Sennheiser IE 900


100+ Head-Fier
Classical reinvented
Pros: Out-of-the-choir tonality tuning yielding exquisite results on classical and most other acoustic music
Class-leading bilateral range extension
Arguably best DD on the market now at the technological level
Spectacular multifaceted treble management
Clean yet very emotional bass
Deep reaching sub-bass delivering measured rumble floor
Breath-taking technicalities: “infinite layers”, wonderful microdynamics
Very extended stage, on par with closedback over ears
Custom Comfort Tips program (available in Germany only yet)
Cons: Arguably not an “all-rounder” tuning
Lean-ish high mids and female vocals
Some may occasionally like more sub-bass volume
Thin housing structure may not perfectly fit everyone’s ears
Stock tips (silicon in particular) may not fit everyone’s needs
Proprietary “MMCX Fidelity+” connectors not compatible with mainstream third party cables
It sadly took me much longer than I initially planned to put together this article about one of the most outstanding IEM sets I ever happened to audition. Also due to some unpleasant health problems, which still partly grip me, it is only now that I am able to publish my piece about the IE900s demo unit I received from Sennheiser Europe no later than last August :frowning2: .

I can anticipate I had a very big pleasure in the encounter, and I hope I’ll be able to properly convey my take on the many pluses and few minuses of this set, together with some comparison hints with their lower cost (but not lower quality) sisters IE600 and more.

IE900 currently sell in Europe for € 1499.00 including VAT. Main official product page, with direct purchase possibility here.

Full Device Card

Test setup and preliminary notes

Sources: Questyle QP1R, QP2R, M15, CMA-400i / Lotoo Paw Gold Touch + Cayin C9 / Sony WM-1A / E1DA 9038D, 9038SG3 – INAIRS AIR1 foam and/or JVC SpiralDot silicon tips – Stock cable – lossless 16-24/44.1-192 FLAC + DSD 64/128/256 tracks.

I am not writing these articles to help manufacturers promote their products, even less I’m expecting or even accepting compensation when I do. I’m writing exclusively to share my fun – and sometimes my disappointment – about gear that I happen to buy, borrow or somehow receive for audition.

Another crucial fact to note is that I have very sided and circumscribed musical tastes: I almost exclusively listen to jazz, and even more particularly to the strains of post bop, modal, hard bop and avantgarde which developed from the late ’50ies to the late ’70ies. In audio-related terms this implies that I mostly listen to musical situations featuring small or even very small groups playing acoustic instruments, on not big stages.

One of the first direct consequences of the above is that you should not expect me to provide broad information about how a certain product fares with many different musical genres. Oppositely, you should always keep in mind that – different gear treating digital and analog sound in different ways – my evaluations may not, in full or in part, be applicable to your preferred musical genre.

Another consequence is that I build my digital library by painstakingly cherry-pick editions offering the least possible compression and pumped loudness, and the most extended dynamic range. This alone, by the way, makes common music streaming services pretty much useless for me, as they offer almost exclusively the polar opposite. And, again by the way, quite a few of the editions in my library are monoaural.

Additionally: my library includes a significant number of unedited, very high sample rate re-digitisations of vinyl or open-reel tape editions, either dating back to the original day or more recently reissued under specialised labels e.g. Blue Note Tone Poet, Music Matters, Esoteric Jp, Analogue Productions, Impulse! Originals, and such. Oppositely, I could ever find an extremely small number of audible (for my preferences) SACD editions.

My source gear is correspondigly selected to grant very extended bandwidth, high reconstruction proweness, uncolored amping.

And finally, my preferred drivers (ear or headphones) are first and foremost supposed to feature solid note-body timbre, and an as magically centered compromise between fine detail, articulated texturing and microdynamics as their designers can possibly achieve.

In terms of presentation, for IEMs I prefer one in the shape of a DF curve, with some very moderate extra pushup in the midbass. Extra sub-bass enhancement is totally optional, and solely welcome if seriously well controlled. Last octave treble is also welcome from whomever is really able to turn that into further spatial drawing upgrade, all others please abstain.

Signature analysis


IE900’s general tonality is bright-neutral. The timbre is slightly lean, especially in the mids, and you can tell from the very first audition that this is a product aimed at rendering trebles in the most organic, detailed, engaging at the same time non-distorting way as possible, while in the process never leaving bass less attended to. And – boy! – if they succeeded at this!

From a more tech-involved angle standpoint, what I also very interesting to note is that they chose not to closely follow, let alone chase, any most en vague target curves out there… More on this, maybe, much later on.


One of Sennheiser’s 7mm dynamic driver’s qualities – perhaps not the most important one, but the most readily apparent to me for sure – is its extension capabilities, something very hardly heard before on IEMs, at least from my modest hobbyist’s ears.

As a direct consequence of that bass reaches as deeeep as you can possibly hear. You can safely bet the limiting factor in this case is more your hearing than anything else.

In terms of volume some elevation is present, but a modest one at that. IE900 definitely are not made to satisfy so-called bassheads, not even “educated” ones. Even for the tastes of die hard acoustic jazz lovers like me, there are times when I concede to the pulsion to adding a +3dB low shelf at 50 Hz, but that’s really occasional: in most situations IE900 sub bass is just perfect for my (quite specialised – mind you!) library.

I’ll reach even further, actually, and I would say that although not so high in elevation it’s presence is anyhow so consistent and predictable that the net effect is similar to adding a subwoofer to your nearfield setup, keeping it at a modest sound pressure level, just for “background support”, so to say.

Mid Bass

IE900’s mid bass is fast, even sculpted, yet fully textured and very expressive, emotional. This is one of the sets that renders Andrew Cyrille’s kick drum with the highest level of realism I ever auditioned.

This weren’t enough IE900, and very particularly its bass line, scale incredibly well with amping power and quality.

While in general IE900’s sensitivity is not low, so as to make them driveable to already outstanding results by relatively modest powered mobile sources, you will be totally astonished by the difference – emerging particularly in the bass section – when driving them from high quality, much higher specced amp sources.

One inter alia: Cayin C9, which I happen to have access to. Mid bass and low bass notes come up in body, viscerality and slam in a totally surprising way. It all sounds (pun intended) as if you’re sitting in a mixing studios listening to on those high end monitors hanging in there. Really, really, REALLY significant. Oh and by the way: even in such “exalted” situation, mid bass never, ever takes over on the low mids…!


Mids feel slightly recessed, if nothing else because the other parts around them (bass, and most of all high mids and trebles) come across with even bolder personality, so to say.

On the other hand their general timbre is very good if a bit lean especially in the high part, yet feels spot-on in most if not really all cases for my library.

The passage from middle to high mids easily reminds me what happens on Final’s A3000 – another, much lower tier, single-DD set featuring a remarkable (within its price class) quality single dynamic driver. And, another virtuous example of totally surprising results based on a not so common, off-choir even, tuning curve.

The passage is very smooth, of course consequence of the one driver employed, and also of the sensible taming applied to the 2-4Khz region which, thanks to driver elasticity (and, in IE900’s case, of who knows what other aspects liaised to the triple resonance chamber milled into their housings – more on this below), does not translate into overly tamed feedback in that region, oppositely it delivers a very lively, detailed while unoffensive experience.

As I mentioned before, if one remark the high mids segment calls for is some relative leanness to the notes. I feel some “butter” missing on central piano octaves, and on female vocals, to match my personal perfection. I’m not of course expecting to find the same focus on that region here that you can get from specialised sets like Final F7200 to just name one, yet as I said just a tad more of lipids would have rendered the dish even more flavoury.

Male Vocals

IE900 render baritones and bass humans with organicity and authority, and tenors, too, with just a bit of relative leanness commencing to appear on their higher registers.

Female Vocals

Female vocals are well presented, textured, clean and quite engaging. As mentioned above, they do lack a bit of body to their central notes to be astonishing.


These, together with some of the technicalities, are evidently the stars of the show on IE900.

The result is so outstanding that you can bet this must be the consequence of something really special the developers had to put in to get there: energy, expression, body, details and air, all together, while never scanting into sibilance, shoutyness let alone zinging.

A wonderful litmus paper test for this is Lee Morgan’s trumpet phrasings from 1 up to to 2 minutes into Art Blakey’s & The Messenger’s monumental 1958 Moanin’ take, from the homonymous album. Morgan instrument’s sound is full bodied yet perfectly textured, but most of all powerful yet not piercing, and far from splashy or shouty.

Such result does vary a bit in accuracy depending on eartips selection (more on this below).

Incidentally, I could only hear one other set doing better to date, but it did so only on this very particular aspect and failed in others in comparison to IE900, bass being first: a German-made multidriver unit. Oh and that’s priced 3X over our today’s reference :wink: .



IE900 stage projection is probably the widest I ever heard in an IEM, and while I think about that I would also put all closed-back overears I heard in, for good measure. There’s significant height and good depth, too !

This is another situation where IE900’s huge treble extension shows its good deeds: as many know of course we can hear sounds up to 16Khz (well… when young! :) ) but frequencies above such mark are not useless at all, as they contribute carrying information about the time it takes for sound to come back (or not come back) from the “walls around the room” – thereby helping on “drawing the stage”.

This is of course only evident when the source digital material does contain such higher frequency information, and the DAC is indeed capable of reconstructing it – which is luckily the case for much of my library, and a few of my sources :wink: .


Macrodynamics are extremely precise, positioning cues are spot on at all times, along all 3 axes.


Detail retrieval from the high mids and especially from the treble is nothing short than superb, twice as much if again we remember we are in presence of a single DD set.

I like to believe this is one consequence of those Sennheiser’s claimed designs efforts focused on sound modelling obtained via those cavities inside the housings (more on this below).

Let me add that, as an old western-economy industry bear myself, I also like to think that in addition to the positivity on the obtained result this way of proceeding is also much less prone to be “easily replied” by of some of those chifi usual suspects – building practical reproduction hurdles into one’s physical product arguably representing an even more effective method, supplemental to “mere” legal patenting, to better protect one’s industrial invention efforts in our globalised world lacking cohesive governance.

Instrument separation

Layering and instrument separation is another field where IE900 surely excel, once again especially so when considering we are talking about a single driver set.

Even on busiest (acoustic) tracks you never get a sense of congestion or mixture between voicings coming from the same spot on the stage, and the sense of depth is always granted. At times, it seems as if IE900 are able to render virtually infinite layers, such is their capability in keeping overlapping but heterogenous sounds apart from one another.

I could only hear one other IEM set till now able – on equal source gear and tracks, of course – to present me with a superior readability on low volume and/or background sounds, and that’s Softears Turii – which other technicalities, and the tonality before them, are however quite different from IE900’s so I wouldn’t easily cast a better/worse score between the two, frankly.


As en passant I previously mentioned, IE900 are quite easy to drive exploiting the power of so many at least decent mobile sources on the mainstream market, most dongles included. Their 123dB/V (corresponding to approx 105dB/mW) at 18 ohm are not a huge requirement in facts, and that’s surely a big plus in terms of crowd accessibility.

On the other hand, IE900’s note body will dramatically improve when the source happens to have the guts to push up on current delivery, this with particular regards to mid bass and mid tones.

While listening to IE900 directly paired to a Lotoo Paw Gold Touch DAP is already a lushy treat – for many reasons, first and foremost LPGT’s quite special proweness on subtle microdynamics reconstruction – you should wait until you’ll hear what you get having LPGT’s output pass through a further amplification stage, e.g. a Cayin C9 mobile set: then you’ll be in for a strong experience … :) .

Such situation can, and should, be reported both as a pro and as a (relative) limitation of the set.



I suspect not to be the only one whose first eye-impression when shown a pair of IE900 has been something like: “inconspicuous”.

Actually handling them such impression – well, at least my impression – changed radically: IE900’s housing are in facts CNC-milled off a solid piece of aluminium, which incidentally is a wonderful material I happen to know the positive properties of due to my professional involvement with it, on a completely different market.

Long story short, IE900’s housings are at the same time extremely solid and sturdy, and very lightweight.

I also do approve the choice for those thin engraving lines on the outside, which – if anything on the aesthetical level – result in a pleasant, if a bit mitteleuropean-industry-flavoured, “unglossy” finish style, and avoid overexposure to fingerprinting.

On the solidity and shock resistance there’s no question: a solid piece of aluminium gives more than the required warranties for this use case. I’m ready to bet that trampling over these ones (with their cable removed) with a car would leave them a bit dirty, but in shape.

Apart from all this, what is surely most interesting is what cannot be appreciated from the outside, and that is the internal shaping given to the housings – always by CNC-milling them – and the specially developed ultrawide range-capable 7mm dynamic driver.

The DD is responsible for offering coverage for an exceptionally wide range of frequencies for a single driver: from 5 to 48KHz.

That being not enough, taken alone, to deliver the wanted sonic result, tonality shaping is carried out by way of tree small resonator chambers, i.e. appropriate “carvings” milled into the very piece of solid AL making the housings, in-between the driver and the nozzle. Furthermore, some specialty shaping and internal surfaces finishing is put in there, to take care of smoothening excessive treble energy – and I must say with excellent results, based on my audition (see above).


Kudos to Sennheiser also for the just incredibly effective ergonomics they conceived for the shape of their IE series, which includes IE900 of course.

Even if for some reason you wouldn’t tell when seeing that somehow uncommon form for the first time, it takes seconds after wearing (any of) them the first time to vibrantly love them, and the one(s) who designed them.

On the flip – read negative – side two things are worth noting.

One: in some cases – me included – the main housing body may be a (decisive) tad too lean to match those magical proportions which fill your outer ear just enough to gain perfectly stable positioning while never feel like a swollen bean is nagging at you from out there.

It’s of course then evident that you can’t possibly design a one-size solid structure that’s so precisely fitting into everybody’s body, no matter human diversity. And in doubt, of course you’ll have to do it smaller vs bigger ! So this ain’t defect of course, yet it’s definitely an issue to manage, when it arises.

Two: again, in my case, the supply of stock tips (both silicon and foam) for one reason or the other falls short of being adequate.

Stock silicon tips have a very soft umbrella, 100% studied to get the best intended sound out of the IE900. Too bad that on the “mechanical” front it happens that, housings being too lean to stay put in my concha’s, I instinctually tend to regain firmness by pushing them deeper in. When that happens silicon tips’ umbrellas fold on themselves, totally losing the seal.

Sadly, the problem about stock tips falling short of properly fitting my canals (left one in particular) affects foamies too! Again, I suspect that’s liaised with me needing to get a higher stability by pushing shells deeper in, thereby reaching a wider segment of my ear canal, which those foamies can’t adequately fill up, not even the supplied L size.

I shared this issue with Sennheiser, and the answer has been enlightening for the sake of clarifying the origins of this situation.

First and foremost, in Sennheiser’s design intention IE900 tips should ideally “feel as if they disappear” in the ear canal, precisely the opposite of the sensation you get from bullet style IEMs, and/or triple-flanged eartips. Hence, the thinner umbrella the better, of course.

Flipping the coin, however, superlight tips intended for such precise aim will not be the best choice if for whatever reason a user prefers, or needs, to achieve a deeper fit.

I do confirm all : if – disregarding stability for a moment – I wear IE900 in a shallower position, indeed their stock silicon tips do keep the seal, and they deliver a very pleasant “feathery” sensation, or even virtually no sensation at all – as per intention.

And by the way, were it possible and handy for me, I would actually prefer such shallow fit, not being myself a die-hard fan of deep insertion – even when I use bullet-shape IEMs (which nevertheless – Sennheiser friends will forgive me – I don’t find so devilish counter-ergonomic as they reckon).

Be as it may, this finally reveals what the entire real problem is in my case: housings’ stability.

Again, in Sennheiser’s design intention, in cases like mine where the person’s ear structure is a bit too big and can’t grab the housings firm by itself, that’s where those easy-shape earhook sheaths installed on the cable (more on them below, under “Cable”) should do the trick, mechanically retrofitting the set so to say, and delivering the required stability.

So that is precisely where the game fails in my case (and not my one only).

No, to me those shapeable earhooks are super-comfortable, but not resilient enough to compensate for the housings’ eventual wobbling. That’s why I can’t personally “afford” a shallow fit, and rest comes with it.

Curtain fall ? Nevah !

First possible workaround: browsing the internet I found some sort of third party “gel outfits” – of course made some place in China. I call them “gloves”: imagine little-finger sized equivalents to a silicon smartphone back-cover. Or, similar to those winged rings you fit onto TWS drivers to help them stay firm in place. Something like this, but there are others around too.

I tried a friend’s ones and indeed those perfectly fit IE900’s housings, granting them that small body size increment that results into fitting my ear in a perfectly stable and comfortable way. And then, yes!, I can afford shallower fit and the whole stock tips game works as per design in my case too.

Alternative workaround: use third party tips :) .

Well as you can imagine I would have gone through the long tips exploration session anyhow, but in this case it was let’s say double motivated.

This article is getting already lengthy and I don’t believe that adding further smalltalk to it would make it better so my eighteen readers will I hope understand if I won’t indulge in the full report here about how I found each of the probably 15 different tip models I tried.

Suffice it to say that in the end I’m torn between two options, featuring some differences : INAIRS AIR1 foams, and JVC SpiralDot silicons.

INAIRS offer a firmer fit sensation, and their M size actually well fills my external ear canal up, thereby effectively contributing to hold those slim housings firm(er) in place for me. They also grant me better passive isolation, and a sort of delicate “softening” to some note edges (which, in itself, is not always a welcome addition).

SpiralDots feature stiffer silicon umbrellas compared to stock tips but won’t go as far as mechanically compensating housings movements, so their adoption does require either a deeper fit, or those “gel gloves” I mentioned before. The good news is that they are sturdy enough not to lose the seal when pushed deeper. Their wide bore positively contributes to IE900’s already good bass, and they yield a more crystalline timbre compared to foams.

Runnerup silicon options worth mentioning are Radius Deepmount – even better than Spiraldot on bass definition and speed, but tend to turn trebles a bit too hot – and Final E (strictly CLEAR version – black and other-coloured ones making low bass a bit “hazy”) – which deliver more body in the mids but lose some detail and precision in the treble and bass.

Last but absolutely not least, Sennheiser and their mother company being deeply involved with medical grade hearing aids and technologies, a custom eartips production service is made available – sadly only to German residents for now though :frowning2: .

It’s called Custom Comfort Tips. The rationale seems very simple in its complexity: by realising an elongated silicon tip, custom shaped following your own ear canal shape and size on one end, and perfectly slapping onto the IEM’s nozzles and neighbouring shell part on the other, you get extremely close to eliminate that personal fit variation that makes each one’s sound experience with that particular driver too much “potentially different” from its intended goal.

The program is also very well streamlined in terms of enduser fruition. It’s all centrally managed by Sennheiser, you don’t have to “look for” anything your own: place the order centrally, geoloc the supporting audiologist shop nearest to your location from a link on Sennheiser’s site, take an appointment and have your canals measured there (their service is part of the price paid to Sennheiser), wait for a few days and receive your tips at home.

The very same tips can be swapped onto IE900, IE600 and IE200. The tips’ fee is currently included with the price of an IE900 package, and a discount is offered to IE600 owners.

Those friends (lucky bastards individuals) who, residing in Germany, already could get their custom tips confirm they are indeed absolute game changers. The rest of us need to come to terms with a impatient wait :) .


IE900’s shape is designed for very easy and natural fit and this immediately traduces into supreme comfort even for very protracted period of time.

In case the housing turns out to be a bit too “slim” for one’s ears (like in my case) there’s a chance the consequent instability may be somewhat fastidious. Longer story above about the origins of this. Consequences: compensating instability by reaching down for a deeper fit may turn out to be a bit uncomfy in medium/long sessions; adopting “gel gloves” of appropriate thickness may be the best way to go.


When perfectly fitting, IE900 offer good levels of passive isolation – even more if equipped with foam tips.

In “fat concha” situations like my case, the same result is quite easily obtained by outfitting the housings with with “gel gloves” or such (see above).


It’s certainly pleasing – if after all in line with expectations vis-a-vis the package price, one may say – to find 3 different cables inside the box, each with a different hard-wired termination: single ended 3.5mm, and balanced 2.5 and 4.4mm, covering I would say 99.9% of possible needs.

Also, the freely mouldable TPU sheath applied towards to cables housing’s end allows you to shape them into the most precisely matching and comfortable earhooks you can get, exactly following your ear root line.

It’s the first time I encounter this offering, and it’s a very welcome feat – even if, as reported under “Fit” here above, it does not get as far as solving the problem of housings being too lean for my particular outer ears.

On another important note: Sennheiser’s IE-line MMCX connectors are not “everyday MMCX” fixings in reality. So be prepared: hardly any of your (my!) existing MMCX cables will fit, or safely fit :frowning2: .

Sennheiser’s MMCX implementation (in some documents tagged as “MMCX Fidelity+”) is indeed proprietary. Looking closely, the male connector coming off the tip of the cable has an additional “lip” compared to ordinary MMCX plugs. Such lip, plus a deeper, and more deeply recessed female connector, are responsible for significantly improving on connection firmness.

All good so far, the less good news however being the following two.

One I already mentioned: 99% chances are that you won’t be able to pair your IE900 with any loved individual off your thick existing herd of however good – and expensive! – MMCX cables.

The other is safely identifying the genuinely licensed (!) third parties, which would therefore be in condition to supply reliably compatible cables. Fact: between a few friends of mine and myself we experienced a few 3rd party cables sold as IE900-compatible, most of which turned into wobbly, unreliable connections. Tread lightly when shopping for cables here!!

Specifications (declared)

HousingPrecision-milled and anodized aluminium housing with internal Helmholtz resonator chambers
Driver(s)7mm XWB (eXtra Wide Band) dynamic driver featuring Sennheiser’s X3R TrueResponse transducer technology
ConnectorGold-plated “MMCX Fidelity+” connectors
CableThree para-aramid fibre-reinforced Oxygen-Free Copper (OFC) cables, with adjustable TPU earhook sheaths, each with a different fixed termination plug: 3.5mm, 2.5mm and 4.4mm
Sensitivity123dB/V = 105.6dB/mW
Impedance18 Ω
Frequency Range5 – 48000 Hz
Package and accessoriesSennheiser-branded IEM carry case with product serial# plate at the bottom, set of 3 (S M L) Sennheiser silicon tips, set of 3 (S M L) Sennheiser foam tips, Cleaning tool
MSRP at this post time€ 1499,00 (on sale in USA for $999,99 + tax now)


Sennheiser IE600 (€ 799,00 – currently on sale for € 549,00)​

Even if very similar aesthetically, and equally based on a single dynamic driver, IE600 and IE900 are quite different at the technological level from one another.

Sennheiser confirmed to me that the dynamic driver inside IE600 is a different variation (although part of the same main project) from that adopted for IE900. The same applies for the driver inside IE200, by the way.

In addition to that, housings’ builds and their internals are also quite different.

Unlike IE900’s earpieces – CNC-milled from a solid piece of aluminium and featured with 3 specially designed resonance chambers inside – IE600’s housings are 3D-printed from a special zirconium alloy by Heraeus Amloy Tech, and featured with two sets of 2 internal chambers. Such structure internal to IE600 (D2CA: Dual 2-Chamber Absorbers) focuses on treating overlapping notes coming for different instruments at the same time, helping on dramatically improving they separation, and layering.

With all this said, the sound experience offered by IE600 is for some respects similar, for others quite different from that granted by IE900.

Similarities stay in rendering clarity, and in outstanding layering and separation proweness.

The main difference is in the tonality : unlike IE900, IE600 are quite evidently V-shaped, although maybe a “wide V” at that. A more mainstream indulging tuning choice if you wish, vs IE900’s off the choir one.

Bass is equivalently speedy on IE600 and IE900, but on IE600 it is much more evident, elevated, and I refer to mid bass and even more to sub bass here. In spite of such higher elevation, bass is still perfectly readable at all times, very well textured, and stays consistently separated from low and central mids – as it definitely should – in IE600 no less than in IE900.

Another part where the two sets diverge is in the high mids, and – I would say al least in part consequently – in their treble.

IE600’s 2-4K frequencies are way more forward and pulpy, with this bringing guitars and female vocals the “butter” which is a bit left behind on IE900. However an important taming is imposed on 6KHz on IE600, I assume to avoid that their composite output would scant into shouty and/or fatiguing. As a consequence, treble detail retrieval and overall “airiness” is quite obviously less on IE600 vs IE900.

Quitting all this tech talk : choose IE600 for prog rock, hard rock, electronic music and general purpose, while – money not being a hurdle – go blind-eyed with IE900 for acoustic jazz and most of all classical music.

Such separated applicative indications, paired with ultimately equivalent proweness in doing, each one, what they are designed to do, calls for refraining from positioning IE600 and IE900 one on a higher step vs the other, and I rather recommend them as different tools to reach different pleasures, so indeed complementary to each other.

Campfire Andromeda 2020 (discontinued, was € 1099,00)​

I feel this is a quite interesting comparison not only due to the reputation Campfire Audio as a manufacturer, and the various iterations of their Andromeda set deservedly conquered over time, but especially vis-a-vis the under many respects opposite design philosophies behind Andromeda and IE900.

As everybody may remember, Andromeda are a full-BA multidriver sets, vs IE900 single-DD choice.

As a further testimony to the successful results obtained by Sennheiser on their sole dynamic driver, I would readily note that if one of the two sets may be found to deliver a tad less bilateral extension that is… Andromeda. Differences on this are small, however.

Other aspects which are very similar between Andromeda and IE900 include treble detailing, and the tuning choice to keep their 2-4KHz regions tamed down to help deliver a smooth, unshouty yet energetic overall highmid+treble section, which is indeed the case on both sets, and probable the key reasons why treble is equally delicious – beyond within some differences – in either situation.

Other similarities, or real equivalences are about stage size and three-dimensionality, with Andromeda being probably a tad deeper but less high and wide, and about layering and separation.

Tonalities are instead quite different: Andromeda is obviously warmer, consequence of some more power impressed onto 2-400Hz and some taken off from 1-2Khz. IE900 offer more airiness up above, not much resulting in terms of better clarity but rather in terms of a more realistic spatial sensation.

The most obvious differences however stay on bass note body and microdynamics: Sennheiser’s model attains to a higher level altogether, especially on the latter part – IE900 microdynamics are a very thick step above Andromeda.

As for driveability Andromeda require much less power to shine at its full potential, but conversely they require so little of that, and at such a low impedance, that many if not most sources will make them hiss, and that will of course be audible through quiet musical passages.

Beware of counterfeiting !​

It is sadly worth noting that the market is literally flooded with fake / counterfeited IE900, and IE600, and many other Sennheiser sets – and not since yesterday.

Sadly the criminals involved with this are quite skilled on delivering aesthetically near-identical products (from the boxing down to the actual items), thus posing a serious threat to the casual user when it comes to choosing and giving trust to their vendors, especially considering the important price tags we are talking about.

I happen to have access to a fake IE900 sample, which I could therefore compare with the guaranteed-genuine one coming directly from Sennheiser’s headquarters.

Sound quality wise I must say I expected a much bigger difference between the two sets. What surprised me the most was in particular the fake unit’s remarkable bilateral extension, roughly in the same ballpark as the genuine one – and that’s saying something. In terms of bass definition, note body and microdynamics, however, genuine IE900 are just straight better.

Visual counterfaiting is really staggering for how realistic it is, and how much attention and careful observation was required to discover the clues indicating the two units did not come from the same ultimate source. I took a few pictures, and shared them with Sennheiser personnel to have confirmation of my findings, and here is my report, with the hope that it might be useful to someone to avoid being frauded.

First and foremost, there was no way to spot any difference whatsoever about the printed carton box sleeve, not on the box’s internal structure and elements, the paddings etc. All apparently identical.

By closely assessing product details however some differences started to come up.

1) Cables’ earhook sheaths are not freely reshapeable on the fake unit I checked – they stay much firmer on their pristine curvature for how much you try to model them. Genuine Sennheiser sheaths are pliable almost like plasteline, and they stay in your wanted shape quite reliably while you wear them.

2) Cables’ chin sliders feature a Sennheiser logo sticker. The genuine one carries an S-logo hologram, the counterfeit one is a very obvious flattened, non-holographic, clumsy imitation. Genuine cable is sitting on top in the following picture.


3) Genuine cable’s main sheath features a smooth, uniform, solid external finish. This fake unit’s sheath carries some sort of twisted wires appearance. You can appreciate this difference, too, from the picture above – where, again, the counterfeit cable is the coiled one, below the genuine one.

4) Assessing nozzle ends, genuine IE900 should look “pitch black”, while this counterfeit sample reveals silver colour inside through a wider mesh structure, as shown by this picture.


5) The pinned plastic plate carrying stock tips should show glossy S M L size letters, not matte ones. Furthermore, genuine foam tips have quite flat tops, not bulging ones. Based on this information, try yourself to spot the genuine set in the following picture :) .


It’s of course worth noting that I could assess just one fake unit, so there is no certainty, let alone guarantee, that the above hints do apply to other cases.

Sennheiser recommends to buy new units exclusively from fully trusted, official Sennheiser distributors – and that’s a no brainer.

For second hand units – while of course remembering that channels like ebay or similar need to be taken with two grains of salt (always better than one) – a good idea is to have the seller send a picture showing the unit serial number in advance, and get in contact with Sennheiser Consumer Hearing support services: they will check if the number is reported as legit.

Considerations & conclusions

I tried to outline the multiple reasons why I believe IE900 are a beyond-outstanding product, particularly suitable for classical, and acoustic music in general, and I feel like adding some considerations at a more general level here.

What is seems from the outside is that Sennheiser did this by going back to the design board, and restart from assessing the wanted target, asking themselves how to reach it – “reinventing the wheel” if need be, and/or using more “usual” parts and competences, purging their minds from “assumed-well-established existing solutions” bias in advance.

Of course I have no real clue about their internal processes and how the real story went, but if it were a plot for a movie about an industrial success story, it might probably go as follows.

IE900’s dynamic driver itself is proprietary, made to deliver a sensibly wider range extension compared to other high quality dynamic drivers on the market. Why? Because multidrivers do struggle with tonal coherence – all of them – and, let’s face it, for good reasons too. On the other hand, existing single drivers are all “short blankets”, so to say.

So point #1 : let’s design a “wiiiiiide blanket” driver. Period. Then we see the rest.

Oh by the way: let’s do it without employing marketing-buzzword-level raw materials.

IE900’s is in the end a plastic membrane driver – such an “obsolete sounding” technology, inn’it? – yet it loops dozens of circles around others made of “newer materials”. Guess why?… :) .

I must say I feel empathic on these topics as they can’t fail reminding me that within the infinitely more modest scope of the small industrial company I currently serve in as a marketing and sales manager I often listen to my agents recursively pointing at certain innovative-name-sounding products from the competition. Transeat. Back to our plot.

Once you have an eXtra Wide Range transducer, you are still supposed to shape its sound to manage its behaviour, avoid excesses, and bend its tonality to a specific wanted target sound. This is usually done by a mix of shaping IEM shells, adding vents, filters, foams, meshes etc.

As for us: we will primarily “shape the shells” – and good luck to those who will try to precisely copy them.

Inside IEx00 housings there are milled or built (depending on the specific model’s production process) micrometrically formed spaces (“chambers”). They even got as far as studying how wrinkled their internal surfaces need to be to get the right wanted effect on sound waves passing by.

I can only remotely fathom the complexity of such a research, and the level of competences, skills, tools and budgets (!) you need to put on the table to even commence spinning such a project up. Well they did it – and succeeded.

Last but not least: once you have those grand IEMs done, based on a superbly extended driver, and tuned to consistently output the exact wanted timbre and tonality onto… lab measuring equipment (!) how about maximising the chance the same or at least a very similar result is actually appreciated by anybody’s ears – which sadly (for engineers, and luckily for philosophers) are all “guaranteed different” from the most advanced acoustic coupler mockups employed at the lab ?

Yes, you can try closing the gap by filling the commercial package with countless alternative eartips, or…

Our mother company is a leading multinational involved in hearing aids and acoustic implantations. Let’s roll out a custom eartips program!

I presume this very long stream of considerations, and their fictionalized dressings, can be summarised as follows: the old saying “when the game gets tough, the tough get playing” is of course in general an abstraction – it does take for the tough to actually be willing to get playing ! But when they do… :wink: .

Sennheiser for decades did deliver undisputed top-class headphone models (do we need to remember that HD600 originally came out in 1997?) yet they flew much lower in the rankings of IEM proposals until recently.

With their IE900 / IE600 / IE200 program they took a wholly-renovated approach to the segment, and results do show.

These 3 models lead their corresponding price brackets, and debating whether they deserve #1, #2 or #3 entry in their specific subclasses is surely very important for Sennheiser’s product marketing, their numbers etc, but for us, the users, it’s now probably just funny, loud coffee bar discussions. IE200, IE600 and IE900 are, all of them, absolute winners, and each one can easily be taken as the sole IEM one may want to own given that budget and/or that musical preference.

IE900 are light years far from being yet-another high quality high priced single DD IEMs. They can and should be narrated as a successful reinvention of the entire IEM experience, instanced onto the specific preferences of classical and other acoustic music lovers.

Sennheiser created a monumental product with IE900, and while its price tag is no doubt demanding, not a cent of it lacks justification in the multifaceted quality it offers.

IE900 is dutifully tagged on our Wall of Excellence.

This article originally appeared on, here.

Half Note

Member of the Trade: Tangzu
IE900 : Perfect headphone companion
Pros: - The comfort : even smaller than Final A series

- Build quality : it's made to be used on stage

- Sound quality is on par with other high-end Sennheiser products (thinking of the 800S)
Cons: - Tips are finnicky, although good quality (at least the Visco foams)

- Case is way too large, although it's very robust

- Cables are fairly microphonic but very good quality
This product was bought on my own without any contact with any brand, store or else. This is purely a consumer review, void of any bias or incentives. I've already had experience with Sennheiser before, in the headphones domain but this is my first in-ear product from them.

- Photos are yet to come, this line will be deleted once I've had time to shoot and upload the pics.

Edit : Head-fi seems to be precious at the moment, and I can't integrate the pics the way I usually do. So here's a link until I/they fix the image integration :

First Impressions :

The unboxing experience is on par with the price asked. The presentation is nice, although the cardboard sheet to pull out the inner box does look and feel underwhelming. The eartips are all too small for my average ears, which is surprising coming from a German brand. In the podcast on the IE series, Jermo Köhnke explains this release was aimed at the Asian market first, and it makes sense since it's the prime clientèle of the market, but including two or three tip sizes in a 1300€ package that is sold worldwide would seem reasonable. At least the large foam tips provide a decent seal and very good noise isolation, which I'd value immensely on stage as a musician.
My impressions may be skewed because I didn't pay retail price for it, but I think I'd be somewhat letdown by the basic cardboard and foam packaging if I had. Competition has gotten insanely fierce, and the minimality and simplicity of the box and accessories is now somewhat lacklustre.

The IE form factor is ace in the IEM market, and I can't stress that enough. Even well developped products usually end up hurting the ear in some way or another : pushing the concha with a shell too large, hurting the ear canal with a nozzle too large, or too long, or at an uncomfortable angle, etc. None of these issues is present with the IE900, and the result is an in-ear that you can wear for hours on end without any hint of fatigue or pain, which is nigh impossible with any other IEM I've tried.

Using the IE900 daily, it's the culmination of small details that makes it so enjoyable to use : the triangular shape makes for an easy fit, unobstrusive even with hoods, helmets, which is unheard of with any other product. The cable is a single wire and quite light, which clearly goes against the trend of woven flashy (and bulky) multi-strands cables from Asian manufacturers, but outside of your desktop setup the Sennheiser solution is much better to use. The shirt clip is a nice inclusion for musicians who pass the cable down the back, but also useful for everyday commuters that want to keep the wires from tugging on the ears. My only gripe will be that the microphonics that are quite pronounced, even with proper bending of the memory hooks. Overall, it stays in place super well and never budges out which is what all IEMs should do but almost all fail to.

Tonality :

- Tuning is a deep U-shape tuning, kinda similar to Final A series but without the pushed presence, and a ton more air. Mids are cleaner that graphs would show, and while the low mids are abundant they do not hurt the neutrality of the midrange. It's reminescent of a Thieaudio Oracle Mk1, but tilted to a flatter/less bright signature. It lands towards a purely flat signature, but with noticeable boosts in the sub bass and the air region. This isn't evident at first for people purely used to reading graphs who usually prefer seeing Harman inspired readings, but Sennheiser has really done their homework when conceiving this signature. The FR appears to have neutered upper mids, but in practice the amount is well balanced, as they rely on resonances buildup inside the ear to generate the rest of the upper midrange energy resulting in a rather neutral but U-shaped tuning, meaning it's bass and treble are somewhat exaggerated compared to real life/a neutral tuning.

Bass :
- Here's a take from my first impressions notes : "It's a stage monitor sold to audiophiles. The bass sounds like a studio subwoofer, it's very uncanny." I really stand by this definition, because when using a good amp the bass hits are massive. Insanely realistic, the replay feels like being in a studio control room. I've heard IEMs with drivers much larger, tuned with much more bass, and none of these extend as low as the IE900. My hearing's not the best by any stretch, but sine wave generators indicates I can hear down to 31Hz at fairly low volumes with this set, which is really impressive. Not only the depth but the sense of pressure is way different than you'd imagine a device this small is capable of producing. It's not only authoritative but is able to locate this deep rumble accurately in the recording space it presents, somewhat similarly to open back planar headphones, or a good studio control room.

Mids :
- The mids reminds me of my 800S. The timbre at least. In tuning, it doesn't feature the high mids to treble elevation of the 800S, so higher vocals and guitars don't feature the same energy. In that sense it's closer to EQ'ed speakers, the likes of small studio monitors. But the timbre is lovely, not to the level of Triangle paper woofers but it's definitely on par with 800S. The single driver philosophy sure works here, as the rise from low mids to upper mids doesn't feature any crossover or timbre change, as is usually the case with competition's hybrid IEMs. There is no noticeable "driver material signature" as is sometimes discussed, mostly critiques of the recent LCP diaphragm craze in the market. The diaphragm of the IE900 is a plastic polymer blend, of which we only know PU as one of the ingredients (The episode of the podcast on the IE series is my reference here) which isn't anything revolutionary, but yet again Sennheiser shows they can do wonders with ordinary materials, as they've done time and time again (the HD600, the HD800 and 800S, the 560S, all feature plastic diaphragms).

Treble :
- The amount of treble energy is very unique on this set : the early treble is low in amount, not like a sharp drop in FR but just a depression that keeps the energy to the level of the rest of the regions. Going to the higher treble, it features a higher-than-average amount that highlights one of the best features of the IE900, its spatialisation capabilities. The timbre is very good, and details are well reproduced. The finesse in the treble, the nuances in dynamics, the realism in the timbre and depth of the bass all make for an incredibly immersive experience that renders audio cues in space with superb ease, and is convincing to a point I've never heard before. In that aspect, it easily outperforms full size headphones twice its price, and manage wider soundstage with better imaging (I have in mind my experience with Audeze and Focal headphones which underwhelmed me).

Technicalities :
- Soundstage : Huge for a closed back IEM. Really accurate imaging (if you're a gaming person this is your Rolls Royce for sure) and the air amount is great at separating layers of music. The stage is helped by the sub-bass amount, the same way adding a sub to a 2.0 setup helps layering. Amazing in that aspect.

- Detail retrieval : I'm surprised a DD can be so incisive in the highs and treble. The details are not inherent to the microdynamics and the energy of the treble, but much more so in the ability to sound natural in all parts of the spectrum.

- Transients : There is a "tactile" quality to sound, a damn fast transient reproduction and the impact of the bass makes it so every detail is realistic and engaging. Every note I took during my first impressions were about the bass quality and the staging of the IE900, and for a good reason. Here are some examples :
"tricot - potage (live at Audiotree) : headboppin like crazy"
"ElephantGym - Finger (Live at Megaport Festival) : you never loose the baseline even in busy parts, the drums feel more engaging than ever before."
"Everything is so "percussive", the impression of speed is in the most tactile of meanings."

Then again, the DD is wide open and straight in front of your eardrum (you can see the diaphragm and coil when looking down the nozzle) so I'm sure it helps in this regard.

- Synthesis :
The image of being in a control room is the best analogy I can give. From the deep bass to the high end detail, to the natural mids, it's all there. You wear a studio space in your ears.

- Value :
Retail price, it's too close to the 800S to justify not enjoying the headphone experience in my opinion. If you can find a set on sale, or you're already happy with your headphones (or already owwn an HD800S), it's a fun IEM that's really worth getting and I wholeheartedly recommend it.

Conclusion :
- Final impressions : 800S, but fun and engaging ? Studio monitor you can fit inside a bike helmet ? Stage monitor with better noise isolation than ANC products ?
Well yes to all of the above. It's the perfect complement to the 800S, as you won't be left wanting more soundstage of the in-ear experience, or feel like you're missing out on details. Both prodcuts are incredibly detailed, but the presentation is different enough to enjoy both. The visceral quality of the bass in the 900 and the "tactility" I was refering to is simply addicting. The openness of the 800S and its mids neutrality will also captivate you and make its way into your brain, so there's no overlap in the two products. There's honestly very little to fault here, the product is exceptional in every way, maybe except the accessories and packaging. It's the first product I rate 5 stars and it easily deserves them all.
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Wow thank you for this thorough review! You nailed it when you said "tactility"...there's something in the texture that is hyper-realistic but not overdone (to our ears heh heh). Thank you for each and every star awarded 🙏


100+ Head-Fier
Tiny Shell, Tons of Power and a Quriky Tuning to Ruin it All.
Pros: Fit Fit Fit Fit Fit
Bass Texture
Horn and Guitar timbre
Subbass Rumble
Cons: Stock Cables are a bit odd fitting and hard to change due to recessed MMCX
Upper Mid / Treble Tuning is hot garbage
Sibilant up the wazoo
Shells are prone to scratching



Sources - Hiby RS6, Questyle M15, Apple Dongle, IHA1 Tube Amp and Q5k. Spotify for listening.

The IE900 is one of the IEMs I have dreamed of trying almost all year. The big issue with almost all IEMs is fit. It’s the biggest deal breaker and can make or break an experience listening to music. Back when I got into this hobby, Shure was a brand that made well regarded IEMs, but the key to the success was the fit. The sounds really came second. As IEM technology moved forward, we went to humongous multi driver sets that threw comfort to the wind. The pseudo CIEM like the Blessing 2, Thieaudio stuff or Fearless was the new “meta” and tiny shells were gone. 64 Audio made some respectably small shells, but nothing really existed like the old Shure IEMs that have not aged well at all. I saw the IE900 and was immediately intrigued. It is one of the smallest IEMs I have tried, but it has a huge sound. Sadly, the quirks in the tuning make this a hard IEM to recommend unless the caveats are worth it to you.

Fit: I usually don’t talk about fit or accessories as a reason to like an IEM. I look at sonic performance first, fit and accessories second. The IE900 was the opposite in my case, the fit is why I bought it and the sound is why I am not going to stay. This is bar none, the best fitting IEM I have ever worn. The shells are inexplicably tiny, sporting an all aluminum housing and 1 single dynamic driver in each shell. The insertion depth is fairly shallow, but these are the most comfortable IEMs I have ever tried. I will note that I did have issues getting a seal until I found tips that fit my ears better. After this, I was able to do 3-4 hour listening sessions with no pain or pressure build up. This is a 10/10 comfort experience.

Bass: I would be remiss to call the bass of the IE900 anything but seductive. The decay is so natural, the sub bass rumble is tight and head rattling and the mid bass punch and string plucks are beautiful. If you are a bass head, this is an amazing IEM to use (with some caveats you will read later). Before writing this review, I had called the Meteor the best bass I have heard in an IEM, but the IE900 takes the crown. A12t, Helios, Meteor, IE600 and Moondrop Variations bass doesn’t come close to the IE900. I find the tuning of the meteor bass more fun, but the timbre and the slam from the IE900 feel more natural and so cohesive that I just have to give this a strong 10/10. I don’t subscribe to driver memes, but this single DD has really hit in the bass department.

Mids: I think the mids are a real strength of the IE900. The timbre of guitar plucks, bass picking, cellos strums and strings is just not notch. Horns and woodwinds like trumpets and saxophones really sound well done, but when they reach into the higher registers of the upper mids things can go awry really fast. Flutes are disastrous, as is the harmonica. While the mids as a whole, feel well done and controlled the further north on the frequency you get the worse it gets. The strength of the subbass to lower mids in timbre, speed and detail still make this an absolute winner for me. 7/10

Treble - Upper Mids: I am combining this section because this is where it all goes very very wrong on the IE900. From the FR graph, you can see that there is very little ear gain and then a huge jump in treble creating an unnaturally airy presentation that feels disjointed from the listening experience. It’s almost like a 2nd driver kicks into overdrive to deliver sibilanc. On songs like What Would you Say or #41 by Dave Matthews Band Carter’s high percussion is more unbearable than usual. I would say when I test these songs on IEMs they are usually pretty tough on the ears, but this was worse. This was an absolutely unbearable listen. On songs like How You Like that by BLACKPiNK the vocals sound correct and normal until they start using the letter S and then I start to cringe. It feels like the IE900 gave them a lisp that makes the S super sharp. From a tonality perspective, the treble jump and huge dip in ear gain make the upper mids and treble feel both disjointed, unnatural and mostly overly sibilant and aggressive. Comparing this to other IEMs that I would put in a similar genre, Helios treble is main selling point as it toes the line of speaker like extension without sibilance. The A12t is very dark, but extends well without sibilance as well. The Meteor extends very well despite what the graph looks like. Even the Mest, which I think has by far the worst treble of the bunch, manages to outshine the IE900 in this area. The treble makes this IEM very hard to listen to. 3/10

Imaging: I usually start off my listening with one of my all time favorites, Cumberland Blues by the Grateful Dead. It has a lot going on with multiple vocalists, tons of instrumentation and a very layered mix. Vocals are front and center while the back up vocals can lean either side. The banjo is on the left behind and the guitar is a bit more centered. The stage I think falls into the above average category, but not much further. The imaging was outstanding. Each instrument was easy to pick out and the speed helped keep the high percussion from smearing. On some jazz tracks I was able to hear super fine details like shakers, brushes and chimes in a new light. I found the imaging on the Helios, Gaea and A12t to be ahead in terms of raw detail retrieval separation, the IE900 is no slouch. I think the biggest difference is this IEM has a more natural timbre making the detail feel more organic. I very much like this presentation versus Gaea and Helios. This is a top of it’s class performer in resolution, separations and detail. 8/10

So now we get to the hard part. I have an IEM that meets almost all of the criteria. It has nice warmth throughout the mids, very textured and punchy bass with rumbling subbass and the timbre for instruments is very natural and enjoyable unlike a lot of the multi driver TOTLs. To top it all off, the fit is bar none the best after getting the tips I needed. The treble is so aggressive though that I would say without EQ this IEM is not worth the price tag.

I decided with so many of my boxes being checked that I would EQ this and see if it maintains its strong points with some minor EQ.

NOTE: Blue is Stock, Green is Measured with EQ. It has a very tight tolerance for EQ and great target adherence. I don’t really care about this, but I wanted to save the IE900 so I was curious how this would turn out.

My main goal was to fix the ear gain and do a slight reduction in the treble. While I was here, I added some warmth to the mids because it made me happy. I can safely say that with EQ this is probably a top of the chart IEM for me. It maintains its strong mid timbre while the treble and mids are more solidly glued into one cohesive listening experience. More importantly, the toned down treble and slightly boosted warmth helps balance out the tonality and reduce the sibilance while maintaining air and detail. If you are willing to EQ, and fit has been an issue for you, this is an IEM I would recommend to most. I find it much more detailed and resolving than the IE600 even though it is tuned worse. I find the detail and resolution less than that of A12t, Helios, Gaea and maybe even the Mest Mkii, but the natural timbre makes the overall experience less clinical and more musical. I would take this IEM with me anywhere I bring my DAP, but without it, I think I’d avoid this one.

While I would love to give this one a good grade, the stock tuning is bad enough that I can’t do it. It can be saved with EQ, but I am not grading my EQ. I really only even tried because all of the other aspects were so close to perfect, that I needed to know what could’ve been. I will give the IE900 a solid 3/5 review and an 6.5/10 for my own score basis. It’s bolstered by fit, bass and timbre and raw resolution, but it’s let down by the strident, hot treble and poor tuning in the upper mids.
I’d say your chances are very good of that. EQ can make taking IEMs on the go a little more annoying but it probably would be fine.
Preamp: -5.8 dB
Filter 1: ON PK Fc 1015 Hz Gain -2.0 dB Q 3.100
Filter 2: ON PK Fc 1457 Hz Gain -4.1 dB Q 2.400
Filter 3: ON PK Fc 1890 Hz Gain -2.7 dB Q 2.000
Filter 4: ON PK Fc 3225 Hz Gain 6.7 dB Q 1.600
Filter 5: ON PK Fc 9390 Hz Gain -4.8 dB Q 2.000
Filter 6: ON PK Fc 13080 Hz Gain -5.0 dB Q 2.000



New Head-Fier
Review Of Sennheiser IE900
Pros: Wide and Spacious Soundstage
Lower Mid Range
Sound Separation
Lush and Warm Vocals
Cons: Sibilant and Hot Upper Treble
Dark Upper Mid Range
Bass resolution

Review Of The Sennheiser IE900



I believe there is no introduction needed for Sennheiser, As it very well renowned company for it’s audio gears especially headphones and microphones. Doesn’t mean they do not excel in areas like IEMs, TWS or any other audio gear. This German based company is the pinnacle of any audiophile dreams where he/she could find his/her endgame, well who wouldn’t. The world’s best and most expensive headphones the HE-1 is made by Sennheiser. Well in the starting of this introduction I specifically said this company doesn’t need any introduction and look at me I couldn't stop babbling about it but hey I couldn’t control myself.



* This is a loaned unit by a very good friend of mine, each and every thoughts below mentioned are my personal own thoughts and they are not fiddled with any outside influences.
*I will be referring these IEMs to as 'IE900 or Unit' for the rest of the review.
*And at last I will only be reviewing the Chu on the basis of their performance, I do not care what these are made of or packaged with when newly purchased unless it affects the sound in any sense what so ever.


The IE900 houses German-made 7mm true response transducer with specially developed membrane foil, triple-chamber absorber and acoustic vortex which helps in removing “masking resonances” for a refined and extended treble and This newly developed membrane foil minimizes resonances and distortion. These have an impendence of 16 ohms and sensitivity of 94db/1khz. The frequency response is from 5Hz to 48kHz. The sound pressure level is 123DB(1khz, 1Vrms)


The sound signature of the IE900 is neutral with bass boost. Although it sounds like more bass than neutral. This set has a warmer side to sound reproduction. Although the detail retrieval is astonishingly good. The stage is wide and open than most of the expensive IEMs.
Although being better with technical performance, This set still sounds a little weird tonally. Most probably due to the huge dip from 2k to 5k about 5-7db.



The treble is extended well but sounds sibilant and hot, Especially the guitars and cymbal crashes. When it comes to the air have a very well and detailed extension providing stage and separation. The vocals almost sound artificial or filtered. Clearly the tuning in the treble region is very weird and sounds different and the tonality is really bad for the price. I believe due to the dip between 2k-5k the sound in the higher frequency sounds wrong. The issue with this, is that the sound isn’t how I perceive in this region. Same goes for the lower treble and upper mid range, sounds dark but not dull. The lower treble region very well compliments the mix provide space and places to every sound element in the mix, Again being hot in this region, the vocals sounds shimmery.

Mid Range

This region is where I am not sufficed to say I am okay with it. The dip between 2k-5k is really upsetting. The mid range especially the upper mid range is toned down which doesn’t sound lively or energetic but relaxed where I needed this region to sound more up front in the mix. But for someone who really want a relaxed sounding mid range with excellent technical characteristics would love these definitely. Alright the upper mid range is relaxed and dark but not dull or blunt as it is enriched with details and the air and treble compliments them though still the presentation feels soft. Mainly coming to vocals the lower mid range sounds natural, heavy, mellow and lush sounding. Especially the female vocals. I find this region very beautiful in sound. The male vocals have girth and female notes have proper weight and density. Sounds warm and welcoming. And on the other hand, the upper mid range is darker and lost, I wished both upper and lower mid range balanced each other out. But you cannot have it all, I suppose.


When listening to this region, Bass sounds almost textured but not clean rather like a loose cannon. Once on the right track, bass feels confident and controls itself. Thus doesn’t messes with the mix. By first listen, these have sub bass emphasis.
Mid bass is controlled and doesn’t bloat. over the lower mid range but provides a warm sense into the mix. Still the bass isn’t punchy or thumps. But resides and needs time to resolve. This doesn’t mean it is bad in sounding, like I said the texture is refine but not sharp, clean but not very well controlled and doesn’t messes with the mix, though sounds laid back than more in front.


Technical Performance

Now when it comes to technical performance, these rock. Probably not so greatly but I love them. The sound is wide and open and the placing of instruments sounds very accurate to my listening. Imaging is not sharp, but promising separation.

Soundstage, Sound Imaging & Separation

The soundstage is really well extended in all direction, helps in imaging and separation. The imaging is okay, I don’t mind these to sound a little blunt but sounds very accurate. Same goes for the separation, I can literally pin point where each and every element of sound in the mix is coming from. The desired need of listening to listen fidelity whether a false sense or correct one, still suffice.

Speed & Resolution

Yeah the resolution is really not that great but the dynamic range of each element in the mix sounds exactly how it supposed to perform, doesn’t loose the energy here and there. The attack and decay of note hits is minutely loose,, the formulation of each note hits aren’t fast delivering or resolving quickly and to be honest for a small 7mm transducer to perform all this is really a achievement.


To conclude this review, I must say that these are made for a particular group in our audiophile community who listens to specific songs and where these dominates and establishes itself. Bass being warm and inoffensive, mid range being laid back and relaxed and treble being hot still extended very well, I believe these are one true piece of high fidelity. Despite being all I have mentioned above, overall they sound natural. I might not agree on everybody buying these, I mean come on these costs a lot. But I must insist on trying these out, maybe you will find your end game.


Sources And Tracks Used


Apple iPhone XS Max
iPad (4th generation)
Apple Dongle Dac
Moondrop Dawn
Shanling UA1 Pro
Venture Electronics Megatron
Apple Lossless
Localy stored Flac and Wav Files


Curtis Mayfield - Pusherman
Earth, Wind & Fire - September
Earth, Wind & Fire - Let's Groove
Boston - More Than A Feeling
Fleetwood Mac - Everywhere(Remastered)
Toto - Africa
The Police - Every Breath You Take
George Benson - Affirmation
Daft Punk - Doin' It Right
Daft Punk - Derezzed
Daft Punk - Tron Legacy (End Titles)
GOJIRA - Amazonia
The Mars Volta - Inertiatic ESP
Fergie - Glamorous
50 Cent - In Da Club
Jay Z - Holy Grail
Erbes - Lies
Nitti Gritti - The Loud
Juelz - Inferno
I am not sure about the accessories. If I were you, I would've have asked Sennheiser directly. I hope you got the real deal
Half Note
@Artmuzz the copper color case seems to be shipped with the earlier models, and the dark grey version is just the same as the IE600, ie they've been using the same case for the 600 and 900 going forward since the release of the 600
The IE900 doesn't use the same case as the IE600 at all. I have both, purchased directly from Sennheiser. The new case is also black, but has different material, and there's a small metal serial number plate in the back like the old copper case. I'd check with Sennheiser to verify the authenticity of this unit.


Reviewer at hxosplus
A Fine Piece of Art
Pros: - Very musical and engaging
- Realistic timbre and lifelike tonality
- Excellent, reference quality bass
- Sub - bass extension and dynamics
- Holographic and wide soundstage
- Highly resolving but not analytical
- Discrete, lightweight and comfortable
- Great build quality
- Three cables with different plugs
- Quality hard carrying case
Cons: - Slightly lacking in scale
- Treble can be a touch hot but not bright
- Cable is a little microphonic and smelly
- Limited selection of ear tips.
- May not fit well larger ears
- You may need larger sized ear tips than the included
- Custom design MMCX+ connectors will not fit after market cables
The IE900 was kindly loaned to me by Sennheiser Greece for domestic reviewing purposes and the sample unit has been returned back.
This is a translated version of my review made specially for Headfi.

I am going to skip the usual introduction and technical information that can be found in detail over here


Build quality and appearance

The IE900 is the first product to be released after Sennheiser consumer division was acquired by Sonova.
It is 100% handmade in Germany with top craftsmanship and excellent finish quality.
Aluminum is the only material used and a five-axis CNC machine precision cuts each housing individually from a single block of aluminum.
I have been reading about a handful of units with some assembly problems, mainly some kind of gluing issues at the plugs or something like that, but this wasn't the case with the review sample which was perfectly assembled and finished.
The IE900 is beautiful looking with a minimal design reminiscent of modern cut jewelry.

Fit and isolation

The earpieces are so small and lightweight that they literally vanish in the ear to the point that you forget if you are wearing them.
The fit is very comfortable, relaxing and discreet with the only footnote concerning the fact that you may need ear tips larger in size than those included in the package.
Some people with deeper, than average, ear cavities may encounter some issues getting the proper fit due to the shell shape and the short length of the nozzle, so getting deeper insertion might be a problem.
Sennheiser should have included larger and double flange ear tips to better suit individual needs
Choosing the right size ear tips is of vital importance since if for some reason you do not achieve the perfect fit then the low end just disappears.
I have achieved the best results with the supplied memory foam ear tips.



The detachable cable is of good quality, reinforced with para-aramid for better durability and it offers a great handling experience although it is prone to microphonic noise and the material is a little smelly.
The IE900 is worn around the ear and the cable features, the now out of fashion, memory bend ear hooks that offer a secure fit but are a little cumbersome.
Sennheiser, instead of designing a modular plug cable they opted to include three different cables with 3.5mm, 2.5mm and 4.4mm jacks to cover all types of plugs.
This is a little bothersome if you frequently switch sources but then, three cables are better than one in the long run.
Sennheiser uses Gold-plated Fidelity (+) MMCX connectors for improved stability and durability but while the supplied cables are of good quality, users who love cable rolling will have some trouble finding aftermarket options.


The IE900 comes with three different cables, three pairs of silicone ear tips and three pairs of memory foam ear tips (arranged in a nice plastic shorting card), a hard carrying case of high quality and a cleaning cloth.
I perfectly understand Sennheiser not including fine tuning ear tips because the IE900 tuning was done with the included ones in mind, but then they should definitely have included a couple of large sizes and some kind of double flange ear tips.


Listening set-up

As per usual practice the IE900 was left burning for about 150 hours prior to critical listening.
The acoustic evaluation was done with various sources but for the main portion I have used the iBasso DX300 with the AMP12 module and the FiiO M11 Plus.


Sound impressions

After testing dozens of iems with large, bass shaking, dynamic drivers in single and hybrid configurations, the truth is that I looked at the tiny 7mm IE900 drivers with half an eye and some kind of distrust.
I have already reviewed the Sennheiser IE300 featuring the same size drivers and I wasn't disappointed but come on, a flagship with 7mm drivers when the competition comes with huge 12mm ones?
Being skeptical and slightly biased, I started the listening tests with bass stretching material to discover in my greatest surprise that the IE900 passed all the tests with flying colors, not only offering a state of the art performance but it also outperformed most of the competition.
The quantity and quality of the low - end is just amazing to the point that one wonders how it is possible for such a small unit to produce that big sound.
Bass sounds full, visceral and weighty, deeply extending into the lower notes without rolling off, offering great sub - bass rumble, a versatile performer that feels at home from classical to bass boosted electronic music.
The tuning is balanced with a touch of warmness and the bass doesn't cloud or mask the rest of the frequencies, moreover it is exemplary layered with perfect separation between the various instruments of the bass line.
Quantity is delivered in spades but not at the expense of the quality characteristics as it is tight, controlled and crystal clear with large impact and a grand scale in dynamic contrast that is unbelievable even without considering the size of the driver.
The continuation of the auditions revealed without any doubt that I was dealing with an iem of the highest level where technical performance was top notch and addressed at birth, allowing the designer to concentrate all his efforts and know-how in manufacturing a musical communicating instrument rather than the average transducer.
With the IE900, fidelity and transparency are a "de facto" and not worth analyzing any further so we can discuss in depth about the timbre and tone of the sound.
Here the classical sound analysis into bass - mids - treble is vague and rather unnecessary since the timbre flirts intensely with the ideal, with the tonality of all instruments and voices touching reality not only in their harmonic wealth but also in their textural quality.
The IE900 is particularly resolving and finely articulated without being analytical at all, standing out by the ability to offer a deep gaze into the recording venue and masterfully communicate the inner space and time domain, virtually teleporting the listener into it, making him a part and not a mere observer.
The stage extends beyond the ears and creates a deep, three-dimensional illusion with the performers occupying their desks with pinpoint accuracy and ample space between them.
If there is something to criticize is that the picture is missing in size and scale and there is the feeling that we are listening to the music like sitting in the balcony of the concert hall.
Sennheiser's decision to stick with the time tested single dynamic driver principle paid off because the IE900 sounds incredibly homogeneous, there are no phase shifts nor frequencies overlapping and the sound is coherent and solid.
The driver is fast and agile, the iem has excellent timing and fast transient response, a sense of inherent rhythm that can keep up when the music gets busy without losing its pace.
Percussion instruments fade away and decay with the most natural and shimmering reverb, not too fast nor too slow and above all without losing in body while reaching the higher frequencies.


At the end

Well, it is not a coincidence that Sennheiser is considered to be the leading headphone manufacturer in the industry and that seems to hold true even after the transition to Sonova.
The IE900 is in my opinion, Sennheiser's best creation after the legendary Orpheus and the iconic HD650, it is more like a rare musical instrument of the highest rank committed to connecting the listener to the music.
Don't let the size fool you as it did with me and make no mistake that the IE900 is easily the best single DD iem on the planet and among the best of all kinds.

Test playlist

Copyright - Laskis Petros 2021
Last edited:
@gLer , @lmf22
Thank you very much, I am glad that you have liked the review!
Codename john
A great review makes you want to blow your money and bury your head in the rabbit hole. This was a great review!
  • Like
Reactions: Ichos
Thank you very much.
Well I have regrets that I didn't buy it but I was sort of cash back then.
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Reactions: Cris73


No DD, no DICE
Sennheiser IE 900 – A Miniature Musical Marvel
Pros: Balanced, natural, lifelike sound.
Utterly coherent and musical.
Excellent build quality, comfortable fit.
Lush tonality with excellent technicalities.
Probably the best single dynamic driver bass in the business.
Spacious stage with excellent imaging and detail.
Cons: Treble can get spiky with some recordings.
Cable is prone to microphonics.
Stock tips aren't suited to everyone.
Not the most technical performer compared to multi-kilobuck IEMs.
If you haven’t read my first impressions preview of the new Sennheiser IE 900, feel free to do so here.


The opinions expressed in this review are just that – subjective opinions, based on my personal music choices, listening preferences, and even my mood on the day. As such you should consider this (and really any) review as just another data point. If you have any questions about my preferences, the music I used, or anything else you’d like to discuss, feel free to leave a comment or PM me directly.

Full disclosure: Sennheiser loaned me the IE900 in exchange for my honest review, without fear or favour, or any expectations from me. I am required to return them to Sennheiser once I’ve written my full review, and have already purchased a pair of my own. That’s probably a bit of a spoiler for what’s to follow…



Sennheiser is a name synonymous with headphones, some of which – like the famed HD600 / HD650 series and flagship HD800 – have earned their place as benchmarks for high-fidelity in the head-fi world.

The company has dipped its figurative toes into the IEM world too, but never quite attained the same stature in the smaller format of the game as it had with its lauded headphones. That’s not to say it hasn’t been successful, and its flagship IEMs did for a time earn widespread appeal and pioneered notable engineering firsts.

But it’s been a while since the IE 800 (2012) and IE 800S (2017) were flagbearers, superseded by a new generation of multi-driver IEMs from boutique manufacturers in the US, Europe and Asia. Despite releasing a series of new IEMs in recent years, purportedly for the ‘pro’ stage and music mixing market, the company waited until earlier this year to launch its first updated ‘audiophile’ IEM, the consumer-friendly IE 300, before surprising the market with its new flagship IEM, the IE 900.

Incidentally, behind the scenes, Sennheiser sold off its consumer audio division to Swiss-based Sonova, and despite suggestions that Sennheiser’s design teams will continue working with the new owners to develop future products, could the IE 900 possibly be the last original head-fi release from the famous German brand?

Considering how the IE 900 came to be, the legacy it represents, and the fact that the HD800 was the culmination of my personal four-year journey to find the very best headphone for the music I listen to, I immediately signaled my interest in the IE 900 almost as soon as it was announced. To my utter amazement, Sennheiser answered the call, and with the generous help of one of the best industry spokespeople I’ve had the pleasure of working with (thank you, @Evshrug), I had an IE 900 delivered direct from Bavaria to my review desk at the tip of Africa.

The Sennheiser IE 900 is an outlier of sorts in the modern IEM world, particularly at the pointy (read rather expensive) end of the market where only the most enthusiastic (read well-heeled) enthusiasts dare to go.

For one, it sports a single full range (or wide band, as Sennheiser calls it) dynamic driver, instead of the mix-and-match of dynamic, balanced armature, e-stat and other exotic driver combinations common to its competitors. It’s uniquely small, unusual even for a single driver dynamic. And it uses MMCX (rather than the more popular 2-pin connector) for its plastic-sheathed (rather than braided) stock cable.

But as you’ll soon see, all these design decisions have a purpose. While they may initially frustrate some users, who may prefer the contemporary ear-moulded aesthetic or take issue with the inability to ‘roll’ their existing, expensively-acquired collection of third-party cables, once you get to know the IE 900 (and navigate around some of its ‘quirks’), you’ll find yourself rewarded with an IEM that elevates, rather than stymies, the state of the art.


What’s in the box

The IE 900 comes in a compact box adorned by a classy image of the distinctive earpieces on the cover, flanked by the Sennheiser logo and ubiquitous Hi-Res Audio emblem, a must-have accreditation for any self-respecting audiophile in the 21st century. Inside the box you’ll find…another box, this time with no imagery, just a sleek, dark-grey motif, silky smooth finish, and embossed Sennheiser logo, with a velvety pull tab on the side that releases…yet another box with the contents you’re by now desperately trying to get to.

The first thing you see after you’re done playing Russian Dolls is the two glistening silver earpieces, looking ridiculously small in their pre-cut foam enclosure. Another tab lets you lift the foam away, exposing a date-stamped certificate of authenticity with a serial number and handwritten signature of your personal QC checker, a very nice touch befitting a premium product.

Digging deeper you’ll find a smorgasbord of standard-issue accessories, including a stylish gold-brown zippered carry case, three stock cables (one for each of the 3.5mm, 2.5mm and 4.4mm termination types), a selection of silicone and foam eartips (in small, medium and large sizes), a shirt clip for playing crocodiles while listening to music, a Sennheiser-branded cleaning tool for flicking your co-workers with the earwax that accumulates in your tips, and a plush cleaning cloth to offer your co-workers by way of apology when you’re done.

I’ve seen more lavishly presented flagships (Empire Ears comes to mind), and laughably spartan ones too (Oriolus Triallii, anyone?), but on the whole, I’d say the IE 900’s is a very pleasant unboxing experience indeed. You get everything you need in the box, and what you don’t get isn’t too expensive to source elsewhere (more on that later).


Form follows function

A closer examination of the IE 900 earpieces reveals exceptional build quality and precise craftmanship. The IE 900 housing is CNC-milled from a single block of aluminium with a finely ridged ‘fingerprint’ pattern making it both very distinctive and easier to grip. It would have been cool for every set to vary the pattern slightly, like its own unique fingerprint, though that would have no doubt added unnecessary complexity and cost to the process.

The earpieces are shaped in the fold-over style common to on-stage monitors, and even though that’s not their primary purpose, it’s a design that lends itself to a very comfortable, if somewhat intimate, fit. Sennheiser opted for industry standard MMCX connectors for the IE 900, but used slightly recessed earpiece sockets to improve contact longevity at the expense of compatibility with many third-party connectors.

If you’re going to cable roll, make sure to stipulate IE 900-compatible connectors, or risk your new cable not being able to latch on to the earpieces (as was the case with a spare set of MMCX to 2-pin adapters I tried to use unsuccessfully).

Inside the shells, Sennheiser stuck with their tradition of using a single 7mm dynamic driver, made of unspecified materials, extending a lineage that dates back to the original IE 800, and possibly even earlier. While the driver itself has undergone several iterations since then, the standout features of the current implementation is the addition of two important engineering advancements created specifically for the IE 900:

X3R technology – a fancy acronym for the three Helmholtz resonators milled directly into the earphone enclosure, designed to eliminate resonance peaks that can otherwise colour or adversely affect the sound coming from the driver. The resonators work in combination with the specifically shaped nozzle structure to regulate the airwaves generated by the driver and smooth out any errant peaks in the frequency curve.

Acoustic back volume – this small ‘space within a space’ sits behind the driver and supposedly affects the tuning of low-end frequencies, helping better shape and separate them from the midrange and further reduce resonance from the enclosure.

In the lead-up to the IE 900 launch, Sennheiser released a promotional video to highlight these specific features. Check it out below:

I’m no engineer, but to my layman’s ears, one of the standout qualities immediately apparent in the IE 900’s sound delivery is a silky smoothness with an almost complete lack of resonance, particularly in music where shouty vocals or aggressive piano strikes often result in fatiguing peaks with other IEMs (especially those tuned brighter, with strident treble, or over-abundant midbass).

I’ll make more mention of these qualities in the sound impressions part of this review, but as part of my research, I asked the man who led the IE 900 design team, Jermo Köhnke, how the specific function of these tuning technologies impacts real-world performance (in a way that you and I can better understand it). This is what he said:

“The resonator chambers primarily dampen several peaks in the treble range. To me, a peaky treble is most annoying when it makes the headphones lisp and the singers ‘s’ sounds become too sharp to enjoy the music. A second effect can be unnaturally aggressive percussion, but lisping is my litmus test for peaks, which varies from song to song. Sometimes the song itself is mastered too liberally in those frequencies, in these cases a revealing headphone should transport that as well.

The back volume…gives us complete control over the tuning, so we can worry about everything else when developing the earphone housing, the assembly process, etc.. For example if you just overdo it with the mids, the sound becomes closed-in, undynamic and generally unenjoyable for music listening.
It gives us a lot of flexibility during development, but it also means outstanding quality control for the end user to get exactly the sound they listened to in a store.”

Whatever the IE 900 is doing or not doing, and regardless of whether or not what it’s doing suits your preferences, the one thing I think we can all agree on is that it’s been precision engineered by a company that knows a thing or two about tuning headphones. Sometimes the smallest innovations make the biggest difference, and this seems to be the case with the IE 900.

For more information on the various components, frequency response, THD and other technical aspects of the IE 900 design, you can download the full spec sheet from Sennheiser here.


Finish, fit and comfort

The IE 900 makes a change from the larger, bulkier, heavier multi-driver IEMs that have dominated the high-end and mainstream market for some time now. It’s a welcome throwback to more compact single-driver designs, and I applaud Sennheiser for sticking to their proven design aesthetic with the IE 900 rather than blindly following current trends.

The aluminium shells are well made, and feel refreshingly cool to the touch. They seem very resilient too, though I still wouldn’t want to drop them, and their fragile internals, from any sort of height.

I generally keep my IEMs permanently attached to their cable and stored inside a hard case or pouch, and the IE 900 is no exception. The included case is protective on the outside and softly lined on the inside, with ample room for the earpieces, cable, extra tips and even an extra cable if you need to carry one around with you. I normally like to prevent my earpieces from clinking against each other, so use a mesh case from Campfire Audio (product link here) for extra protection.

All of this contributes to what I consider to be one of the most comfortable IEMs I’ve had the pleasure of using. Comfort is a non-negotiable for me when it comes to the gear I use for several hours at a time, and the combination of small size, smooth finish and relatively shallow insert makes the IE 900 an easy recommendation in this regard.

That said, the ergonomics of the IE 900 don’t make for a seamless wearing experience for everyone. I’ve heard of several instances from very experienced IEM users I know and trust that have struggled to get a good fit with the IE900. For one, the earpieces are very light, and since they’re attached to the cable using MMCX connectors, they swivel (or helicopter) quite easily. The cable itself, while very smooth and supple, terminates in a memory wire-shaped hook that’s fairly thick, and somewhat bulkier and heavier than the IEMs themselves. If not seated properly, the cable and hook will simply yank them out of your ears with the slightest movement, especially if the tips don’t grip your ears like they should.

There’s an art to properly fitting the IE 900 that, once mastered, makes it quick and easy for me to slip them in every time. Hopefully this will help some of you who are still struggling with fit (with thanks to my wife, the ear model):
  1. First, loosely flatten out the earhook, facing the cable entry forward (in front of you and away from your face). Don’t worry about shaping the earhook before inserting the earpiece. It’s going to deform anyway, so rather save your energy.

  2. Grip the earpiece between your thumb, index and middle fingers to prevent it from swiveling around the MMXC connector, then gently insert the tips into your ear canal and corkscrew the earpieces counter clockwise while using your free hand to hook the cable around your ear. Don’t force them in, you just want enough pressure for a good seal. If pushing them in hurts your ears, or they’re going in too easily and not creating a seal, you’re either pushing too hard or the tips you’ve chosen are probably too small. Swap tipsand try again.

  3. While holding the earpiece in place, use your free hand to gently pinch and mould the earhook around the top and back of your ear. Not too tight so that it clamps your ear, but tight enough so that it keeps the earpiece in place, with the rest of the cable falling away weightlessly.

  4. If you’re still finding the earpieces aren’t perfectly seated, push the ‘bottom end’ of each earpiece (the part that goes into your ear) slightly forward (in other words, deeper into the ear). The earpieces will now sit at an angle, but should hold firm, albeit with a slightly deeper fit.

Now that you have the earpieces and cable in a comfortable position, no amount of head movement, jaw movement or light cable tugging should shift them out of place. Feel free to use both your hands to pat yourself on the back for passing the Advanced IE 900 Fitment Course with flying colours.

On cables and eartips

Before we move on to the substantive part of this review, a quick note on cables and eartips. Newcomers to the hobby sometimes get despondent when they crack open their IEMs only to find the cable sucks and the tips don’t fit as well as they should. As an experienced (read battle weary) IEM user, I almost expect to ‘roll’ the cables and tips of a new IEM to see if I can change the sound, fit, or both for the better. In fact, I’m now at the point where it’s rare that I even take the stock tips and cable out the box with most IEMs.

The IE 900 is slightly different in that the tips it comes with are rumoured to have some sonic characteristics important to the sound. According to Jermo, that’s not the case:

“The foam within the ear tips has been implemented solely to protect the transducer from cerumen or other ingresses. Foam is necessary to catch even small particles, but it’s also nearly impossible to prevent foam from building up some acoustic impedance if you compress it. If you look closely, the foam is very large-pored.

If we wanted an acoustic impact, we’d choose a finer, better-defined material. If the IE 900 were a relaxed earphone that might turn dull with a bit of impedance, [and] we would have chosen a different solution. But the IE 900 is a brilliant earphone and a slight change of 1-2 dB in the treble doesn’t change the character to the worse for most people.
Long story short, you can use whichever ear tip fits.”

So, there you have it folks, from the man himself. Stop worrying about sonic filters and proprietary tips and tip roll the IE 900 to your heart’s content!

Fortunately, I have a war chest full of third-party tips I can choose from, so when none of the included IE 900 silicone tips sat comfortably in my ears, I was able to quickly find an alternative that fit better and (as I would later discover) sound better too. Do note that the stock tips have a clever two-slot system that allows you to position the tips further forward or back on the nozzle, for a deeper or shallower fit, and that you lose this feature by switching out to third-party tips without these slots.

As for the cable, I happen to quite like the stock cable, and the fact that you get a 4.4mm-terminated cable in the box is a big plus. Yes, the included cable is microphonic when you’re fiddling and fitting the IEMs in your ears (for the uninitiated, microphonics are the loud scraping sounds you hear when the cable rubs up against your sweater or skin as it dangles from your ears).

Thankfully this is not an issue once the earpieces are seated and I’m sitting down to listen, and if I get up to walk with the IEMs, the chin slider mostly prevents any errant sounds from the cable too. But, if you’re super sensitive about cable microphonics, get ready to roll.

I’ll compare various tips and the effect they have on the sound of the IE 900 later on in the review, but I’m glad to say the IE 900 may be one of the first IEMs I’m unlikely to cable roll for the foreseeable future.

Sound impressions

In my first impressions preview I went on a musical journey of discovery with the IE 900. Now that I’ve had a few solid weeks listening to it almost daily, I have a much firmer handle on what I’m hearing and will hopefully be able to describe it without resorting to images of rainbows and unicorns.

All listening was done with the stock cable and Acoustune AET07 tips, using a HiBy R8 DAP in high gain Turbo mode at a volume setting between 36 and 44/100. I’ve also included some notes on different tips and source matching.


The IE 900 is a very balanced sounding IEM. There’s nothing in its tuning that jumps out and screams for attention at the expense of everything else. In this regard it’s not a wow tuning like you’d find with some specialist IEMs. Instead, the more I listen, the more I’m asking: ‘wow, why aren’t more IEMs tuned this way?’.

While it’s difficult to gauge how fatiguing (or not) an IEM will be after a few quick sessions, on the whole I found the IE 900 to have a fatigue-free, natural sound over the time I’ve used it. Tonally at least, I’m struggling to think of anything about the IE 900’s tuning that will fatigue even the most sensitive listener. It may not be to everyone’s preference in terms of aggression or in-your-face energy, for example, but fatiguing it simply is not.

I’ve seen the IE 900’s tuning described as V-shaped, but I don’t think that’s right. This is not an IEM that pushes excessive bass and treble energy and leaves the mids to dangle in the middle. I’m hearing a much more uniform U-shaped tuning, with a slightly lifted but otherwise linear bass, a very natural midrange that is neither too forward or too recessed, and treble with plenty of sparkle and air up top that pushes close to – but generally doesn’t cross – the brightness threshold to my ears.

All three strike a very cohesive – and importantly for a single-driver IEM – coherent balance. If there’s something prominent in the mix, you’ll hear it as prominent with the IE 900. If vocals are pushed back by the artist, they’ll stay pushed back. What you’ll get in return for this ‘hands-off’ tuning approach is exceptional quality, from the lowest sub-bass rumble to the tiniest flutter of high-frequency air. Like I said earlier, this is not a specialist IEM, it’s the consummate all-rounder.

One of the ‘tuning tricks’ the IE 900 seems to employ very successfully is a dip in the upper mids and lower treble (the so-called presence region) that lends a more relaxed tonality to the sound. It’s probably not so much a trick as it is a tuning choice, and is likely what gave me the initial impression of a laid-back listen. While I’ve since discovered the IE 900 is very capable of oomph when it’s called for, this laid-back quality is very much part of its DNA, and also what makes it so appealing to me personally (I’m not a fan of overtly aggressive transducers in any format).


Bass. The baseline measure of quality for any IEM, for me, is its bass response. With only one exception (Oriolus Traillii) I’m yet to hear any IEM that delivers perfectly natural sounding bass without dynamic drivers, and among the dynamic driver IEMs I’ve heard and own, the IE 900 is very close to the best. By ‘best’ I don’t necessarily mean fastest (it’s very fast for a dynamic driver though), or biggest (it’s plenty big, but there are bigger bass cannons out there).

By best I mean the IE 900’s bass is a delicious feast for any true bass lover. I find it very balanced between sub-bass and midbass, with a very deep sub-bass extension and healthy but not overdone midbass lift that adds just enough kick and punch.

Regardless of what’s playing, the bass seems to occupy a space just behind or just around other instruments and vocals, and as such remains distinct yet infused from and with the rest of the track. It’s a presentation that I’ve rarely heard with other IEMs, so I asked Jermo about it and he told me it has less to do with tuning than I assumed:

It has not as much to do with tuning or design… for the most part, we’re standing on the shoulders of giants here. Producing the lowest distortion sound consistently and matching channels precisely in a single transducer gives you much of the more natural impression of space.”

I’m yet to find an example where the IE 900’s bass lets me down. Not one. From synth drums to real drums, bass guitar and classical bass, woofer rumble and kick drum kick. This is a masterful bass presentation that’s impeccably tuned. There’s zero midbass bleed, and even when the bass goes big, it somehow manages to occupy a space behind or around the vocals and supporting instruments without the usual cost to microdetails.

This spatial quality of the IE 900 is clearly evident in Lana Del Rey’s Dark But Just A Game( The track has two electronic bass hits, the first at 0:26 (a soft but definite thud that should decay into the sub frequencies) and a much deeper, more resonant double-bass hit at 0:38 which then repeats throughout the track but spreads out around the vocals and instruments to give a very natural impression of the stage.

Another litmus test for bass quanity and quality is James Gillespie’s What You Do(, a track that literally opens with one of the biggest bass hits I’ve heard in a modern pop. The track’s signature synth drum explodes four seconds into the track, them repeats a few times from 0:48 onwards, and the IE 900 delivers the full, uncensored impact every time.

Unlike some IEMs that favour midbass over sub-bass or vice versa, the IE 900 doesn’t compromise either, but also doesn’t overdo the midbass to the point of midrange bleed or bloom. In Katie Melua’s Red Balloons(, for example, the track opens with a deep midbass hit and sub-bass rumble that persists through the track but never overpowers Katie’s delicate vocals at any point.

Likewise the droning bassline that makes Massive Attack’s Angel ( a go-to bass test for many people is deftly handled by the IE 900, never obscuring any of the smaller instruments or vocals and avoiding the muddiness this track can exhibit with lesser drivers. Feist’s Tout Doucement( is another track where a repetitive bassline can quickly turn into bass soup if left controlled. The IE 900 gives me an enjoyably thick, meaty rumble that underscores the sweet vocals with ample contrast and delicious texture.

I use two specific tracks to check for bass bleed: Ingrid Michaelson’s The Way I Am( and Heidi Talbot’s Cathedrals ( Both have massive bass presence, bass strings in The Way I Am from the first note, and bass drums in Cathedrals from 0:55.

The reverberating bass plucks in The Way I Am give the track its signature weight but can damage vocal and instrument detail if it's not handled deftly. The IE 900 somehow manages to infer as much heft as I've ever heard with this track while somehow leaving every other element untouched. In Cathedrals, Heidi’s sugary vocals are interspersed with sparse guitar plucks until a cavernous bass envelops the music at 0:51. If there’s any bleed, some vocal and string instrument details become obscured at this point, but not with the IE 900.

Finally, realism is a big factor in bass quality for me, and it doesn’t get more real than in Batunde Olatunji’s Stepping (Isise) ( If you want to know what it feels like to sit in the middle of an African tribal drumming melee, this meticulously recorded track is for you. The incessant, swirling, sweeping drum hits will have you bobbing your head and tapping your feet to the rhythm, but take particular note of how articulate and lifelike the texture, velocity and position of each individual drum is rendered here.

To think that the single miniature dynamic driver in the IE 900 is capable of simultaneously conveying all the subtleties (and air movement) in these ultra-dynamic drums, especially as the drummers reach a frantic crescendo at the 5-minute mark, is quite something.


Midrange. While the IE 900’s bass is almost faultless, it also never pulls my attention away from the fundamentals of the music in the midrange. This speaks not only to the balance the IE 900 strikes with its tuning, but also to the natural voicing of the IEM.

The IE 900’s midrange is firmly in the Goldilocks zone for me: just wet and full enough (especially in the lower midrange), not too dry or thin, a very natural presentation in and of itself. It has an organic quality that makes me believe what I’m hearing, particularly with vocals, but also with physical instruments like guitars and piano. Male vocals reach deep with just the right amount of texture, and female vocals have a sweetness to them that I particularly enjoy without ever being too shouty (two things I definitely do not enjoy).

Listening to the IE 900 sometimes makes me feel like the recording disappears and the artist comes to life, sitting in the same room and singing directly to me. In fact, the IE 900 pulls off this disappearing act better than any other IEM I’ve heard (a mantle previously held by the 64 Audio U12t), and I attribute this mostly to the quality of its midrange.

When I think of midrange, I think of vocals, and since I primarily listen to female vocal-driven music, this is where most of my focus has been for this review. The IE 900 is a very human IEM, in that it renders both female and male vocals with an organic timbre that’s essentially lifelike. It’s something I keep coming back to but also something I feel needs to be emphasised, because so many IEMs that go for the spectacular fall short when it comes to lifelike vocals.

The IE 900 is like a warm blanket in this regard, not that its midrange tone is particularly warm – though it is warm in the sense that it sounds alive and full – but in the way it’s just instantly comfortable and relaxing at the same time, at least with the music I listen to.

And yes, I know that the fundamentals of most instruments also fall into the midrange bracket, but I’m far less attuned to ‘issues’ with instrumental midrange as I am to vocal delivery. That said, I’ve been very impressed by the realism (there’s that word again) of real instruments with the IE 900, though I’m probably not the right person to ask about instrumental accuracy, timbre and such.

One of the first tracks I use to test for vocal purity, as I like to call it, is Beryies’ Alone ( As you’ve probably inferred, a large portion of my music library is made up of sweet-sounding female vocalists, and one of my absolute favourites is Canada's Beyries. Alone, the opening track of her masterful album Landing, isn't perfectly recorded; there's a slight glitch in the annunciation at the start of the second line (‘…so long’, 15 seconds in), that the IE 900 presents unerringly, but for the remainder of the track - and indeed the album - the vocals are just pure emotive honey.

Katie Pruitt's It's Always Been You (, another one of my all-time favourite tracks, is recorded with too much upper harmonic energy for my liking on many IEMs. Listening to this song on the 64 Audio Tia Fourté , for example, was always a love-hate experience for me, loving the detail and hating it at the same time. The IE 900, with its fuller midrange, presents an altogether more organic rendition of this track without most of the upper harmonic hissiness. On balance it's one of the best renditions of this track that I've heard (bested only by the Legend X and Traillii), which is to say it's exceptional on the IE 900.

Another great litmus test for vocal purity, Eva Cassidy’s Songbird ( melds Eva’s velvety vocals with a sparse guitar accompaniment. When Eva hits her high notes from 2:35 to 2:45, any errant upper mid forwardness will have you wincing, but the IE 900 keeps this section in check, albeit still emotionally potent.

Combining husky male and sultry female vocals, Holly Throsby and Mark Kozelek’s What Do You Say?( exemplifies the balance and linearity of the IE 900’s vocals. It’s also a good example of the IE 900’s midrange clarity, the guitars (both acoustic and electric) supporting but never subverting the vocals. From 1:49 to 2:19, both Holly and Mark and trade verses with each other to an electric guitar and rhythmic tambourine backing, and not once are the vocals pushed behind the instruments.

While not the best recording, Jim Croce’s Time In A Bottle ( doesn’t make the vocals compete with the guitar strums, which are split neatly into each channel. While Jim’s isn’t the deepest of voices, it’s still indicative of how evenly the IE 900 renders male vocals, and I’m moved by the sadness of the words, knowing the tragic fate of the artist.

This emotional connection is a repeating theme with the IE 900, which is rare for me with male vocalists, and I think it’s a factor of the IE 900’s rich and realistic midrange delivery. From Neil Diamond’s gravelly Hello Again ( to Novo Amor’s ethereal Anchor ( and Radical Face’s sublime Welcome Home, Son (, I’m finding a renewed appreciation for the male vocal collective in my library.


Treble. Treble is probably the bottom rung on my list of tonal priorities. I only really notice the treble if it’s problematic (zingy and sibilant), or rolled off too soon (dull and lifeless). I’m fairly treble sensitive, so harsh treble that calls too much attention to itself is an instant fail, but I’m not as sensitive as I thought I was to a brighter tonality, as long as the treble is inoffensive.

The IE 900’s treble is fairly smooth and inoffensive, but not quite as relaxed as say a 64 Audio Nio or Legend X. Its treble tuning is such that the lower treble is fairly relaxed but the mid-to-upper treble can, on occasion, be strident, calling more attention to itself than I’d normally like. Some instruments, like cymbal crashes, can therefore seem more pronounced than they should be, at least compared to other instruments in a track, but this also lends itself to a liveliness and sparkle with most music.

According to Jermo, this is by design: the treble of the IE 900 is at the upper end of what I consider pleasant and fatigue-free. We spent most of the development time dampening the upper frequencies to the level they are now and had several discussions about whether we need to go further.

The most common feedback I get now is if there is a way to increase the treble again. So in the end we have a common goal at the audiophile team: distortion-free and natural listening experience. On the journey to that goal, we have to make some compromises, i.e. If we want to have a strong response beyond 10 kHz, we may also have to increase the critical area of 5-10kHz slightly more than we’d wish for.”

I can probably count on one hand the number of tracks that irked me to the point of distraction over the past few weeks of listening almost exclusively to the IE 900. But yes, if I have to be critical, they’re there to be found. Whether it’s the faintly metallic tone in a small number of upper harmonic female vocals, or the peakiness of a wayward cymbal or misplaced piano strike, the IE 900’s treble, unlike its bass and to a lesser extent midrange, can be fallible with certain types of music.

A very (and I stress very) small number of female vocal recordings have also come close to sibilance, hitting a treble peak that can be uncomfortable for some, so if you’re fairly sensitive to this, an audition is probably a good idea before buying.

If I have to mark the IE 900 down on anything when it comes to tonality, its occasionally over-exuberant treble would be it. But then I’m actively seeking out issues for the sake of this review. Overall it’s still what I consider to be a very good treble response, given the single driver design that doesn’t have the benefit of multiple dedicated BA or e-stat treble drivers.

To my ears, the balance the Sennheiser team struck with the treble tuning of the IE 900 is just about right, even though I’d side with the team asking about further dampening if possible. That extra dampening would be mostly appreciated on brighter recordings, like Boston’s More Than A Feeling(, where the snares can get just a bit too splashy for my liking, and even Brad Delp’s (RIP) vocals teeter on the edge of sibilance – almost unheard of with male vocals.

On the flipside, tracks that I typically associate with sibilance, like Missy Higgins’ outstanding cover of Shark Fin Blues (, is actually very smooth with the IE 900. With the wrong IEM, Missy will ess you into submission in the opening verses, but the IE 900 seems to tame the worst of it and I find this track thoroughly enjoyable, especially when the bass rumble kicks in.

Another artist that often crosses the sibilance line is 80s starlet Sandra. I think this is more a case of her recording style, because her bright, almost hissy delivery is consistent across her albums when played back with multiple IEMs. The IE 900 actually manages to keep Sandra’s Loreen( sounding quite sedate. The pseudo-sibilant vocals are more sugary sweet than startling, and the overall balance is actually very pleasant. Who knows, I may have to dig up all my childhood favourite Sandra albums now that I can tolerate them again.

In truth, while the IE 900 can push my treble tolerance to the limit, it very rarely crosses it. High-energy dance tracks like Fragma’s You Are Alive ( are full of sparkle and shine, and I quite like what the IE 900 does with it. It’s fun, almost spiky, but not to the point of fatigue, and I find myself turning the volume up to get even more of the energy, not something I usually do with brighter music.



The IE 900 is a solid technical performer that doesn’t quite reach the lofty heights of multi-kilobuck, multi-driver IEMs at the very top of the tree (with pricetags to match). But, what it might ‘lack’ in technical excellence, it more than makes up for in one very important and often overlooked ‘measure’: musicality.

This is not an analytical microscope of an IEM I’d use to dissect the music, like Fourté , or a detail monster like Odin or Traillii. Instead, the IE 900 gives a good account of itself on every technical metric, even surpassing some far more expensive IEMs in some areas (as you’ll see below), but it’s less an IEM I’d pick on technical merit and more an IEM I’d pick for musical enjoyment.

Soundstage and imaging. Of all the technicalities us audiophiles typically like to compare, soundstage is my personal barometer in an IEM. While some people struggle to hear any ‘stage’ at all with IEMs, for me the very best IEMs are able to break down the typical in-my-head stage and trick my brain into believing the sound is much bigger than it actually is.

Some IEMs, like Fourté and Traillii, have earned a reputation for a particularly wide sound, with the tiniest of details easily audible at the extremities of the stage. While the IE 900’s stage doesn’t quite reach out as wide as those two, it’s still wider than what I’d call average, and much wider than what I’d call intimate. It also has fairly good depth and height for IEM stage (more depth than height), and with some music borders on holographic, with sounds being projected all around my head.

Closely related to stage, imaging defines how accurately (or not) an IEM positions different sounds on the stage relative to each other. For me, this is one of the real strengths of the IE 900, and part of what makes it sound so effortlessly lifelike in my opinion.

Another attribute of the IE 900’s stage is what I call ‘room feel’. Listening to the IE 900 is akin to listening to music with loudspeakers in a room. While you can’t really compare the sound of an IEM, even a great IEM, to speakers, the IE 900 is one of the few high-end IEMs I’ve heard (alongside Fourté and Legend X) that gives me a room feel sensation with some of my favourite music.

I think the best way I can describe the IE 900 soundstage and imaging characteristics is lifelike and natural, and if those words are already familiar to you, that’s because these are also the defining characteristics of the IE 900 for me.

I’ve heard Amber Rubarth’s Strive, an instrumental track off her seminal Chesky Records recording, Sessions from the 17th Ward, sound far wider and more diffuse with some IEMs than I do with the IE 900. The opening drums in particular sit a little closer in than I’m used to, but when the strings come in at 0:17 in the right channel, they are positioned farther right than the drums, almost behind my ear.

Yosi Horikawa’s Bubbles ( is another staple stage test for me (and many others), with its mesmerising drop-ball effects echoing around the stage. I’m hearing quite a bit of depth with this track, a few of the more prominent echoes decaying deep into the ink black background, but left and right I’m only hearing slightly above average width.

Al Di Meola’s Tracks of a Tear (, the opening track off his hypnotic Cielo e Terra LP, with its gentle guitar strings overlaid with swirling cymbals and a shaker that pans right to left, left to right across an ample stage, is a case in point. Some IEMs image with a three blob stage (left-centre-right) with very little information in-between, but on this track I can easily follow the shaker as it pans in both directions, not once losing its clarity or definition. Likewise I can almost reach out and touch every single cymbal strike because of how precisely they’re placed on the stage.

Vocal imaging is just as natural. Rosie Thomas’s duet with her male backing vocalist in Why Waste More Time( is notable for many things, but for me the way the two vocalists are offset from each other, just to the right and left of centre, speaks to how perfectly the IE 900 is recreating the overall image of the song.

In Kristin Hersch’s Your Ghost (, a deep, almost subterranean rumble, first heard at 0:59 and again at 1:07, echoes to the extremities of the stage and gives me a real sense of the size of the ‘room’.

A similar effect is audible at the start of Dadawa’s Sister Drum, the prominent bassline sketching out the dimensions of the stage. Then, the interplay between the larger drums at 1:59 and smaller hand drums all around them (including a prominent and surprising smack left of centre at 2:34) combines all the different elements of stage size, width, precision imaging and room feel to create a startlingly vivid image of the soundscape.

Separation and layering. I never thought a single-driver IEM like the IE 900 would stand a chance against multi-driver IEMs when it comes to separation and layering of vocals and instruments, and technically speaking I was right. I don’t think the IE 900 has the same space and air between instruments and vocals as Fourté, for example, and is a rung or two below the Trailli when it comes to layering the different sounds in a track (but then again, most IEMs are a rung or two below Traillii in this regard).

That said, the IE 900 does not sound congested, even on busier tracks, and there’s more than enough air between and around instruments and vocals so they don’t trip over each other. I’ve already covered this aspect in some detail above, but vocals are particularly well separated from instruments, and the IE 900 somehow manages to render bass on a separate level to most other sounds while still sounding completely cohesive.

Two minutes into Agnes Obel’s The Curse ( she starts to sing over a crescendo of oboe, cello, piano and some nondescript background strings and I could still make out the fundamentals of each instrument and accompanying vocals without too much trouble. It’s not as spacious or crisply delineated as I’ve heard it with the best multi-driver IEMs, but then with the IE 900 I’m generally not trying to dissect the music (as I’m doing now for this review).

Owl City’s The Saltwater Room ( is another great track with a whole range of elements vying for attention: synths, strings, drums, electronic effects, and both female and male vocals, often playing simultaneously. On some IEMs I can almost walk around the song, taking in all the different elements from different perspectives. The IE 900 is not that type of IEM. Instead I find myself listening to the music as a collective, with the different elements fitting together rather than separated and spaced apart, but at no point sounding congested.

A perennial favourite of mine, Daft Punk’s Giorgio By Moroder ( is a horrible track to use for reviews, mainly because I always get lost in the music and forget what I’m listening for. But…I did stop long enough to listen for how the IE 900 handles the busier parts of the track, starting with the sped-up section from 5:50, where drums and effects overlay some classical strings, all of which I could easily follow as separate elements if I wanted to. Then, as the track hits its crescendo at 8:05 with the introduction of electric guitars and splash drums, the IE 900 takes it all in its stride and never makes anything sound confused or congested.

Details and clarity. I’ve already suggested that the IE 900 is not a detail monster like some of the better-known high-end multi-driver IEMs with their fancy e-stats and whatnot, but that’s not to say the IE 900 doesn’t do detail. It actually sits comfortably at the upper end of the detail scale for me, but unlike some IEMs that shove detail in your face for fun, the IE 900’s details are there to be enjoyed at leisure.

Overall clarity is also in the upper echelons, with vocal clarity particularly impressive. Even though I suffer from moderate hearing loss, and sometimes struggle to make out certain softly spoken words in a loud environment, I’m hearing vocals much more clearly with the IE 900 than I do with many other IEMs, even IEMs that supposedly have unnaturally elevated mids (which the IE 900 does not).

The level of detail in the guitar strumming and plucking in Nils Lofgren’s live rendition of Keith Don’t Go( is an absolute marvel to hear. I always listen to this track right through, but if you want to jump to the highlights, the finger picking from 3:23 onward is so pin sharp it feels like the strings will cut you if you’re not careful. I can almost tell how tightly each string is wound, such is the resolving power of this IEM (and the quality of recording). The best thing about it is that it’s not harsh detail, just naturally rendered as if I’m right there at the live performance.

Fine details are also evident in the Eagles live recording of Hotel California(, which appears on the band’s Hell freezes Over LP. From the opening crowd effects that put you right in the centre circle, to the subtle differences in timbre of the shakers in the right then left channels, to the differences in tone in the three guitars used for the intro sequence, and even the deep texture of the kick drums that precede the signature guitar riff, the IE 900 gives you absolutely everything there is to hear on the recording (and even some stuff you may not have heard before).

Switching pace and genres, there’s a part in Pink Floyd’s Hey You ( that never fails to send shivers down my spine with its creepy subtext. As Roger Waters delivers the iconic line: “…and the worms ate into his brain…” (3:18), I can vividly make out the electronic effect the band used to mimic just how that must feel, and the detail with which it’s rendered by the IE 900 is utterly satisfying.

I didn’t expect the IE 900 to compete technically with some of the top dogs on the market, so I wasn’t prepared when I heard it doing just that. Listening to the IE 900 for the first time, and now even weeks later, I’m still struggling to comprehend just how it manages to pull off some of the things it does with its seemingly simple yet deceptively complex design. While it may not win every race from a purely technical perspective, it’s so far ahead musically than mostly everything else I’ve heard, price irrespective, that I question how much this actually matters.

Still, if you’re someone that favours technical performance above all else, I don’t think the IE 900 will let you down, even though I don’t consider it an IEM best suited to the analytical listener.


Select comparisons

Unfortunately I can’t compare the IE 900 to any IEMs in its price bracket and the only other single dynamic driver IEM I own is BLON’s BL-03, which costs less than the IE 900’s spare tips. My ‘other’ IEM is the legendary Empire Ears Legend X, and while I hear many similarities between the two, the Legend X has seven drivers and costs $1000 more than the IE 900, so it’s not exactly a level playing field.

Also, while I no longer own it, I did manage to briefly compare the IE 900 to 64 Audio’s Tia Fourté side-by-side, but at almost three times the price of the IE 900, it’s in a different category of IEM altogether. That said, if anyone owns or has heard any of these IEMs, the following notes could be useful.

BLON BL-03. Say what you like about one of the most hyped IEMs in the history of hyped IEMs, but when it comes to the BLON BL-03 (BLON for short), the hype is real. This has to be one of the best tuned IEMs for my personal preferences, with a spacious, punchy and tonally even sound that shames some kilobuck IEMs I’ve compared it to (I’m looking at you, Andromeda).

Compared to the IE 900, the tonality of the BLON doesn’t deviate too far from what I consider ideal. Both are U-shaped to my ears. There’s some sub-bass rolloff with more midbass energy in the BLON, but I still find the bass very clean and with just the right amount of oomph, though not nearly as clean or textured as the Sennheiser’s. The midrange of the two is similarly close, with the BLON exhibiting a little more upper mid energy, but not much, and both pull back in the presence region just enough to create a greater sense of space and prevent female vocals from getting shouty. The IE 900’s mids are significantly better defined and detailed however, while the BLON is prone to some smearing with less-than-ideal recordings. The two also share a similar treble trajectory, though the BLON is a touch more peaky and rolls off sooner, while the IE 900 can be more intense.

Where the IE 900 pulls away, in a big way, is technically, leaving the BLON to huff and puff while it sails through in every category. Both share a fairly large stage, relatively speaking, but the IE 900 is easily more expansive, wider, deeper and better defined, while the BLON is just naturally comfortable. The IE 900 images better, separates better, and its detail retrieval isn’t really fair by comparison. All that said, the BLON is still no slouch, and what it lacks in absolute technicalities it makes up for with a warm, smooth, full and easy listening sound, and is the only IEM I find even more comfortable than the IE 900 for all-day listens.

Empire Ears Legend X. Of all the IEMs I’ve owned and loved, none have matched my personal preferences more than Legend X. Widely considered to have the best bass in the business, the Legend X is actually a very balanced IEM, with an organic tonality ideal for just about any genre of music, and technicalities that sit firmly in TOTL flagship territory.

Compared to the IE 900, the Legend X – like the BLON – is not too dissimilar tonally. I hear the Legend X’s tuning as distinctly U-shaped rather than the more commonly suggested bass-dominated L-shaped curve. The Legend X definitely has more bass energy than the IE 900, but only if the track calls for it. It’s definitely more extended into the sub-bass region, with a healthy but linear midbass elevation that only gets back down to IE 900 levels around the 400Hz mark.

The IE 900’s midrange is slightly flatter and more balanced with its bass and treble, but the Legend X’s isn’t far behind. Where the Legend X improves on the IE 900’s midrange, in my opinion, is detail, being able to bring out slightly more subtle nuances without being too forward. It’s also wetter and more organic compared to the IE 900, but always clear and, to my ears anyway, never recessed. The Legend X doesn’t have quite the same treble energy as the IE 900 so makes for a smoother, slightly warmer listen overall, but still manages to outdo the IE 900 when it comes to treble detail.

Technically the Legend X improves on the IE 900 in every metric, from stage width to imaging, separation and detail. This is probably the part that surprises most people on first listen, combining an understated power and organic tonality with world-class technicalities and a balanced tuning, especially with the right (neutral) pairing and right (wide bore) tips. It may not have quite as much air or shine up top to satisfy the true treble heads, but then neither does the IE 900, and that’s just fine by me.

64 Audio Tia Fourté. This IEM probably needs no introduction, other than to say it’s one of the best and also one of the most polarising IEMs I know. With an eye-watering price of $3600 (which buys you a junk cable and a very average accessory selection), Fourté remains a technical marvel almost five years since it was first released.

Compared to the IE 900 – and BLON, and Legend X – Fourté couldn’t be more different. It has a bright-leaning U-shaped tuning that favours treble energy and clarity over midrange fluidity or bass impact. Until I heard the IE 900, Fourté was my ‘reference bass’ benchmark, with a full, impactful (when required) bass response that gives it an immensity of sound akin to full-size floorstanding speakers, though it never quite satisfied my big bass cravings. It’s not the fastest bass, but is so detailed and textured it’s almost palpable. That the IE 900 was able to match and exceed Fourté’s bass in both quality and quantity was the biggest surprise for me on hearing them together for the first time. The IE 900 also does a better job at projecting the bass coherently across and around the music, whereas Fourte’s bass is somewhat separate from the other frequencies.

Midrange is where the IE 900 eclipses the Fourté to my ears. I’m one of the few (and fortunate) to hear Fourté as fairly natural, but even I won’t pretend it’s anywhere near as natural or realistic as the IE 900, especially when it comes to vocals. The Fourté’s vocals are airy, lofty, slightly dry, and typically float around its massive stage projection, whereas the IE 900 is more grounded, lifelike, with a dead centre stereo image (when called for). A sharp dip at around 800Hz makes some male vocals slightly hollow with Fourté , and female vocals can sometimes err on the brighter side of comfortable, although the latter is more recording dependent than a flaw in Fourté’s tuning. Treble is where the two IEMs differ the most, with Fourté using its unrivalled treble extension to infuse the sound with air and detail, and doing so exceptionally well. The IE 900’s treble is still fairly energetic by comparison, but not quite as smooth or refined as Fourte’s.

Technicalities is where Fourté really flexes its muscles (and justifies its price tag). It has one of the widest, most holographic stages of any IEM ever made, combined with clinically precise imaging, masterful separation, and more detail than the human ear could possibly resolve. This isn’t always to Fourté ’s advantage, however. The IE 900 is far more forgiving of poor recordings, for example, and is also more consistently musical. The IE 900 is also more natural as a result of its slightly narrower stage, and to me sounds more lifelike too.


Odds and ends

The IE 900 is fairly source agnostic, which is to say it’s going to sound great from just about any source. While I normally only use it with HiBy’s flagship R8 DAP, with its detailed, balanced, and slightly warm-of-neutral reference tuning, I enjoy the IE 900 just as much from my LG V30+ smartphone (with its drier, brighter Sabre DAC delivery), and even, on occasion, with EarMen’s Sparrow (review here) and TR-Amp DAC/amps (review here).

Interestingly I find the IE 900 to be both easy to drive and very power hungry at the same time. With a 16-ohm impedance and a sensitivity of 123 dB (at 1 kHz and 1 Vrms), it should be very easy to drive, yet requires the longest turn of the volume dial of all my IEMs to get it to my comfortable listening volume. To me that suggests the IE 900 is scalable, and will probably take well to even more powerful desktop amplification, though I have no such amplification on hand to verify my suspicions. I can say for certain it’s not sensitive to the point of exhibiting any hiss whatsoever with the HiBy R8, even on full power, and the R8 is prone to hissing with overly sensitive IEMs.

Eartips, on the other hand, can and do affect the sound profile of the IE 900. As mentioned earlier in the review, the included tips are not required to filter the sound of the IE 900 or tame its treble in any way, so whatever you may have read to the contrary is incorrect. Out the box I didn’t like the fit or sound of the stock silicone eartips, and since I don’t enjoy using foamies, didn’t even try the stock foam tips for size. But I did try several different tips with the IE 900, each with its own quirks and qualities, so thought it might be useful to include some of my findings below.

Acoustune AET07 – this is my preferred tip for the IE 900, which I hear as clear and exceptionally detailed (especially in the midrange), with a powerful, almost visceral bass response that travels through the stiffer stem and tickles my ears across the super soft umbrella-like silicone. It also gives me the widest, deepest stage of all the tips I’ve paired with the IE 900. The 07 can be quite revealing though, so poorly recorded brighter tracks may have you reaching for one of the warmer tips below.

JVC Spiral Dot – this is easily the most comfortable tip, with its soft, pillow-like silicone and pliable stem. The IE 900’s nozzle lip (which really should be standard issue on all IEMs) ensures the tips don’t slip off in my ears like they do with most other IEMs, and there’s enough of a gap between the IEM nozzle and tip opening for the ‘dots’ to do their sonic magic – i.e. soften and shape the treble and accentuate the bass decay. Compared to the Acoustunes, Spiral Dots do indeed soften the sound, making vocals slightly more ethereal and ‘distant’, but also smoothening the treble peaks while retaining most of the bass impact. If you’re finding the IE 900’s treble a bit spiky for your liking, try on some Spiral Dot tips.

Sedna EarFit/Light Short – closer to the Acoustune sound but with more contrast between bass and treble, the Sednas are a great choice with the IE 900, if you find them comfortable. The harder silicone of the Sednas makes them more noticeable over longer listening sessions (and not in a good way), and while I still find them comfortable with the IE 900 compared to other IEMs I’ve used them with, the combination of harder sound and harder fit compared to the Acoustunes makes them only third best for me.

Spinfit CP500 – I got these tips more out of curiosity than anything else, since I’ve never really gelled with Spinfits for some reason. These are longer than the other three tips above, and even though they’re made of soft silicone and have the trademark Spinfit bend when inserted, I still find them less comfortable to wear for longer sessions. Sound-wise they have a softer bass response than the three tips above, but also a more balanced tuning, so if you think the IE 900 is too dynamic and powerful for your liking, the CP500 might tame them for you – assuming you manage to keep their very wide stems seated on the earpieces and not in your ears.


Closing thoughts

I still remember when, in my early days in the hobby, Sennheiser’s IE 800 – with its black ceramic shell and twin-turbine aesthetics – was an aspirational IEM for me. When I finally got to hear it for myself, I was won over by its warm, full sound, ample bass and great staging, but left disappointed by its permanently attached, jangly, single ended-only cable and less than ideal, bottom-ended fit.

The IE 900, if it is to be the IE 800/S successor, is a major and worthwhile upgrade in every way. From styling to build quality, sound quality and accessories, it takes pride of place as not only the best IEM Sennheiser has ever made, but in my opinion, the best headphone Sennheiser has ever made, bar none. It even eclipses the HD800 which, for me, is the pinnacle of dynamic driver headphone design.

Whether or not Sennheiser will continue raising the bar in headphone design under new ownership remains to be seen. What we do know is that, in the IE 900, they have created a flagship worthy of the brand, and worthy of the heritage. A single dynamic driver design that’s both effortlessly musical and technically excellent, without ever sacrificing the former for the latter like so many other flagships (and even some of their own headphones) tend to do.

Like any IEM, the IE 900 is not without its flaws. The flipside of its easy going tonality is a treble that pushes too close to overexuberant for my personal liking, though it’s only ever crossed that line once or twice with the music I regularly listen to. Other nit-picks I could point to would be the occasionally microphonic cable, odd tip selection, uncommon MMCX connector design, and occasionally unconventional fit.

All that said, the IE 900 is one of the only high-end IEMs that’s truly engaged me from the very first listen, not with the spectacular, but rather with its balanced, natural, lifelike and completely non-fatiguing presentation of the music I love. It’s an IEM that, more than most I’ve heard before, removes the artificiality of the recording chain and connects me directly to the music. I’m in the room with the singer, on stage with the band, in the studio with the mixer. I’m hearing real drums and real guitars and real voices in an utterly realistic space, and not for a minute is my attention drawn away from the experience.

Put it in your ears, hit play, and you quickly forget you’re listening to an IEM. It’s a human experience that has less to do with technology and more to do with the people behind it:

I couldn’t devise an acoustic target that makes off-the-shelf transducers sound good enough that they practically disappear. It’s 90% the transducer technology and all the developers and engineers working for decades to make this performance possible.

The [real] stars for the IE 900 in particular are Grit Bonin, the acoustic engineer who implemented my target and requirements into the product, and Heinz Epping and Maike Faulhaber, who made world-class simulation efforts to optimise the last bit [of performance] of the transducer. Finally, André Michaelis, who initially headed the development of our 7mm transducer 16 years ago, and also convinced upper management to make a ten-digit investment to build the most advanced transducer assembly line in the world.”

The IE 900 is now the first IEM I reach for when I want to relax, want to connect, or want to explore new music for the first time, knowing I’ll be hearing it like it’s meant to be heard. It’s my miniature musical marvel, and comes with my highest possible recommendation.

@Dust by Monday not worried at all. I have an IEM Vac from FiR Audio that I regularly use to 'clean' my IEMs. As long as you're careful and practice good ear hygiene you'll be fine. If you're concerned, you can take the foam inserts from the stock tips and put them in your aftermarket tips.
Dust by Monday
@gLer Won't the foam inserts fall out into my ears if there's nothing to stop them? The sennheiser tips have a cross shape in the tip opening that prevents this piece of foam from falling out.
Grandios, dies ist Geschichte.
Großartig ✨🌟
Schöne Grüße aus Italien .
Giorgi ☮️✌️


1000+ Head-Fier
Sennheiser IE 900: One of the Best I've Heard
Pros: Excellent all-round.
Realistic soundstage and imaging.
Deep, detailed bass with great textures.
Cons: None for my usage (but if you plan to use these on-the-go, the cables are microphonic).
I had the IE 900 for two weeks, with over 150 hours. They are so aaamaaazing! Not only do they sound great, they are so light and comfortable. The IE 900 is so good that I sold my other IEMs, including the Campfire Audio Polaris II, Dorado 2020, Solaris 2020, and gave my UM Mest II to my dad. All of these IEMs are excellent in certain areas or genres of music, but I feel the IE 900 is the best all-rounder across the board, from musical qualities to comfort.

I’m using the Sony WM1A (MrWalkman custom firmware Dawn Plus). DSEE AI on, DC Phase Linearizer Type B Low, low gain, 4.4mm balanced output.
My music preferences are: Pop, country, jazz, and occasionally classical.

I'm skipping the unboxing, technical description, and walkthrough of the accessories. Other reviews are much better at doing that than me. Let's just get right to the sound!

The bass
The IE 900 has the best bass I’ve heard in an IEM. It goes deep when needed, but doesn’t artificially make every bass note deep and big. They are clean, detailed, and beautifully textured. The same goes for bass quantity; there is plenty of it, but only when the music has it, and never interferes with the lower-mids and mids. The bass quality reminds me of my home stereo system (PSAudio DirectStream Jr DAC, Octave V70SE tube integrated amp, Dynaudio Contour S3.4 speakers).

The mids
So beautiful, articulate, and detailed. Both female and male vocals come through strong and natural; never shouty or thin. The small details of familiar singers’ voices come through better and has better textures without overwhelming my ears with too much details. They are much more natural than other IEMs I’ve heard.

The highs
Extended and very smooth. Silky smooth. Some burn-in (either the IEMs or my ears or brain) is needed for the treble to shine. Initially, they seemed bright, even when using foam tips. After about 100 hours, they calmed down and became well extended and smooth. Instruments sound natural and non-fatiguing. This is important for me because I use IEMs when I work, so don’t like IEMs with distracting and fatiguing treble.

Soundstage and imaging
Both the soundstage and imaging are very beautifully done. The soundstage is moderately wide and deep, with a good amount of height. Sounds extend slightly outside my ears and around my head. What I like is that the soundstage is natural. It’s intimate if the music requires it, and extended if the music has it. More importantly, the soundstage doesn’t extend too far out where it can become unnatural, like an artificial 3D effect. Imaging is excellent. Every instrument and vocal has their own space and music rarely sound crowded. But please keep in mind these are not magical IEMs; poorly recorded/mix/mastered music still has poor soundstage and imaging. I would say the IE 900 presents the soundstage and imaging as they are in the music.

One of the most comfortable IEMs I’ve ever had. I can use them throughout my workday and rarely had to take them off or adjust them. I also like how extremely light they are. The comfort and weight don’t distract me from the music, which allows me to get more immersed in it.

The cable
I really like the cable. They are light, hard to tangle, and has a nice neutral color with a slight shimmery look under bright lights. They are more microphonic than other IEM stock cables, and may not be good when you’re using the IE 900 on-the-go. The shirt clip helps a lot. This drawback doesn’t bother to me because I use these in the office or at home.

Accessories and ear tips
Love the small case. The Sennheiser logo on the front looks great. The serial number on the back is a nice touch, and makes me feel special 😊

I’ll write some brief impressions of the ear tips I’ve tried. Keep in mind these are highly subjective (I tend to like sounds can be described as smooth, slightly on the warm side of neutral, and even slightly rolled off highs while retaining airiness). The sound descriptions may not apply to your ears, but hope they will give you an idea of how each tip can change the sound of the IE 900.

Stock ear tips
Out of all the stock ear tips, my favorite is the foam (size S). I like them with the small foams in them, which gives the sound a very slightly smoother treble.
I got a good fit with the medium silicone ear tips with a shallow insertion. I was not able to get a seal with the small or large sizes no matter the kind of depth of insertion.
+ Light and airy sound.
+ Excellent detailed and deep bass.
+ Very extended highs.
+ Very comfortable. They seem to just sit in my ear and doesn’t exert much pressure.
– Poor isolation (this can be plus if, for example, you’re working in the office and need to hear colleagues when they try to get your attention).
– The highs can get fatiguing for long sessions with poorly recorded music, but it’s fine with well recorded music.

I got a good fit with the small foam ear tips. The medium and large sizes put too much pressure in my ear canals, resulting in discomfort after about 15 minutes.
+ Full bodied sound.
+ Deep bass (but not as detailed as the silicone tips and can sound muddy with bass-heavy music).
+ Fuller sound, especially great for vocals.
+ Very comfortable. Slight pressure but never got uncomfortable.
+ Good isolation.
– Slightly rolled off highs (can be a plus because they are more forgiving of poorly recorded music, and good for long listening sessions).

Third-party ear tips
My favorites are the Final E (size S). I also like the Symbio F (size S).
Final E
+ Deep and bold bass with nice textures (but not as detailed as the stock silicone tips).
+ Full mids (much fuller than the stock silicone tips).
+ Smooth highs (need to have a deep insertion, otherwise the treble rolls off too much and you lose sparkle and air).
+ More body across the board.
+ Comfortable for long sessions.
– Slightly rolled off highs, but can be a plus because it’s more forgiving with poorly recorded music.

Symbio F
+ Detailed mids.
+ Great highs for foam tips; only slightly rolled off (less roll off compared to the stock foam tips).
+ Comfortable.
– Mids can sound grainy depending on the music.
– Bass doesn’t go as deep and there’s less of it.

Campfire Audio Marshmallow
+ Comfortable.
+ Forgiving sound for modern pop music.
– Rolled off bass and treble.

Symbio W Peel
+ Comfortable
+ Great bass quantity, but I not as textured as the stock silicone or Final E tips.
+ Smooth mids
– Treble doesn’t sound natural.

Azla SednaLight (regular and short versions)
– Easy to lose the seal in my ears.
– Bass sounds strange. I can’t put my finger on what it is.
– Highs can be fatiguing with modern music. More so with the short version.

Spiral Dot ++ and Spiral Dot regular
+ Comfortable
+ Forgiving sound for modern pop music.
– Diffused imaging. No solid center image. The vocals are too spread out.

Spinfit 145
+ Comfortable
– Muddy bass and midrange

(Photos have the Symbio F ear tips because the orange color looks great in photos :stuck_out_tongue_winking_eye:)


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hello vs sony iem z1r which one is better? I'm interested in these two

Scuba Devils

Headphoneus Supremus
Sennheiser IE 900
Pros: Incredible all-rounder
Excellent fit/comfort
Wonderful bass
Non-fatiguing crisp treble with stunning detail
Perfect width soundstage
Cons: Silicone tips aren't great...

I want to share some thoughts on the IE900 after almost two weeks of daily use. I’m sorry to say I’m not sufficiently technical to address in a way that many look for, as such, it will be a layman description with the knowledge I do have where possible. I am a music lover for many years (and once upon a time 90s DJ...) and up till last year, mostly listen via my separates systems and a variety of headphones and earphones - as of last November, I didn’t even know what a hybrid IEM was, let alone a single DD or an EST driver, they were all just earphones, headphones and some were Bluetooth (of which I've a few gathering dust)! My journey over the last few months with IEMs has certainly been obsessive, expensive and incredibly enjoyable - I’ve heard music in ways I’ve never before and I now rarely listen via my main system or full-size headphones. I admit to being a fan of Sennheiser and have had a few of their products over the years - HD-25-1 being a go-to back in my DJ days, HD650 (which I never use) in more recent years and a trusty set of IE8 that served me well for about 8 years, only actually finally retiring them last year as this hobby took hold. I’ve learnt a lot (but not enough) in the last few months and met many great likeminded music fans, I plan to continue this voyage of discovery and strive to be more proficient to articulate what I ‘hear’ into words that are useful to others… but for now, this is about as good as I can give!

I have a demo unit as I worked in consumer electronics for many years and still in touch with old colleagues. The unit is on loan but I will certainly be buying.


Most home listening has been via the Sony NW-WM1A or Sony ZX507 for out and about portable use. Some listening later on via the L&P W2. They are hungry enough compared to the MEST MKII, on the Sony NW-WM1A, I need to crank up to the late 50s (out of 120) somewhere on high-gain, versus maybe early 40s on the MEST. Still plenty of room though.

Current IEMs in order of purchase:


So what do I think?

First and foremost, I absolutely love the IE900 - right now, if I could only keep one of my IEMs, it would be this - mostly due to being the most solid all-rounder of any IEM I’ve heard in terms of its ability to handle any genre. In addition; the size, weight, form factor are perfect for any situation - walking, in bed, wandering about the house etc. I walk 5k every morning with my dog and I look forward to getting up at 6am to get these popped back in my ears - likewise during the day while working, finding moments to get lost in the music for a few minutes, even just while making my lunch or getting through some admin that doesn’t require much brainpower. I keep looking at others in my collection and thinking I must give them a shot, but then nah, IE900 it is…


Sound Impressions

Soundstage feels wide and natural, a well-positioned ‘stereo’ sound, instruments very well positioned and where I expect to find them relative to general listening experience of music over the years. The MEST MKII in comparison is somewhat wider but absolutely ‘taller’ too and much more 3D - this is good for some music but definitely not all - for example, I love it on well recorded ambient music, especially very cinematic albums - I’m not as keen with a lot of rock albums though, I find it can sound a bit unnatural at times, instruments a bit off in terms of positioning - a thought though in this regard, is it just I’m not used to hearing a delivery of this nature and need to get used to it?! But on MEST with genres that suit, that 3D tall and wide delivery is stunning and certainly a keeper in that regard.

In spite of the wide soundstage, I still feel a very centrally focused low-end delivery - I feel like the focus zone is in the middle of my head but separating out as appropriate for the instruments. I actually love how it ‘sits’ in my head, I really feel with kick drums for example that they thud in both ears perfectly to land a central delivery… reminds me of beat-matching kick drums back in the good old DJ days and I actually crave this position with other IEMs at times.

IE900- ZX507.jpg

Some of my test tracks had deep sub bass sitting alongside pounding kick drums - all wonderfully controlled and I keep wondering how the heck something so small is capable of this. I find the bass more obvious compared to the MEST MKII, not sure if its better per-say - I think going back to my reference to its position is where it shines - potentially a personal preference as opposed to one being better than the other.

The higher register of treble is an area that I tend to shy away from in music delivery - often choosing with audio system over the years to EQ bass up and treble down, probably the techno/house DJ in me. I’ve been concerned about this and look out for comments in reviews when considering purchases that might suggest an IEM is bright. Much to my surprise, yes the treble is more evident than I would expect to like, it feels like its fine-tuned marginally below a point where it could be an issue, but instead sounds wonderful and adds so much to a detailed, pristine and analytical delivery - I’ve yet to find it harsh on any music and again, often amazed how there is so much detail from a single driver.

IE-900 Package.jpg

There is a sense of being slightly recessed vs the MEST, a more forward centre on the MEST for sure which means for some vocal tracks, especially male vocals on the lower end of the scale that they can feel slightly back - not to the point that it bothers me personally but I do note at times.


The cable is excellent and very similar to the IER-M9, looks almost the exact same - slightly stiffer though and a small amount of microphonics if not correctly positioned around my ears and with the chin thing (what’s it called?!) - but easy to position and when out walking, I get zero cable feedback. The ear hooks are quite stiff and bend well around my ears - a slight concern here is when bending them over my ears, I wonder is this putting strain on the MMCX connectors that might damage over time?


The tips didn’t work out that well for me, I couldn’t get a good seal with any of the silicone tips and they sounded pretty poor as a result - I tried them first and was incredibly underwhelmed, bass was absolutely feeble as best. Switched to the included large foam tip and a whole new world opened - wow! I did ultimately switch to Comply TSX-500 in medium as I get an even better seal and no impact to SQ, unlike with some others where bass becomes way too much and overall too dark, not the case here at all - the TSX-500 seem to have a relatively medium bore size. Isolation is great - when walking, I can hear louder traffic but not enough to interrupt my listening, at home sitting in my kitchen as I am right now, I can’t hear any other noise in the house, including my wife talking to me… is it terrible to admit my frustration with having to unplug an IEM and ask my wife to say whatever she said again, only to find its a reminder I need to cut the grass or something? - she should know I have important listening to do.


Anyway, I would struggle to say whether I prefer the MEST to the IE900, they are both incredible IEMs in their own right but as noted, the IE900 would probably take the prize given how they can be a jack of all trades with any genre in any listening situation. I’m not exaggerating when I say they often take my breath away, I’ve stayed up way past my bedtime several nights over the last couple of weeks as I just want to keep listening, I’ve even broken my no wine during the week rule and had to pour a glass to accompany my listening bliss! They definitely complement each other well though and I will certainly be submerging myself in the MEST again soon for longer sessions.

They are unbelievably addictive and in my humble opinion, absolutely worth the price tag. Apologies again that I can’t address areas that a lot of folks here would like to know and I hope this was somewhat useful. I’m conscious there is a lot of interest in this IEM and I’m very lucky to have one before launch, as such keen to share what I can. Still early days too but I do feel comfortable at this point with my findings.

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So far I am truly enjoying my IE 900, and now I am afraid that I will be using my IE 800 S and IE 800 rarely in the future.

For me both silicon and foam adapters work perfectly fine. I use small size and both snuggly fit into my year. I primarily use silicon and swap it with memory foam. Memory foam give me slightly more isolation. I really wish if the adapters are a bit longer to have deeper in-ear fit. Will see if Comply would release any professional series in the future.
How's the IE900 compares to M9?
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hello vs sony iem z1r which one is better? I'm interested in these two