Sennheiser IE 900 In-ear Headphones Review

Posted on 24th June, 2021

Sennheiser IE 900 In-ear Headphones Review

Matthew Jens samples some high-end headphones with a price tag to match…


IE 900 In-Ear Headphones

AUD $2,099.95 RRP

Listen, I love budget-friendly headphones. It's easy to appreciate when a brand puts research into creating the most value for every dollar spent and cutting costs by trimming the fat. I especially like it because occasionally, this process leads to giant-killers – affordable David designs that rival the headphone world's top dollar Goliaths.

Yet sometimes the high-end brands come back swinging, with no-holds-barred, top tier contenders for the top dog product, with no corners being cut at all. What happens when the Goliath strikes back? You can imagine my excitement then when I finally laid hands on the new IE900 in-ear monitors from Sennheiser. Years of research, dedicated development and German engineering have finally created a top dollar in-ear masterpiece for those bold enough to spend the mega dollars to acquire it. No giant killing here – this product sets out to be the giant to which prospective challengers can only dream of being compared.

So we have a range-topping flagship IEM, created by the boffins at Sennheiser with a seemingly limitless research and development budget. In a market looking to favour more budget-friendly and wireless options, is there a place for a product such as this? Superficially at least, the answer is yes. The beautiful enclosures, for example, are precision cut from a single block of aluminium using a five-way CNC router. They have several Helmholtz resonators milled directly into their inner shell. The path that takes the sound from the driver to the earpiece is a precision-built audio maze designed to smooth out peaks and bring out the frequency response specified by the company's engineers.

I asked Sennheiser about these clever acoustic chambers and if they were coming to any future products:

We implemented the resonator chamber technology for the first time in the IE 800 in 2012. Three years later, we used the same concept for the HD 800 S, which has been the reference for open headphones since then. The same transducer/resonator chamber concept is also used in the HD 820, which has extremely clear treble for closed headphones. We think the Helmholtz Resonator is a fantastic tool to fine tune a headphone to our exact requirements, so you can expect to see it in future products as well.

The TrueResponse 7mm drivers have also been tuned and matched during the design and manufacturing process to ensure there are no variances between units. I was delighted to find three different cables included, as well – one with a standard 3.5mm connector, one with a 4.4mm balanced connection, and a little balanced 2.5mm fellow as well. All feature gold plated 'Fidelity' connectors, para-aramid reinforced cabling and adjustable ear hooks, which get the job done. 

It's hard to ignore the microphonic noise that is transmitted through these cables with every tap and touch, though. I hate to sound nit-picky, but this is tricky to overlook in a top tier, no-holds-barred product. Despite this, the cables are comfortable, light, and don't remember how you twist and bend them. You'll easily fit one cable (with the IEMs attached) into the hard zip-case, which also has a serial number plate on it. It also doesn't eat up too much bag space and will comfortably fit into jean pockets.

The enclosures themselves are so small and light that physically popping them into your ears is effortless. Just poke them in, wrap the cables around your ears, and you're good to go. However, getting optimal sound with enclosures this small requires a bit of fiddling to ensure you get it just right. But once you've done it a few times, you'll get the hang of it, and muscle memory will take over; but there is a slight learning curve to achieving the right fit. 

Thankfully, Sennheiser has included many tips (six pairs in total) to simplify this fit process, including memory foam and standard olive tips. Interestingly, I usually wear medium tips but found that even large olive tips were ever-so-slightly small for me. Being a single 7mm driver with 16 ohm impedance, finding the right source to make these puppies sing isn't too demanding a task. Mind you, using a high quality dedicated DAP or something else with low impedance will benefit you here.


The IE900 surprised me when it came to sound quality. Or should I say that I was surprised by the fact that I wasn't surprised? After reading all the fanfare and documentation about the science and research that went into these, I knew full well that I was about to behold a transparent, analytical and enjoyable listening experience. 

If you get an opportunity to try these, my advice is not to limit your experience solely to jazz or orchestral music – as the IE900 has so much more to offer. Take Left Alone by Flume, for example. With its long-winded and detailed layers being added on top of one another throughout the song, the IE900 could pick these apart and let the samples play simultaneously in harmony, with a delicate cohesion. Unfortunately, down low, there wasn't quite enough impact to make this song shine the way it truly needs. Still, there was plenty of bass quality, detail and reach hidden underneath the gentle, wavering beat. 

Don't get caught out thinking the low-end response is too thin, however. There's enough bass presence and detail to cause Tom Waits' scratchy voice make your hairs stand on end. The delicate bass plucks in Coney Island Baby are reproduced with plenty of body and decay, and they don't for one second detract from the faded piano or violin. Or even from that vinyl crackle that plays underneath this whole song. Funnily enough, I've been familiar with this track for years and never noticed this until I had an intimate listening session with the IE900 and an Apple Music hi-res version of this song.

It was then time for a drastic change of pace as I moved to the violent stylings of the Doom soundtrack. Rather than this being a gentle listen, it would rather beat you over the head with an unwavering, unfaltering parade of metal music, hiding details behind the heaviest of heavy. The IE900 effortlessly reproduced the heavy percussion, aggressive guitars and the rest of the amusing stuff. It then caught its breath exceptionally quickly when the music abruptly stopped mid-song, releasing subtle details before slamming back into action at a shockingly quick pace. These tracks are great for testing dynamic range and decay, as they go from extremely loud to near silent in a heartbeat. The IE900 chased after these tracks like an excited pit bull, always right on pace and keeping up perfectly, with no muddiness or smearing. 

Honestly, the detail and high-end response here remind me of the Westone 3, ten odd years ago. This is a compliment, as back then many considered them to be some of the best IEMs ever created. Despite not having as much bass as a meathead like me might prefer, the reach, detail, air, and overall musical enjoyment are palpable here and keep me coming back for more every listen.

Last but not least, the IE900 is also a superb choice for content playback on something such as an iPad Pro. Paired with the humble Apple headphone adapter, the transient capability of the TrueResponse drivers, paired with the lightweight of these units, leads to comfortable and immersive marathon movie sessions.


What we have here, then, is a steep asking price for an incredibly detailed, airy, lean, clinical music listening experience, and Sennheiser's IE900 is a premium-priced masterpiece. 

This release is a shining example of why you should buy wired IEMs because while Bluetooth headphones are catching up to their wired cousins, they're just not there yet - and may never be. Nevertheless, the IE900 sits proudly on the throne, and if you're in the market for a flagship in-ear design with wires, then you really should give this is a listen. 

For more information visit Sennheiser


    Matthew Jens's avatar

    Matthew Jens

    Constantly keeping himself busy, Matthew is a production manager, Brazilian jiu-jitsu blue belt, Head-Fi fanatic, coffee enthusiast and all-round cool Dad.

    Posted in:Headphones Applause Awards 2021 Headphones In Ear Monitors
    Tags: sennheiser 


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