Sennheiser IE 900 review: Aiming for the summit

Introduction, design, and features

Note: This review was first published on 19 August 2021 and it's republished now because it's still Sennheiser's flagship IEM and is still one of the best-sounding IEMs you can buy.

Behold the new flagship

Unlike phones, flagship IEMs don’t come around often. Sennheiser’s last flagship-class IEM, the IE 800 S, was released in 2017. So you can imagine the excitement the new IE 900 caused when it was announced earlier this year in May. The move is a concerted effort by Sennheiser to refresh its IEM lineup which started in January this year with the IE 300. On paper, the two have a lot in common, but as we all know, specs barely tell half the story especially when it concerns audio.

Design & features

The IE 900 and IE 300 share the same design which is no bad thing. The IE 300 was supremely comfortable to wear and the IE 900 is no different. Its fits snugly in my ears. And because it’s so small and light – a mere 4g – you barely notice it in your ears.

The main differences lie in where they are made and the materials. While the IE 300 is made in China, the IE 900 is made in Germany. It’s an important point of distinction, especially for enthusiasts, mainly because it costs S$1,999 and also because only Sennheiser’s most important and premium products are made in their German factories. 

On the materials side of things, while the IE 300 makes do with a hard plastic shell, the IE 900 features a milled aluminium housing. Each IE 900 shell starts off as a block of aluminium which is then precision-milled to create its unique shape. This step is particularly crucial because within the aluminium shells are three Helmholtz resonator chambers that were designed to minimise unwanted frequency peaks.

The shell feels bombproof. Milling leaves tell-tale lines and Sennheiser decided to embrace this by accentuating the milled lines on the shell. The final result, to my eyes at least, is quite aesthetically pleasing. The shells are also anodised so that they are resistant to wear and corrosion.

The IE 900 uses MMCX connectors. The connectors are specially designed so that they sit within a recessed socket so that there’s strain relief. This might causes compatibility problems with aftermarket cables so pay attention to fit if you intend to use your custom cables with the IE 900. Bundled with the earphones are three cables with 3.5mm, 2.5mm, and 4.4mm plugs so that owners can use their IE 900s with a wide range of balanced and unbalanced devices. These cables are made of para-aramid which Sennheiser says can withstand “many thousands of bend cycles”.

Sennheiser should be applauded for providing this many cables and the cables certainly feel strong and durable. However, they are also quite stiff. And this, coupled with the fact that they are coated in a TPU material, make them feel like rubber hoses. So as high quality as they may be, they don’t feel quite feel like premium items. The current trend is for high-end IEMs to come with braided Litz cables which are often soft and pliant and Sennheiser could definitely look to emulate that. 

Included with the additional cables are six additional pairs of ear tips – three pairs of memory foam ear tips and three pairs of silicone ear tips. The silicone ear tips feel smooth and soft but my preference is for the memory foam ones. They do a noticeably better job at blocking out unwanted ambient noise. Owners also get a sturdy carrying case that is emblazoned with the serial number of the earphones and has sufficient space for the IE 900 themselves and all the additional cables.