Sennheiser IE 900 Earphone Review

Clean, Balanced Sound with a "Striking Affinity for Detail"

After a few years with little engagement, the renowned German audiophile company Sennheiser is seeking to reconnect with loyal customers and connect with new ones. With their entries in the IEM segment (the IE 300 and the flagship IE 900), they are targeting one demographic in particular: The so-called next-generation audiophile who is looking for high-fidelity portable audio. They want convenience without sacrificing sound quality. With the IE 900, Sennheiser has created a masterpiece of technical innovation driven by meticulous attention to detail and an uncompromising demand for perfection. According to Sennheiser, "The IE 900’s affinity for detail is striking. The clean and balanced sound signature stays honest to the original recording—even on tracks whose secrets you thought you had exhausted.” And that is the audiophile's holy grail, right? Finding hidden treasure in your music.


  • Clean, balanced sound

  • Excellent detail retrieval

  • Three cable options

  • Lightweight and easy to wear


  • Listeners who value convenience and sound quality

  • Audiophiles who want critical listening on the go

  • Music lovers who enjoy an emphasis on vocals

  • "Detail freaks"

Materials, Quality & Comfort

The IE 900 is a really comfortable IEM. I think everyone's ideal is to pop in an IEM and forget it's there -- and the IE 900 handily accomplishes this.

Constantly reaching up to adjust your IEM? Fuhgeddaboudit!

Discomfort from earpieces digging in? Fuhgeddaboudit!

In fact, comfort was paramount in the development of the IE 900. Here's what Sennheiser has to say:

"Working musicians rely on high-quality, form-fitting earphones known as personal monitoring systems. But we felt the privilege of enjoying perfect live sound should not be the exclusive right of the performers of the world. So, we took the comfort and secure fit of these professional solutions as inspiration for the IE 900. Now you can enjoy a fit and quality that rival that experienced by the artists who create your music."

My experience with the IE 900 was very positive in this regard. I wore them for hours with absolutely no discomfort. Their smaller size and the way they sat in my ear canal made me forget that I was wearing them.

Unlike the IE 300, which has plastic housing, the IE 900 has precision-milled aluminum housing that lends a high-end look without adding heft. At 4g, you have nothing to worry about! And the shells are on the smaller side as far as IEMs go, making them ideal for smaller or sensitive ears.

As far as cables, you get your choice of para-aramid reinforced cables with gold-plated MMCX connectors and plugs: balanced 2.5 mm and 4.4mm and single-ended 3.5 mm. Each termination is seated within a recessed, 4.8 mm-wide socket below the surface of the housing, providing strain relief. Flexible and adjustable ear hooks keep the earphones comfortably in place.

Included with the IE 900 are a selection of silicone and memory foam ear adapters in three sizes. They adapt to the natural shape of your ear for a tailored fit.

Driver Technology

Single Dynamic Driver

This isn't the place to get into the merits of single driver vs. multiple driver designs, so I'll just talk about the single-driver design of the IE 900. The IE 900 has a single dynamic driver, which Sennheiser says promises greater fidelity for listeners and eliminates phase issues and the resulting distortion in overlapping frequency bands. The deployment of a single, high-performance dynamic driver completely avoids the sonic obstacles introduced by alternative multi-driver arrays: phase incoherence and the subsequent distortion borne from the overlapping frequency bands of the driver-crossover mechanism.

“The X3R system enables the listener to hear more details in their music which is what audiophile listening is all about. The three resonator chambers smoothen the frequency response at high frequencies in the area from 6 to 10 kilohertz, reducing the so-called masking effect. This means that you can better hear frequencies above 11 kilohertz – the details. The challenge here is to perfectly balance the three chambers to get the correct response. You need to tune chamber by chamber and then make sure they are perfectly balanced together to achieve the correct frequency response. This process requires advanced acoustic engineering.”

Andre Michaelis, Sennheiser

X3R Transducer
Sennheiser's proprietary X3R transducer is a refined version of the company's 7mm TrueResponse transducer. The X3R system delivers a coherent, artifact-free "Sennheiser Sound" found in audiophile headphones up to 8 times larger! Sennheiser's X3R triple-chamber absorber technology (T3CA) is milled right into the solid aluminum housing of each earphone. With T3CA, three Helmholtz resonator chambers are precision drilled into the aluminum chassis of the IE 900 and placed between the diaphragm and the nozzle. These tiny channels eliminate resonance peaks which, in less advanced products, can color the sound signature and alter the feel of your music. In addition, a complex structure in the nozzle of each earphone — the Vortex — swirls acoustic energy in these frequency bands to smooth out peaks. The acoustic vortex maximizes acoustic friction so that excessive energy is scattered. According to Sennheiser, it is the tuning of the X3R systems resonator chambers that makes the IE 900 truly stand out and why it offers such exceptionally good high frequency translation. The result? You hear more detail. Additionally, a new membrane foil lends a high degree of inner dampening, ensuring minimized natural resonances and distortion.

Acoustic Back-Volume

Sennheiser's goal with the IE 900 was to achieve a high-quality, transparent sound with no distracting peaks or troughs. One thing this requires is clear separation between the low and middle frequencies. To ensure accuracy across this important frequency band, Sennheiser used what is known as an acoustic back-volume. It’s a small chamber within a chamber that Sennheiser tuned to manage the slope and amplitude of the base lift. The way the back-volume helps achieve such a clear and natural sound signature is by controlling the direction and overall volume of air as it moves through the transducer system. What you hear is a pleasantly disciplined bass and mid-range experience that is devoid of unpleasant resonances and listening fatigue.

Sound Quality

Review setup: The Roon Ready Element X headphone amp/DAC/music streamer by Matrix Audio and the SP1000 DAP from Astell&Kern. With an impedance of 16 Ohms and a sensitivity of 123dB, the IE 900 is easy to drive, including from your smartphone. That being said, we always recommend pairing your high-end headphones and IEMs with a headphone amp/DAC or DAP.


At first, I wondered how much different they could be from the IE300, given that they look so similar. Of course, I should know not to judge a book by its cover.

Connected to the Element X, I was immediately blown away by the incredibly clear and natural sound coming from the IE 900. I perceived the sound to be full and forward, but not aggressive. And the detail! I truly heard things in tracks I know well that I didn't know were there. The IE 900 really excels here. And did I mention vocals? If you're a vocal-holic like I am, you'll love the IE 900 for rich, clear, emotive vocals, both male and female. Natalie Merchant's sweet and strong voice tore through the IE 900 with incredible depth and emotion.

I listened to several tracks from Elton John's Captain Fantastic and the Brown Dirt Cowboy. Once again, vocals, vocals, vocals -- and details! On the strong "Better off Dead," the delicate tinkle of bells stayed as crisp and apparent as the strong percussion. On the title track, I enjoyed glorious bits of detail that I didn't know were there.

Treble on the IE 900 is definitely something to write home about. Lots of sparkle. Piano on several tracks sounded absolutely gorgeous. I listened to Rodrigo y Gabriela's rendition of "Stairway to Heaven" and was tickled by the sweetness of the violin and tantalized by the texture and pluck of the strings. The IE900 kept things tight and separated during the frenetic latter part of the song. Indeed, instrument separation is a real strong point for the IE900.

On another cover song, Leo Kottke and Mike Gordon's version of Fleetwood Mac's "Oh Well," I adored the crisp pops of sound. Leo Kottke does not have a pleasant or even good voice by any objective measure, but it's got a lot of grit and realism to it, and the IE 900 let it shine.

Soundstage on the IE 900 is intimate, with layers of sound and everything clearly delineated. I felt very much "in the music," which is a great place to be.

IE900 with the Astell&Kern SP2000

A&K players are on the analytical side. Paired with the A&K SP2000 portable DAP, the IE 900 achieved a new level of precision and clarity. Listening to some acoustic Elton John, I was blown away by the immediacy of the music. I truly felt as though he was sitting on a stool in front of me singing just to me. The depth and detail of the music was enormous. Next, I listened to "You're So Vain" for a taste of some female vocals. Carly Simon's voice was clear and strong, her "son of a gun" whisper at the beginning really capturing my attention. But what really got me was the visceral thump of that bass guitar at the beginning: tight, strong, and wonderfully defined.  


Sennheiser IE900

Sennheiser IE300

Shure SE846

The most immediate question you may have is how does the IE 900 compare to Sennheiser's other new IEM, the IE 300? With a flagship designation and about four times the price, the IE 900 should blow the IE 300 out of the water. The IE300 has a sound signature that mimics many consumer-oriented headphones and IEM. In other words, it's got a fun and musical sound. It's not bass heavy, and it doesn't have a particular emphasis on vocals, but it's a sound that works well with a variety of music. That being said, it's not an IEM you would reach for if you're into critical listening.

The IE 900, on the other hand, has a more detailed and balanced sound than the IE 300. This, to my ears, is the biggest differentiator, and the foremost reason one might opt to fork out the money for the flagship option. If you want a pair of IEMs from a venerable audio company that are going to give you that detailed, natural audiophile sound with no pretense, then the IE 900 would be your choice. With an upper end that extends to 48kHz -- far beyond the range of human hearing -- the IE 900 offers more air and detail and energy than its less expensive sibling. The IE 900 also features three as opposed to one resonator chamber, which accounts for the clearer sound of the IE 900. The IE 300 comes with one cable as opposed to three with the IE 900.

I also compared the IE 900 to the Shure SE846 Professional Sound Isolating Earphones, known for delivering extended high-end clarity and unparalleled low-end performance through quad high-definition drivers. Adjustable frequency response for customizable sound signatures with removable metal nozzle and changeable nozzle inserts (balanced, warm, and bright options included; I listened to the balanced mode). The SE846 to me was pretty neutral, maybe slightly warm, slightly less forward sounding, but with more bass presence. Vocals were pretty forward as with the IE 900. Highs are smooth and clear, though they don't have the same level of sparkle as the IE 900.

The Verdict

You know you've found a keeper of a headphone or IEM when you want to keep on listening to every single piece of music you know and love. This was my experience with the IE 900: a pleasure to listen to and super comfortable to boot. A nice, full sound that sounds natural and clear -- great with blues, folk, acoustic strings, and music with lots of detail. Vocals are super clear and emotive. If you're deciding between the IE 300 and the IE 900, choose the IE 300 if you want a fun sound for on-the-go listening, the IE 900 if you are all about detail and clarity and are not willing to compromise. You won't be disappointed.

Featured Products

Sennheiser IE 300

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Shure SE846 Isolating Earphones in Clear

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Sennheiser IE 900

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Astell&Kern SP2000 DAP Music Player

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What's in the Box

  • IE 900 in-ear headphones

  • Balanced para-aramid reinforced cable with 2.5mm connector

  • Unbalanced para-aramid reinforced cable with 3.5mm connector

  • Balanced para-aramid reinforced cable with 4.4mm connector

  • 3 pairs of silicone and 3 pairs of foam ear adapters (S, M, L)

  • Premium carry case with metal serial no. plate

  • Cable clip, cleaning tool & cleaning cloth

  • Presentation box with signed customer certificate & user manuals


Sennheiser IE900 IEMs Review

Sennheiser IE900 Unboxing


Technical Features

Transducer principle: Single dynamic driver, pressure chamber

Technology: X3R

Frequency Range: 5 Hz – 48,000 Hz (-10 dB)

Impedance: 16 Ohms

Sound pressure level (SPL): 123 dB (1 kHz, 1 Vrms

Max Input Power: 00mW

Total Harmonic Distortion (THD): <0.05% (94 dB, 1 kHz)


Housing: One-piece precision-milled aluminum housing

Cable length: 126 cm

Weight: 4g

Warranty: Global 2-year warranty

Connector: Fidelity (+) MMCX

Ear coupling: Ear canal