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Sony IER-M9 In-ear Monitor Headphones

  1. yukitq
    The Spectacular Sony IER-M9
    Written by yukitq
    Published Dec 7, 2019
    Full Review can be found on my site: https://audiorambles.com/sony-ier-m9/

    Build Quality, Fit, Comfort and Isolation
    Aesthetics (8.5/10): Matte Black shells, decorated with a carbon-fibre faceplate. A classic look, for sure, yet still awfully handsome to look at.

    Build Quality (9/10): The housing of the M9 is made with Magnesium Alloy. I can’t say I’ve much experience with the material, but they feel sturdy to the touch. The MMCX connectors are made such that they do not rotate, always a plus in my books for longevity. Included cables are resilient yet fairly supple, and are tangle-proof. All in all, not quite glorious Nippon steel, but fantastic in their own right.

    Fit and Comfort (9.5/10): Yes, while you might not think these Frankenstein-looking housings might fit well, they’re actually insanely comfortable and ergonomic to wear. The housings contour to my ears wonderfully, and never feel like they’re in danger of falling out. I could and have worn them for hours at a time without fatigue.

    Isolation (9/10): As a general rule, if they fit well, they’ll likely isolate well. The norm, not the exception, the M9 blocks out a substantial amount of noise for your busy commutes on the Subway.

    Bass (8.75/10): During my initial audition with the IER-M9, my expectations regarding the lower frequencies were not set very high – the M9, after all, sports solely Balanced Armature drivers which are often not considered optimal for the reproduction of bass notes compared to traditional Dynamic Drivers. Upon firing up my usual test tracks, however, it was quickly apparent that I had underestimated these little monitors.

    The texture, decay and weight of the bass produced by the M9 is eerily similar to that of a DD, high praise for Sony’s in-house made balanced armature drivers. A general weakness of BA Bass is its propensity to sound thin and artificial, but the M9 reveals none of that. The slight bass boost in both the sub and midbass regions raises the “fun” factor, while still exercising excellent restraint. Bass is always exceptionally clean, tight and agile, highlighted by demanding drum-heavy tracks like Muse’s “Neutron Star Collision”.

    Sub-bass extension is also fantastic, reaching all the way down to the lowest registers, considerably unique also in its ability to make it “felt” rather than “heard” compared to other BA setups. The rumble did, however, leave more to be desired, lacking the grunt and texture the Z1R can bring. All in all however, it’s stellar bass from the M9.

    Midrange (9/10): One of the more frequently levied criticisms of the M9 is that it can sound “boring”, and this sentiment likely stems from the M9’s midrange presentation. It’s without significant peaks, neutral sounding and just ever slightly recessed in terms of stage presentation. The amalgamation of these factors ultimately contributes to bringing about the aforementioned impression many get with the M9.

    The midrange however is still very much excellent, with the former mostly an issue regarding personal preferences. I do find myself clamouring for greater midrange presence at times, but objectively, the midrange of the M9 is supremely capable. It boasts fantastic clarity and detail, though perhaps just a fraction behind resolution kings like the 64Audio U12t or the Anole VX, given its greater emphasis on smoothness ahead of transparency, due to the slight touch of analogue warmth present.

    Male vocals are some of the best I’ve heard on M9, perfectly conveying the velvety, rich texture of vocals such as Frank Sinatra’s and Andrea Bocelli’s like few monitors on the market can. While their female counterparts do still sound airy and natural, the M9 lacks the sparkle and brightness in the upper midrange register to really make singers like Adele stand out.


    Treble (8.75/10): The lower treble on the M9 is exceptionally tuned, with sufficient sparkle to make cymbals and hi-hats shimmer and shine, on tracks like the Jackson Five’s “Want You Back”, detailed with natural decay. Far from what would be considered an intense listen though, it retains the smoothness characteristic of the M9’s sonic signature. Upper treble on the other hand has been tuned down a notch, as instruments like Trumpets on classic Jazz Standards such as “LOVE” or “Autumn Leaves” sounding neutered and unexciting, albeit still with good resolution and articulation. In the same vein, extension is unimpressive, with roll-off evident in the highest registers, once again illustrating the M9’s predisposition to favour a relaxing and non-fatiguing listen over exhibiting sheer technicalities.

    Soundstage, Imaging, Separation and Timbre (8.75/10): Even against the backdrop of the prior praise I’ve lavished, the imaging and separation capabilities of the M9 are by far their most outstanding quality. It isn’t hyperbole to say that they’re likely the best I’ve had the pleasure of listening to in that regard. While the stage of the M9 is just slightly wider than average, and its depth relatively unimpressive, the sense of space created by sheer imaging and separation ability will floor you at times, especially in genres like Jazz (Count Basie for example), or live recordings. It’s an experience like no other, and therein lies the “wow” factor of the M9. The M9 also avoids most of the timbre issues full BA setups can have, possessing sufficient weight and decay to its sound. They’re great and generally a non-issue, unless you’re overtly nitpicky or anal about it

    As if it were ever in doubt over the course of the review, the Sony IER-M9 gets an easy recommendation from me for those in the market for a warm-neutral type sound signature. For those who want something non-fatiguing to listen to, yet still brimming with technical ability, the M9 checks all the boxes. And you get to unbox a high end Sony product. Furthermore, they’re relatively inexpensive compared to majority of the market in the TOTL department. Did I also mention you get to unbox a high-end Sony product?

    All hail our Japanese overlords.
  2. 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. Ocelitgol
      is there any difference when using triple comfort tips vs hybrid silicone in this case?
      Ocelitgol, Apr 17, 2019
      Giullian likes this.
    3. CrocodileDundee
      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.
      CrocodileDundee, Apr 17, 2019
      stormers likes this.
    4. Ocelitgol
      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?
      Ocelitgol, Apr 17, 2019