FiiO F9 Pro Hybrid Triple Driver IEM

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  1. ryanjsoo
    "Fiio F9 Pro Review - Pure Clarity"
    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.

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    tarhana and Brooko like this.
  2. Brooko
    "FiiO F9 Pro - Excellence On A Budget"
    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.

    [​IMG] [​IMG]
    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.

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    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.

    [​IMG] [​IMG] [​IMG]
    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.

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    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.

    [​IMG] [​IMG] [​IMG]
    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.

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    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.

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    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)

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    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)

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    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)

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    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)

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    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

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