Sennheiser IE 900 Review

Sennheiser IE 900 Review

Sennheiser IE 900 Review

Sennheiser’s production of all things audio, from microphones to headphones, makes them a company with no need for introduction. When I take a trip to my local headphone shop to try all that good stuff that I can’t afford, I frequently find one of the IEMs from Sennheiser’s IE line staying in my ears for a little longer than usual. Today, I have the pleasure of reviewing the highest caliber unit from the line: the Sennheiser IE 900. Let’s take a look in the box before we go over some of the special tech that gives it its special sound.

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What’s In The Box?

-Sennheiser IE 900 IEMs

-3 Headphone Cables: 1 pin MMCX to 2.5, 3.5, and 4.4mm.

-3 Pairs IE Series Foam Ear-tips

-3 Pairs IE Series Silicone Ear-tips

-Semi-firm Case

-Anti-static cloth

-Instruction manual

-Certificate of Authenticity

-IEM Cleaning Tool


Look and Feel

There are two aspects to the IE 900 that jump out: it’s shiny, one-piece aluminum housing, and it’s microscopic size. This doesn’t happen very often, but the unusually small size actually took some getting used to when getting them into my ears. There was, however, a trick: pushing them as deep into the bottom of my concha as possible, and then pushing them as far into my ears canal as possible. After realizing this, my issues with fit became minimal. Though I’m usually a silicone ear tip kind of guy, opting for the foam helped provide an additional grip to my ears – and also exposed how much more comfortable the IE line of foam is versus more generic foam tips (which frequently irritate my ear canals). The wires provided don’t do much to help with the fit: a firm but malleable material encases the part of the wire that gets wrapped around the ear, meaning you’ll have to bend it manually to the shape of your ear. While this is a bit annoying at first, the wire develops a memory that over time takes less and less adjusting.


Don’t get me wrong – once I have these in, they’re extremely comfortable. There’s even a decent degree of additional passive isolation offered by the “L” shape design that vaguely mimics the stellar isolation of the Shure SE846 (-26dB vs. the SE846’s -37dB). I’m also quite a fan of their straight forward metallic design that conveys a certain audiophile brutalism. But the peculiarities of such a small fit are worth mentioning.


Design and Technical Specs

The Sennheiser IE 900 has a number of impressive technical design elements that contribute to its excellent sound (don’t worry, more on that shortly). For starters, the IE 900 employs something called acoustic back volume; an additional chamber within the acoustic chamber controls air direction as it moves through the transducers. This provides extra clarity in its low-end boost, and helps keep low-mid and bass frequencies distinct from one another. Also of note is the 7mm X3R TrueResponse transducers that provide even further clarity. Helmholtz resonator chambers are also included in the technical design, which provide yet another level of clarity by eliminating standing waves.


The IE 900’s housing is one-piece aluminum. This gives it an extremely durable build, as one piece housing lacks hinges, screws and other structural weaknesses. Lastly, gold plated MMCX connectors provide maximum resistance to tarnishes.

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Frequency Response: 5 Hz to 48kHz

Impedance: 18 ohms

Driver: Dynamic, Extra Wide Band

Sensitivity: 123 dB

Passive Isolation: -26 dB


Sound Stage

The imaging capabilities of the IE 900 are incredibly wide and fast. The level of layering and clarity this provided really can’t be overstated. Separate rhythm guitar tracks playing identical parts opposite to one another on the left and right sides were clearly heard as two separate tracks with distinct, idiosyncratic differences. Acoustic guitar transients were felt as if they were playing the ridges in my skull like a washboard. A particularly jarring experience I had with its imaging was when I was listening to “Cradling Mother, Cradling Woman” by Fleet Foxes. Background voices quietly present at the beginning of the track felt like they originated from the back of my skull before wrapping towards the direct sides of my ears. Though I didn’t experience an external three dimensional quality with the IE 900, it had a very vivid internal 3D quality, scooping out the inside of my head and filling it with every symmetry and asymmetry present in a mix.


Just looking at the frequency response graph would leave you feeling mislead once you have the IE 900 in your ears. It would appear on paper that these are for bass heads, but I really can’t say that that was my experience with the unit. Bass was abundantly present, but never showed up where it wasn’t welcome. It’s rare for a bass heavy headphone to retain a “mix intended” sound, but it sounds to me like that’s exactly what the IE 900 is doing. Kick drums heavy in mid bass were hit with extra punchiness without unnatural sub-bass add ons. Conversely, kicks heavy in subs rumbled smoothly without tempting the IE 900 add any sludge in the mid bass and low mid region. Though mid bass and subs were approximately equally present, the boosted high frequency transients inform how the low end is heard, and give it a punchy quality. Also worth noting is the surprising physical vibrations that manage to moderately rumble throughout the IE 900’s tiny housing.



This may likely be the theme of this review: perfectly transparent and tastefully balanced. Once again, the mids profile betrays what you think you might see on the frequency response chart. Mids sound fully present, with guitars, synths, vocals, and other driving parts of tracks getting expressed with an extra high level of accuracy and fullness. Though I’m getting excited to start talking about the high end, the mids struck me as the most refined part of the sound, as they were tastefully shaped while avoiding the all too common “scooped” sound. Low mids that are abundantly present in tom-toms had an impactful yet soft quality in their decays that remained entirely distinct from low-end bass frequencies. Snare drums found the benefits of a low mid thump and center-high mid crack.



The IE 900 packs some clean highs that are broadly and smoothly boosted. The greatest beneficiary of this characteristic was vocals, which contained not only a clean airiness, but also found emphasis on their more intimate details such as tongue clicks and lip smacks. By some act of technical magic, the IE 900 pulls this off without any trace of harsh sibilants. This emphasized high end was, for me, an ideal complement to the boosted low end. The big-yet-controlled bodies of kick drums found further definition in their loudly emphasized transients that resided in the 3 – 5 kHz region. A lot of headphones and earphones that inject a bold boost in their highs are prone to rolling them off by 10kHz, but the IE 900 seems to keep chugging along well above even 12 kHz. This wide bandwidth boost allows the high end to retain a natural character that avoids steep ramp-ups and roll-offs, which are frequently responsible for artificial-sounding highs with awkward and noticeable cut-offs.

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Sennheiser’s IE 900 is a serious IEM. It’s industrial, brutalist look almost seems like a power move on the company’s part, as if there was no need to add dressing to something that sounds so clean and balanced. Needless to say, the IE 900 really is among one of my favorites in its price range. It offers the sort of clarity that can expose parts of mixes that I haven’t heard before – an elusive quality to any headphone or IEM that I treasure when I come across it. The Sennheiser IE 900 might have an intimidating price tag at $1,499, but if you’re looking for something that comes anywhere close to its quality for less, I wish you luck. Let me know if you find it.


The Sennheiser IE 900 is available here from Audio46.

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