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Sony IER-M9 In-ear Monitor Headphones

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    5x Balanced Armature (BA) units for optimal sound design

    For clean high notes, rhythm, pitch and the pure emotion behind every nuanced performance, the IER-M9 has 5x Balanced Armature (BA) Driver Units, including a Magnesium alloy super tweeter.

    Sony's original design Balanced Armature (BA) Driver units 
    The unique T-shaped Balanced Armature directly drives the diaphragm for a more linear motion and clean, faithful high notes.

    Magnesium alloy super tweeter
    The IER-M9 super tweeter diaphragm is made of light weight and rigid Magnesium alloy to deliver the responsiveness required for describing subtle music nuance. The unique BA unit design also benefits from extremely low resonance thanks to a high internal loss. Internal wiring is also upgraded, with a new silver coated copper voice coil and gold-plated terminals, to faithfully reproduce sound without sacrificing even micro signals – so pitch, harmonics, and emotion are portrayed.

    Optimised sound path
    While standard BA in-ear monitors rely on a long and narrow flexible tube in their sound path, the BA drivers in the IER-M9 In-ear monitors use a wide and short sound path made of magnesium alloy. This reduces frequency peaks and dips, and gives the ideal frequency response to ensure a monitor sound you can rely on for critical listening accuracy.

    Integrated Magnesium alloy inner housing
    The BA units are held firmly in an integrated, high-rigidity housing. This helps to eliminate vibration and keeps sound clear and clean without losing even a micro nuance of sound.

    Light, durable Magnesium outer housing
    Own the stage and the moment with the light, durable Magnesium alloy outer housing of the IER-M9 In-ear headphones. Stably fit and durable against knocks or accidents.

    Audio grade film capacitor for less distortion
    Sony’s custom audio grade film capacitor in the cross-over circuit delivers much lower distortion. The audio grade capacitor of the IER-M9 In-ear headphones delivers fine, relaxed sound. Plus, audio grade solder also helps minimise any loss in signal path.

    Natural silk thread and non-magnetic undercoat plug
    The IER-M9 uses natural silk thread as a cable insulator. This natural fibre works as an absorber against vibration and prevents rustling or bumping noises when you touch the cord. The gold plating of the plug has a non-magnetic undercoat which transfers the signal preserving subtle nuances.

    Silver-coated OFC
    Silver-coated oxygen-free copper cables minimise resistance and signal-transmission loss. The result is less sound degradation, finer detail and smoother treble sounds.

    Balanced connection available
    The IER-M9 In-ear monitors come with a 4.4mm standard balanced connection cable which separates left and right sound signals completely, unlike conventional headphone cables where both channels share a ground wire. This minimises cross-talk and the resulting sound deterioration.

    Detachable cable
    The cable is fully detachable so you can replace it if needed, or fine tune your monitor sound through a different cable.

    Pre-formed ear hanger for ease and stability
    The IER-M9 In-ear headphones stably fit your ears through the universally shaped ear hanger. With firm fit and optimal housing shape, each ear bud stays in the right position.

    13 variation of ear buds
    Our earbuds come in thirteen variations – six triple comfort and seven hybrid silicon. So you can find a snug fit for all kinds of ear shape. Combining hard silicone rubber and specially-developed formed silicone, they perfectly match sound with stability and are comfortable to wear for long lengths of time.

    WEIGHT Approx. 11.0g
    General Features
    HEADPHONE TYPE Closed, Penta Balanced Armature

    DRIVER UNIT Penta Balanced Armature

    IMPEDANCE (OHM) 20ohms(at 1kHz)



    CORD TYPE Y-type

    Approx. 1.2m, silver-coated OFC strands, ear hanger, L-shaped non-magnetic gold-plated stereo mini plug, Approx. 1.2m, silver-coated OFC strands, ear hanger, L-shaped non-magnetic gold-plated balanced standard plug

    L-shaped non-magnetic gold-plated stereo mini plug, L-shaped non-magnetic gold-plated balanced standard plug
    What's In The Box
    • Triple Comfort ear buds:SS,S,MS,M,ML,L, Hybrid Silicone ear buds:SS,S,MS,M,ML,L,LL ClipCarrying case, Cable holder, Cleaning cloth, Cable clip

Recent Reviews

  1. Kygreying
    Sony IER-M9 Review
    Written by Kygreying
    Published Oct 10, 2018
    Pros - Superb imaging, clarity, details
    Strong bass (for a BA)
    Great for the price point
    Cons - Cable hanger is stiff
    Some may think bass is too strong
    In August 2018, Sony announced 3 new IEMs: the IER-M7, IER-M9, and the IER-Z1R. The IER-M7 is 4BA, retailing at S$799, the IER-M7 is 5BA, retailing at S$1,599, and the IER-Z1R is a hybrid – 2DD 1 BA retailing at S$2,299. While I’ve listened to all three, this review will be primarily focused on the M9. I’ve spent around a week or so listening to them extensively on different sources, and will explain further later on.

    Drivers and Specifications
    The IER-M9 is a “closed, penta balanced armature” IEM. Here are the technical specifications:
    Driver Unit: 5 BA, Magnesium Alloy Super Tweeter
    Impedance: 20ohms(at 1kHz)
    Frequency Response: 5Hz-4000Hz
    Weight: 11g
    Sensitivity: 103dB/mW

    I feel a need to briefly mention that these are not easily driven – quite a bit of power is needed.

    Packaging & Accessories

    The IER-M9 comes in a not-so-small package, including 6 pairs of Triple-Comfort earbuds(L to SS), 7 pairs of Hybrid silicon rubber earbuds (from LL to SS), a cleaning cloth, a 4.4mm balanced cable, a 3.5mm cable, a carrying case and of course the IEMs themselves. These are packaged and presented very well. The carrying case is fashionable, but not something that I would bring around everywhere.

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    Build Quality and Comfort

    The IER-M9 is encased in a light but durable outer casing of a magnesium alloy with a carbon fibre plate – a nice touch. The IEM itself features a pre-formed ear hanger with very strong memory, something that may appeal to some but not to others – I found that the hanger was a little bit large for my ears, but not something that would cause discomfort by any means. The MMCX connector is slightly recessed, meaning that you would not be able to attach any other cables unless you have the proprietary connector. The M9 sits snugly in my ears, although there are times that I have felt that it is a touch too big – again nothing to write home about. The isolation and fit is also great, it forms a very good seal to my ears.

    With the M7 and M9, Sony has really stepped up its game in the design and comfort categories – in comparison with the MDR-EX1000 and the XBA-Z5, the M7 and M9 look and feel amazing - no more of that odd protruding bits in your ear.


    As stated above, the M9 comes with 2 MMCX cable options, terminating in 3.5mm and 4.4mm balanced. The cables are almost identical apart from the termination and are silver-coated oxygen-free copper cables. The plug is an L-shaped non-magnetic gold-plated stereo plug. I find the cables to be of fairly high quality, they are long and rather sturdy, yet not too heavy. That said, the Y-split and the splitter above could be potentially larger. The M9 is designed to be worn over ear, and there is little to no microphonics at all when moving around with the cable. There is just a small worry that the wire is sheathed in a rubbery material that is just slightly sticky out of the box – hopefully this will not be exacerbated by heat and humidity.


    Before I begin on this section, let me attempt to provide some context – my audio journey has been as such – Vsonic GR07 à Etymotic ER4XR and Massdrop Plus à IER-M9. I’ve spent a lot of time over the past week listening to these gems. Along the way, I’ve listened to a good many of the more highly-rated options on the market, and will be using some of them as select comparisons in this review: Sony MDR-EX1000 (coming soon), Hyla CE-5 and Campfire Audio Andromeda. I find these two IEMs to be the closest in terms of comparison.

    Listening preferences – My listening consists primarily of Classical music, both of chamber and orchestral natures. I also listen to a fair amount of Mandopop and some Jazz, and my preferred sound signature being the ever-elusive “perfect neutral”. For this review, I’ve listened to the M9 and other IEMs on the following sources: iBasso DX200, Sony WM-ZX300, Fiio X3ii, Samsung S7 edge.

    The first thing that stood out to me when I heard the M9 in the Sony store when trying it for the first time was the coherence and detail retrieval. I find the M9 to have a very natural and coherent sound which still providing a great deal of detail. The M9 can be described to be slightly warm, with a bass boost and some treble shine. While the staging is not extraordinarily expansive, it is both sufficiently wide and deep, and separation and imaging is top notch.


    The M9 boasts a quicker and punchier bass response in comparison with most other BA IEMs. Some may even say that the bass response is slightly overexaggerated – I could sometimes feel the bass beating against my eardrums. The quality of the bass tends to be a bit direct, so it will hit you hard if the track is right. The boost here comes in the subbass, the midbass areas do not feel quite as overpowering. For me, the quantity of bass is just slightly too much, but that is coming from someone whose focus is primarily on Classical music. I feel that the bass would be at least satisfying for most.


    The best way to explain the mids of the M9 would be that it is unoffensive – one would not overly notice the quantity, yet it is not missing, at a quantity that to me is just nice. There really isn’t much to write about this – it just does its job well.


    The treble of the M9 is what I would classify as accurate and extended in a way that is incredibly precise. Piano tracks come out with crystal clarity, Stacey Kent sounds oh so sweet. This is an incredibly addictive sound – the presentation of the treble is so clean. Oh did I mention it still sounds natural? I find that strings in particular sound good in the higher registers, it comes across very clearly, without being shouty by any means.

    Imaging and tonality

    To me, this is the strongest suit of the M9 – it is fast, accurate and clean, all the while without being in your face. The M9 deals with instruments very well, be in the congested Mahlerian works, or in the more technically challenging jazz tracks. Drums come out tight and clean, and there is a very nice sheen to the cymbals. Plucked instruments – harps and double bass pizzicatos are delightful. I find the M9 to perform particularly well for orchestral and jazz tracks.

    Select Comparisons (prices at Singapore MSRP)

    Campfire Audio Andromeda (S$1,500)

    The Andromeda has clearer spacing in general for any tracks that are less congested (Jazz, etc.), but the imaging of the M9 stands out when dealing with more congested tracks (like full orchestra). The bass response of the Andromeda is slower and less punchy, with a smaller dynamic range than the M9. This is something solved in part by using the Acoustune ARC II cable, which trades some clarity and air for quicker bass response.

    I would venture out on a limb to suggest that the Andromeda does the treble range cleaner than the M9, this is probably due to the Andromeda having more space and air than the M9 – this however is a purely personal opinion.

    In general, I find the M9 to have a more natural sound and a better tonality than the Andromeda, which as many have raised tend to sound unnatural. If you prefer better bass response and are willing to trade out on some of the “air”, then the M9 would be better for you.

    Hyla CE-5 (S$1,600)

    The Hyla has a more V-shaped sound in comparison to the M9, with a more noticeable dip in response in the midrange. What the Hyla does better than anything else at this range is bass. While the quantity of the bass for M9 and Hyla is somewhat similar, the quality and tonality of the bass is a fair bit more convincing on the Hyla – it does not quite hit as hard, but with a nuance and well-managed impact that is much more pleasing to the ear. I must note that the Hyla has a very coloured sound – so if you are looking for more “reference”, this would not be for you. The Hyla in general has a more fun tuning as compared to the M9, though is not nearly as technically proficient in terms of imaging and clarity.

    Sony MDR-EX1000 (Out of production)

    I have yet to be able to do this comparison, so I will update this later.

    Etymotic ER4XR (S$499)

    It is perhaps slightly unfair to compare the ER4 and the MD+ in the same review as the M9, but I will do so anyway since it was the upgrade path for myself.

    The ER4XR has a much more neutral and flat tone, unlike the M9 which is a fair bit more coloured. In terms of technical ability, it provides slightly less in details, but does not quite present them as well. The sound of the ER4 is immensely analytical, even cold, which could make for difficult listening, unlike the M9 which you can listen to for hours.

    Massdrop Plus (~S$400)

    The MD+ has a fun signature, that is a fair bit more colored than the ER4, sacrificing details and treble extension for more well-managed bass response. What is immediately clear is that the technical ability of the MD+ is nowhere near the M9 (obviously it is an unfair comparison), where it sounds muddy by comparison. Details do not come out as cleanly, and while the midrange performs admirably, there is an obvious roll-off in the treble range that could be a major turn-off for some people.


    The IER-M9 is an incredibly technically proficient IEM that does very little wrong, beating out many of the competition at this price point (including CIEMs). It is presented in a very professional packaging, and the sound is excellent. It handles almost all genres with easy, aided by solid performances across the board, with fast and quick response, stellar imaging and plenty of details. While the staging could perhaps be wider, it does not sound intimate, and the boost to the bass is very commendable for BAs, while I find the treble extension to be natural and unforced. At the price of S$1,599, there is little to complain about for this remarkable IEM, which I have absolutely no regrets buying.


    The tracks I used for this review are as follows:

    Franck Violin Sonata in A Major, 4th Mvt, Kyung Wha Chung
    Mendelssohn Octet 4th Mvt, Academy of St. Martin in the Fields
    Brahms Piano Trio No.1, 1st Mvt, Maria Joao Pires, Augustin Dumay, Jian Wang
    Prokofiev Violin Concert No.2, 1st Mvt, Arabella Steinbacher
    Tin Sogno Di Volare (“The Dream of Flight”)(Civilization 6 theme)
    Holst The Planets, IV. Jupiter, London Philharmonic, Boult
    Mahler Symphony No.2 “Resurrection”, 5th Mvt, Lucerne Festival Orchestra, Abbado
    Prokofiev Symphony No. 1 “Classical” 4th Mvt, London Symphony Orchestra, Gergiev
    Prokofiev Piano Sonata No.7, 1st Mvt, Pollini
    Giacchino The Incredits from “The Incredibles”
    G.E.M 泡沫
    Jay Chou 听见下雨的声音
    Minzy NINANO
    Davichi Forgetting You
    Suzy, Baekhyun Dream
    Girls Next Door Deep Blue Eyes
    Stacey Kent You’ve Got a Friend
    Anne Bisson Do What You Please
    Frank Sinatra Fly Me To The Moon
    Fall Out Boy Thanks for the Mmrs


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    1. View previous replies...
    2. stormers
      is there any difference when using triple comfort tips vs hybrid silicone in this case?
      stormers, Apr 17, 2019
      Giullian likes this.
    3. Giullian
      I few the triple comfort gives a bit more bass extension and details, but only if the seal is perfect any leak the bass will drop considerable for me. Even though I really preferred the Bass with the TC, I can't handle the annoyance of adjusting the IEM every 5 min. to keep the seal. Interestingly the TC on my Andromeda S and the fit is perfect. But I still love the sound of the Silicon Tips.
      Giullian, Apr 17, 2019
      stormers likes this.
    4. stormers
      Yeah, the smooth foam kinda push out after a few min. I do notice after a few days wearing, they don't move out as much anymore. Maybe out of the box, they're too smooth and stiff?
      stormers, Apr 17, 2019


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