATION is above average and you don’t need to crank your music at high volume to enjoy noise-free listen. Noise leakage is extremely minimal and among the best in its class. Unlike Dynamic drivers, the BA tends to project sound forward without background reverberation and helps to avoid high noise leakage.



It’s not clear if the GAIN switch just affects impedance or sensitivity too, anyway from the specs it’s 16ohm when ON and 32ohm when off, both surely with rather high 111db of sensitivity. I found the FA9 to sound more open and lively when using 32ohm impedance with a powerful DAP, while it’s brighter-shoutier at low impedance. Drove with JDS LAB ATOM amp can produce slight bass distortion at very high volume but sound edgier in attack and weightier in bass slam with the more holographic soundstage. The FA9 is very sensible to the audio pairing you make, powerful clean DAP with slightly bumped bass can do a good match as I can conclude using the Ibasso DX90 which add extra bass and sparkle.


The sound switch system is what makes the FA9 special and FIIO state you can have 8 different sounds signature by tweaking the crossover via the switches. Did it mean it’s like owning 8 different IEM? Not really because overall tonality, technicalities and timbre stay the same, it’s just about little boosting or taming of certain frequencies range here.

Switch 1 ON=lower impedance and louder sound. Brighter tonality and slightly more aggressive attack. Less clean and little more grainy than with higher impedance.

Switch 1 OFF= Impedance is now 32ohm instead of 16ohm. Sound is more clean, organic and nuanced with fluid transparency. No harshness to be found.

Switch 2 ON (S1+S3 OFF)= Slightly more V shape sound with extra bass and treble, mids are still clean but less dynamic and lively.

Switch 2 and 3 ON (S1 OFF)= More analytical sound with fowards mids and extra upper treble boost that enlight mico-details and percussions.

Switch 3 ON (S1+S2 OFF)= Bass is leaner but still clear and articulate, mids are more present and lush and treble is well balanced.

Switch 2 and 3 OFF (S1OFF)= Warmer signature with biggest bass focus , relaxed mids and treble.



While the sound switch system does tweak the sound a little, I feel ear tips are even more influential. The switch cannot improve soundstage, imaging, or bass impact but the ear tips can so I suggest you try as much as you can and stick with the one opening the more the sound. For me, the BASS tips is the best and it opens the sound and permits the bass to be better articulated. The Spinfit is nice for extra punch and energy but makes soundstage a little tunnel-like. Everybody has different ears canal shape, so I’ll just say that it looks like the FA9 like to have ear tips with a big nozzle hole but not too long length.



Gear used: Xduoo X20 (balanced and unbalanced), Ibasso DX90, X20+JDS LAB Atom, Xduoo X3, Tempotec V1+Audirect Beam2 (favorite pairing is with Ibasso DX90)

It’s always a little complicate to review an IEM with multiple tuning possibilities, should it be with changeable nozzle filter or tuning switch, you just can’t make a different in-deep sound review of every tuning tweak because it will be very redundant in numerous aspects like timbre and overall tonality. Firstly, let’s be realist, you do not get 8 different IEM with the FA9, while the switch do boost or lower certain frequencies range, it’s no drastic change but more taming or not a certain part of the sound. Firstly, has a purist, I tend to want the less compromise sound and I found that putting all the switch off offer the more open, clean and detailed sound. FIIO states it ”boost” bass or treble when On and could tame the bass but the difference is very minimal, you still have impressive bass extension whatever tuning switch you play with.
So, OVERALL TONALITY is lean, warmish and smooth with a hint of lower bass emphasis, clear full mids and liquid delicate treble. Tough with high sensitivity the sound can be a little brighter, it’s never rough or aggressive, the bass extension for BA is very well controlled and quite realist, and perhaps among the more natural one I heard in muli-BA whatever price range, but it’s not particularly impactful in mid-bass punch but very thigh in control. The mids are very present and well separated, offering clear vocal with a soft edge to it. Treble is very crisp and super well controlled. Tonal balance is excellent, all BA working in fluid tandem and never feeling dissected, it reminds me a little the impressive transient response of a full beryllium high-end IEM like the Final Audio A8000, but tamed in impact and less detailed in texture. Timbre will never aggress you with unwanted grain or fuzzy density, it’s natural yet very polished. Transparency is another impressive aspect of FA9, it permits to have good articulation and separation as well as a good sense of deepness. In fewer words, the FA9 offer an organic clean sound that fully cover all frequencies range without really coloring the sound apart from little bass and treble bump when you listen to them for the first time you aren’t hit with any particular emphasis but rather slowly immerse into a fascinating life-like sound experience. It really feels like FIIO tries to tune the FA9 to please everybody (or offend nobody) and put the tuning switch to be sure bass and treble lover can have extra enjoyment, so it’s not a bright or warm IEM but a Lukewarm one.


TONALITY is near neutral with natural extension in low and mids and slightly sharper presence in the treble. The sound is smooth and warm until mid and high treble which adds a hint of brightness that mixes organically with the sound spectrum, not unbalancing tonal fluidity by extracting too much texture details in the upper register. Smooth, effortless, balanced and liquid in transient response, you feel in life-like musicality with extra comfort due to a soft sound pressure edge (in high sensitivity it’s a hint more shouty-brightly).

TIMBRE has great transparency, a nuanced and subtle texture and a nice sense of 3D density that do not have the disadvantage of opaque thickness. It’s polished without sounding tamed or blanked. I rarely heard this kind of timbre, apart from real life and my brain is really tricked here!

SOUNDSTAGE has average wideness that permits music to feel just enough out of your ears. Don’t get me wrong, it’s wide enough, but not very tall and slightly deeper than all the rest so you have a rather intimate presentation in the end.  It’s important to note that ear tips fit will greatly impact on spatiality result (you can read more about this in eartips section).

BASS is very unique and like nothing I ever heard before, I think this will be a love or hate affair due to its dense smoothness and soft impact. We have very good articulation with a longer resonance that tends to thicken the sub line without affecting overall resolution, the extension is a little wobbly and not as natural as the end of bass impact found with a dynamic driver, it sounds more similar to the bass presentation of planar IEM or Headphones than a balanced armature too. Still, as said, the Audiosense T800 use very same dual woofer driver and have a more impactful and weighty slam that is nearer to DD driver than BA, while I do understand the use of a sound tube to keep bass separated from other sound spectra, I feel the long tube travel do darken both it’s texture and impact lead. It’s the type of bass that is kept in the back, mid-bass hit is not very punchy and forwards and kick can even be subdued in music mix because of sub boost, so I would not consider the bass perfectly balanced. Still, it’s far from being a flat anemic bass and the punch can become quite heavy when asked for like with the boosted kick in Trap Rap or electronic, so while the weight can be there, it’s just not very snappy with kick definition. As said, the texture is soft, so for slap bass or acoustic bass lover this can be a little underwhelming in resolution, add the compressed extension to this and your favorite bass line might sound little hollow and even undercooked. FA9 bass does better with pop, electronic, classical and some rap than jazz, rock. It’s not the fastest bass even if it’s super well-controlled and extremely clean, in term of speed, impact and even textures the Dynamic driver used in FH7 do better. To some extend, FA9 is unpredictable and finding myself banging on ”BB” from SHYGIRL is a great example of how the sub-bass can gain authority when needed, it’s presence with the digital bass instrument is pretty intense and feel like having a sub stock in the back of your head, all this without affecting vocal crispness and melody line clarity.

MIDS are gently forwards, superbly clean and transparent, smooth in timbre and have a very realist tonality. To my ears, they are the highlight of FA9, while the resolution is high, it’s never harsh or bright and it has an effortless naturalness to them. They aren’t particularly thick, but far from thin too due to a lush airiness to them that make them well extracted from rest of music. Sure, some will lack the fluid bass foundation that offers chunky male vocal gauge, but you will at least be able to understand every lyric word with high intelligibility. The instrument like violin and saxophone sound tonally right and have a wide airy presence while piano lacks a bit of weight in note impact, but this isn’t surprising as I found BA to struggle with any instrument that has sound produced by a hit, should it be an acoustic piano hammer or drum kick that need well-rounded bass and lower mids transient response for proper weight impression or percussions that need post-impact sparkle. Timbre is a hint liquid and polished in upper mids so you got a high level of clarity that is very polite. I will repeat myself here that the bass doesn’t interfere at all with mid-range so it’s always ultra-crisp and what impress is how this sharp presence isn’t offensive and keep a mellow lushness, offering sweet vocal without lipsy texture or awkward sibilance. Every instrument benefit of this clarity and while the soundstage isn’t the biggest, the FA9 will never struggle to deal with busy tracks.

TREBLE is the sound frequencies part that can be the more tweaked with FA9, should it be by using low impedance mode, different ear tips, or treble boost. It follows the same tonal smoothening that offer an organic feel to the sound but it’s the most energic aspect of FA9 musicality nonetheless. One would think that due to multi BA use the FA would sound very detailed and even analytical, but it isn’t the case at all, it’s more about macro-resolution than micro-resolution here and you will not hear a tremendous amount of micro-details pushed forwards. Instead, we have well-layered transparency, full highs presentation that offers nuanced timbre and nice extra shimmer in upper highs that offer a full extension to percussion, harpsichord or violin. The attack is quite fast and snappy without feeling super edgy or aggressive. The FA9 delivers impressively thigh and realist percussions and drum rolling that will sure make smiling jazz lovers. Sure, with Boosted Highs switch ON, the tone of highs are brighter and more forward, but it’s never to the point of creating unbalance and feel rather flat as a whole, only very few time I heard upper highs resonance that was a little trebly. It’s not the kind of highs I would call sparkly as their not a lot of decay to them, so it lacks a bit of air to permit a better articulate definition. I think FIIO targets a specific house sound that can please everyone due to the inoffensive dynamic it offers, the whole sound feels relaxed yet the treble is full and revealing. Clarity is not forced, and as a listener, you feel comfortable for a long listen free of any fatigue. The FA9 deal easily with Classical Symphony, without omitting any instrument, it offers a fluid presentation with effortless macro-resolution.

BASS: 7/10 7.5/10
MIDS: 8/10 8.5/10
TREBLE: 8.5/10 8/10
ATTACK-DECAY: 7/10 8/10



VS FIIO FH7 (450$)

The FH7 is flagship hybrid earphones from FIIO, it has an all-metal construction and it’s bigger and heavier than FA9, making it a bit less comfortable. Like the FA9, it’s tuneable, but by changing nozzle filters instead of using a switch.

SOUNDSTAGE is more intimate in both wideness and deepness with FA9, the IMAGING has better transparency and layering but instrument separation isn’t as wide and easy to spot than FH7. BASS is lighter, slightly faster, and a hint more textured, mid-bass isn’t as punchy and weighty and lower extension lack naturalness and fullness of FH7. MIDS are slightly more forwards, but more intimate too, they are smoother, thinner and airier, not as edgy and full as the FH7 which have more upper mids presence bite. The TREBLE is more delicate and transparent, it will please the treble sensitive people but I personally prefer the more dynamic highs of FH7.

All in all, the FA9 offers a flatter and even more neutral sound than FH7, making them nearer to a softened Diffuse field target while the FH7 is nearer to brighten up Harman target. It’s less fun, smoother, and more mature sounding IEM than FH7.


The Fidelity is a high-end dynamic earphone, the construction is great but the fit is less comfortable than FA9. The cable is a little cumbersome and thick but has a changeable jack so you can use both 2.5mm balanced and 3.5mm unbalanced connection. This is something I regret about FA9, because FIIO do have a modular cable with changeable jack but didn’t include it with their flagship IEM. Anyway, all in all, both construction, comfort, and accessories are better with FA9.

SOUNDSTAGE is notably bigger in all aspects with the Fidelity and the IMAGING is more spacious because of this, offering wider space between instrument but not as much layering nuance as the FA9. BASS is more textured, flatter and thinner with the Fidelity, but it has a more aggressive tonality too that makes kick hit clearer, though with less weight. MIDS are brighter and thinner with the Fidelity and has more upper mids emphasis so while it can give extra attack grip to violin, the vocal sound less full and natural than FA9. Separation isn’t as good as FA9 too and the Fidelity will struggle more with a very busy track. TREBLE is sharper and more forwards with Fidelity, it offers hint more sparkle-decay but isn’t as thick and balanced as the FA9, the attack is less fast as the FA9 which is more problematic for complex percussions that can sound a bit hot with the Fidelity.

The DITA FIDELITY offers a more bright and energic tonality with more out-of-your-head soundstage but isn’t as well balanced and full sounding as the more laid back sounding FA9.

VS AUDIOSENSE T800 (300$):

The T800 is a multi-BA using 8 Knowles balanced armature that include some used in the FA9 like the dual woofer BA for bass (without the long sound tube). The construction is extremely similar, using the same resin plastic but a bigger housing. Due to the big size and a rather small nozzle length, the T800 is less comfortable than FA9 due to the tricky seal issue that affects the sound. In terms of accessories, I personally prefer the 8cores copper litz cable included with T800 even if construction doesn’t feel as durable, as a whole, again, FIIO is unbeatable for packaging and accessories.

SOUNDSTAGE is bigger and more holographic with T800, but not as deep. IMAGING is more lively and surrounding and have wider instrument separation but not as much transparency in layering capabilities. BASS is notably more boosted with T800, it has more slam and weight and will even please basshead while the FA9 is more controlled and well separated but lack a bit of punch. MIDS are less well balanced and neutral with T800, they are pushed forwards with the help of upper mids emphasis which makes them more lively but less natural and smooth than FA9, still, they have more texture and energic attack too, as well, male vocal are thicker. TREBLE isn’t as full and balanced as FA9, making the T800 strangely W shape compared to flatter FA9, the attack is more aggressive and micro-details are pushed more forwards too in upper high which can be problematic for treble sensitive people, the FA9 has a more natural treble that does not color as much the sound.

All in all, while I still find the T800 more fun, immersive and energic, I can still conclude that FA9 is technically superior in every aspect but soundstage here. The problem is that T800 wake you up while the FA9 can make you sleep.



FIIO really impress me this time with how maturely tuned is their FA9 IEM, it isn’t an easy task to offer such a well-balanced sound using that many drivers and the tonal cohesion are very fluid. I admire the new acoustic design and the use of a super long sound tube for the dual woofer BA sure worth my respect. I see the FA9 like a laboratory for new future tunings experiment that opens new doors for balanced armature sound projection. While the sound switch did not turn as useful as I thought due to overly subtle change in sound signature, I respect the effort and think it could be quite a plus for those enamored with the overall tonality of FA9.

For 500$, the FIIO FA9 offers a well-built universal custom that is very comfortable and has high passive noise isolation, incredible packaging with a lot of accessories and ear tips and a smooth neutral sound that is perfect for a long listening session. The FA9 isn’t a fun sounding iem and even if the bass dig deep it isn’t for basshead at all, it’s neither for the treble head, but perhaps more interesting for serious mids lover that search life-like vocal and instrument in this range. The resolution is high without sounding analytical or cold, it’s calm and limpid like a beautiful lake on sunset with water that is perfectly lukewarm for a relaxing and contemplative musical immersion.

For those who like serenely lush neutrality and enjoy IEM like Final Audio E4000 or wish that Final Audio B3 sound smoother, I think the FA9 can be an interesting step up to for even better macro-resolution and cleaner mids. While the FA9 isn’t a giant killer in terms of value, it offers a sound that became tastier and tastier with time, like a fine wine full of nuance to be discovered by the mature audiophile gourmet.


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