Sony IER-M9 In-ear Monitor Headphones

General Information

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)




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

Latest reviews


500+ Head-Fier
Pros: + Superb fit and comfort. Extremely lightweight.
+ Superb isolation
+ Incredibly coherent and well-balanced
+ Versatile tuning
+ Vigorous DD-like bass. Robust, impactful, defined, taut, with near-DD decay. Significantly tauter, more defined, more authoritative, and more impactful than the Sony XBA-Z5.
+ Fantastic soundstage across all dimensions. Not quite as ‘out of your head’ as the IER-Z1R, but incredibly satisfactory nonetheless. Much larger than the Sony XBA-Z5 and Campfire Andromeda OG.
+ Open, spacious presentation
+ Ultra-precise imaging
+ Impressive instrument separation
+ Remarkably, effortlessly resolving
+ Great speed
+ Outstanding treble extension and detail; crisp, airy, and refined
+ Great value
Cons: x Lacks the dynamism and physicality of DD bass
x Lacking in 'fun factor'
x Somewhat hard to drive
x Sensitive to tip selection and insertion technique

Spotify Premium on Mac > iFi ZEN DAC Balanced > iFi ZEN CAN Balanced > IER-M9 w/ Sony Hybrid tips + 4 Core 22AWG OCC SPC Litz 4 cable

I'll keep this brief:

My main drivers over the past year have been the 2014 Sony flagship XBA-Z5. Despite their age, I've yet to encounter anything around the $500 price point that matches their unique speaker-like presentation. I'm primarily a bass and soundstage head, so the Z5 fit the bill nicely, but I wanted to more out of them technically.

I bought the M9 blind, and kept my expectations checked, having read that they didn't match the Z5 in terms of soundstage, and having found the tonality of the all-BA Fearless S8F decidedly uninspiring despite its V-shaped tuning. I had also previously owned the AK T8iE MKII and extensively auditioned the Campfire Andromeda OG, and was frankly underwhelmed by their performance given their entry price.

Let’s just say the M9 has single-handedly disabused me of the notion that TOTL IEMs offer only “incremental refinements” above mid-fi units. To my ears, the M9 sit confidently in a class of their own, just below the IER-Z1R, and well above the AK T8iE MKII, Campfire Andromeda OG, and Fearless S8F.

Crucially, as several users have noted, the M9 are especially sensitive to tip selection and insertion technique. From my listening experience:

Non-ideal fit = Stuffy, overly-warm, thick, laidback, blunted transients, small soundstage

Ideal fit = Clean, quick, precise, open, airy soundstage, extended treble

Due credit to @CoryGilmore for the following tips:
  1. Use the smallest sized tip that provides the deepest possible insertion and seal without creating a vacuum/suction effect
  2. Pull the top of the ear up and back when inserting IEM—this minimises pressure from within the ear canal, and mitigates the vacuum/suction effect.
Highly recommended.
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I had the same issues with insertion, it was a hassle of 3 days to find the right tip size.

Additional tip: After they are inserted, quickly jiggle/wiggle the unit while softly trying to push them further in. This sometimes helps them getting more inside without creating under or over pressure.

Sounds silly but works awesomely good. This tip is actually from the Sony Manual :D at least the japanese manual says to quickly jiggle/wiggle them around to get them deeper inside without creating any preassure.

You know that they are properly inserted when the sound doesn't (or only very marginally) change when you mover your head around, raise your eyebrows or tension your jaw muscles by biting.


100+ Head-Fier
The Overlooked Silent Assassin
Pros: Soundstage
Instrument seperation
Incredible vocals
Cons: Very very infrequently upper mids shrills
The Sub 1k IEM market is one which has heated up ferociously in the last few years. Especially with the likes of Chi Fi manufacturers getting traction and even starting their own cult house SQ etc. Makes finding a good bang:sound IEM increasingly difficult.

I have been on this mission for the last 2 years (see my previous reviews). I've been through pretty much all well known manufacturers from 64 audio to campfire audio to beyerdynamic and Sony.

Every time I thought i'd found the one, i'd find myself finding flaws in the SQ or loose interest shorly after.

Right off the bat, these are not neutral nor as some have purported sterile. They are warm and have a slight bass boost.

Now take this with a grain of salt (i'll edit the review later if it changes over the next few weeks), but, the Sony IER M9 are hands down the best most coherent sounding IEM i have ever heard.

- MBP - 3.5mm
- E1DA G3 - 4.4mm
- Tidal Master
- The M9 even though rated at 20 Ohms responds remarkably to amping, the more power you give them the better and better they sound (much like the Z1R). Balanced is the way to go to power these.

Music Tested:
- Pop, Hip Hop, EDM, Rock and occasional Indie

Unboxing + Accessories:
- Blows everythign sub 1K (aside from the beyerdynamic Xelento which is on par) out of the water. Class act by sony
- Cables are great.
- Nit picking, the case like the Z1R is over engineered and stupidly annoying to store.

- Very easy to get a good seal and good fit. The IEMs themselves are very light and contour naturally to the concha.
- The selection of tips allows a fit for everyone, silicone tips do produce at times a negative pressure effect due to venting on the IEM - can be circumvented by superiorly tugging your ear when you insert the M9 or doing a valvalsa whilst it's insitu.


- Bass (9.5/10)
eing a self confessed bass head this was my biggest fear getting these IEMs that the bass was going to be lackluster and trash compared to DD bass on the Z1R.The bass on these are exceptional for a BA. Very much comparable to DD bass. These sound nothing like other BA bass (that is the CA Andro's), the bass is thick has a decent amount of rumble and even has the subwoofer effect. Sony have done something marvelous with their inhouse BA drivers. The bass is fast and has great attack. Precise. The only better Bass (technicality wise that is, not quantity) is the Z1R which had even better sub bass extension and rumble. Plenty of other DD and hybrids with more Bass quantity, but none this well executed (if you don't believe me listen to Take me back to london by Ed Sheeran). If the song has prominent bass, you get prominent bass. Never bleeds into mids and is suberbly executed. Well done Sony. -0.5 for the comparitvely less sub bass extension (i know not possible for a BA, but still)

- Mids (9.5/10)
The best vocals i have ever heard on a pair of IEMs, bar none. These outperform the Z1R in the mids easily. Male and female vocals are superbly executed, crystal clear with no distortion. High octave female singers can sound slighly blunted at times, but again minor caveat. On the very rare occasion the upper mids sounded shrill and artificial, however this seemed to be track specific. -0.5 for the occasional shrills (i need to reitorate, very infrequent, maybe more related to track mastering as it was only on 1 to 2 tracks out of 50)

- Highs (10/10)
I've never really been able to assess highs very well. I'm extremely treble sensitive so take what i say here with a grain of salt. The highs are clear and at no point in any tracks was there silibance or harshness. No matter how high you turn up the volume. Cymbals sound accurate and precise. There isn't much ariiness (compared to the Andros) but i never really cared about that.

- Soundstage + Seperation (10/10)
The best seperation out of any of the IEMs i've heard. The layering is simply exceptional. From memory the next closest would have to be the Tia trio which also had great seperation and layering, but after time sounded boring and unentertaining. The sounstage is wide, vocals still sound intimate but not in your face. The coherency is outstanding. These are very easy to listen to for extended periods of time without being being fatiguing.

I think i can finally say i have found my endgame IEM. These are simply outstanding. I've gone through so many IEMs which i would keep for a week, a month and sell on. From the moment i heard these i knew they were the ones that will never get sold on. Unfortunately i don't have the previous IEMs to directly A/B but from memory these are a carbon copy of the Z1R with less bass, better mids and substantilly better highs - that is i found the Z1R sibilance unbearable. These easily beat out the CA Andros, Alas, Vega , 64 Audio Tia Trio, EE Legend X, Beyerdynamic Xelento and even Sony's own flagship Z1R. For me this is now the TOTL benchmark.
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Headphoneus Supremus
Pros: Outstanding mid-range and coherency
Great imaging
Comfortable, lightweight, good build quality
One of the better cables out there + 4.4mm included!
tip selection and case
Cons: Minor nitpicks: slightly too warm for my tastes

The Sony IER-M9 originally came out at the MSRP of $1499 but has since dropped down to $999 in recent months. This puts in the shouting distance of other multi-BA IEMs like the Hidition Viento and the Moondrop S8. Unfortunately, I have not had a chance to hear the S8 yet, but I was very excited to try the IER-M9 and see how it stacks against my custom Hidition Viento-B.

This unit was sent on loan to me by community member, tma6. Thanks!


The IER-M9 is a 5-Balanced Armature driver in-ear monitor that features a black magnesium housing with a carbon fabric looking decal in the front. The shell is very lightweight, surprisingly, and feels premium. It also is very comfortable in my ears and I had no issues wearing these for long periods of time due to the nice shell design, weight, and comfort. The cable is also wonderful to use.

In fact, the silk-braided cable is housed in a nice soft rubbery-sheath that is easy to move around, unwind, and doesn't tangle easily. It terminates in an L-connector of both 3.5mm and 4.4mm varieties. Yes, there are two cables included in the box. The connectors of choice for the Sony IER-M9 is mmcx, it fits in a recessed opening on the M9 shell.

In addition to the cables, the M9 comes with 13 sets of tips to choose from, as well as a carry case, and a series of other accessories. The unboxing for the M9 is quite nice, though still lacks to the drawer box approach of the IER-Z1R.

Sound Impressions
The Sony IER-M9 was mostly paired directly with my Sony NW-ZX507 digital audio player for the majority of the time I used it for this review. I also did try it alongside the Topping A90/Schitt Bifrost 2 combination, and an iPhone 5S. The Sony-Sony pairing is a popular one in the community and I've seen a lot of impressions of the M9 paired with the 507, so I was excited to see how these aligned with my own thoughts.

As general blanket statement, I found the Sony IER-M9 to have a warm, enjoyable and extremely coherent signature with outstanding mid-range and and generally laid-back and almost boring sound signature. I use the term "boring", not necessarily in a negative way. It's just an inoffensive sound signature that doesn't have any stand-out feature in its tonality/timbre that makes it either wrong, colored, or the like. I wouldn't necessarily call the IER-M9 reference tuning, as I do find it a little warmer and a little dark, but not overly colored.

Let's start a little differently this time that my normal reviews. I find the M9's coherency outstanding. The multi-driver setup seems to be well designed and doesn't show any disjointed sound across the board. Add to that the really strong resolution, and it seems like Sony knows a thing or two about how to make a good sounding cross-over setup and maximizing each driver's potential.

In the same sense, this is the same experience I found with the Hidition Viento in both the universal and the custom versions. Like the M9, it also featured great coherency and good resolution despite having less drivers than other models which tout tons of drivers. More does not always mean better.

To go on further with the comparison to the Viento-B, I find that both share a lot of similarities. The M9 does have 1 additional BA driver, but both are priced similarly now, and have outstanding mid-ranges where everything just sounds accurate and reproduced well. They both do lack some of the resonance and natural decay that comes inherently sometimes with the use of a standard balanced armature driver, but that's fine for their use cases.

Where I do find that they differ a little bit is in the tuning. The Viento is more reference neutral to me, and when compared to the IER-M9, the Viento has a more focused upper mid-range and even treble region, that may sound a little bright and lean compared to the M9. The M9's additional warmer lower-midrange also adds more body to the sound, and one can't really go wrong with either of these for a solid multi-BA setup under $1K. It's more about picking your tonal preferences.

Okay, I skipped a bit from my normal routine, and now I not only spoiled how I feel about the M9, but also how I compared it to what I consider it's biggest competitor in it's price class. Let's move forward with some music discussion.

I found the M9 to really go well with singer-songwriter type music. I listened to a lot of James Taylor with the M9, and really enjoyed how it presented the softer acoustic guitar songs of the famous musician. The bowed bass guitar on "Fire and Ice" has a nice amount of rumble can be pictured just slightly behind the rest of the instruments in this track, lying a little further back in the scene with its soft growl. The guitars are just over to the left of my hearing, and Taylor's voice is dead center, perhaps a slight bit to the right. The effortless vocals are shown in all their greatness with the M9, and the warm body really helps give his tender vocals in this track some character.

I didn't talk a lot about imaging characteristics a lot until just now, and I do think overall that the M9 excels in this area. It has a nice soundstage that isn't exactly wide or super deep, but it's a good playing field that's above average width and in the upper tier in terms of depth. This allows instruments to sound well separated and it makes the M9 sound open and free of chaos in the most chaotic tracks like Daft Punk's Contact.

The entire lead-up to the finale of this track sounds very detailed and intricate on the M9. The kick bass hits with some authority even if it does not have the slam and decay of typical dynamic driver like it's older sibling, the IER-Z1R. The cymbal crashes sound accurate but not over-done and this constant beating can sometimes be fatiguing on many headphones and in-ears. Again, what is most impressive on the M9 is how effortless it handles the battlefield of this track, with instruments smashing in all directions as it leads to its final build-up and closure. There's no muddiness, no meshing of sounds, and no blunted sounds. Everything comes in well-defined and clean.

My current addiction drug is Tingvall Trio, and specifically their "In Concert" live album. I'm finding myself craving the track, "Movie," for it's sweeping piano melodies, and constant snare drum attack, and heavy bass notes that keep everything gelled together. I normally enjoy this type of music with my Viento and Hifiman Arya, both more reference and neutral-bright signatures. But the added bass warmth of the IER-M9 does give the low end a little more body and power to it. The slightly darker treble helps give these types of songs a nice romantic-type sound approach that is easy to enjoy for long periods of time, while not losing any of the soundscape.

I've said a lot of praising remarks to the IER-M9 and the question to be asked is, where does it rank and will you buy it?

The second question is a quick, "no." And it's not because I don't like it. I do like it, but I don't find it different enough than what I own now to make it a purchase. I already have the Hidition Viento-B, and its tuned closer to my neutral preference target, and I prefer a little more air, and a little more upper-mid range than what the IER-M9 provides, but in many ways, I could go either set, as a stand-alone multi-BA IEM to use .

As far as the first question, I think the M9 stands on and near the top of the IEM playing field. It's not the best multi-BA IEM, as I still believe that title goes to either the qdc Anole VX or the 64 Audio U12t, but it's that small tier below where the Hidition Viento and Vision Ears VE8 reside for me.

At $1000, I think this is a nice buy that comes with a great accessory package and a great build. It has a few minor flaws, that are more preference things than anything else, but that's typical in this price category where preferences matter more. Good work Sony.
Excellent review, the comparisons with other IEMs and the description of how they sound with specific tracks are clear, understandable and valuable. Having owned the M9 for half a year I find the description very accurate. Really well done.