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Sennheiser IE 900 universal fit in-ear monitors

Sennheiser IE 900 universal fit in-ear monitors

As you may have read, Sennheiser’s search for a buyer for its high-profile, well-regarded yet not-all-that-profitable consumer audio division ended at the start of May 2021. The announcement that Swiss hearing care company Sonova Holding AG is now the proud owner of all that history, all that cachet and all those high-profile, well-regarded yet not-all-that-profitable soundbars, headphones and DACs came just ahead of the launch of these IE 900s – which makes them a product that signifies both the end of an era and a brave new beginning.

But new ground can only be broken once, right? In the world of consumer electronics in general and hi-fi equipment in particular, once that new ground has been broken, everything that comes afterwards is just a variation on a theme. And you’d be forgiven for thinking the good people in Sennheiser’s consumer audio departments might have bigger fish to fry right now than simply turning out a variation on a theme, no matter how impressive that variation might be. Anyway, on the face of it the biggest variation on the wired in-ear monitor theme the IE 900 represent revolves around their remarkably hefty asking price.

You’d be hard-pressed to come up with a consumer electronics category that’s currently less fashionable than wired in-ear headphones. ‘In-ear’ strongly suggests ‘portable’, and ‘portable’ is currently a euphemism for ‘wireless’. And let’s face it, ‘£1,099 per pair’ has never been all that fashionable where in-ear headphones of any configuration are concerned. So it seems reasonable to suggest the IE 900 are something of a niche product. But this is not to suggest Sennheiser hasn’t lavished the sort of attention on the IE 900 that has always made the company’s in-ear monitors such compelling propositions.

Even if considered simply as a feat of engineering, Sennheiser’s achievements with the IE 900 are significant. Each earpiece housing is milled (on five – count ‘em! – axes) from a single billet of aluminium – on the outside, this creates an interestingly contoured, jewelry-like appearance, while on the inside it means a triple-chamber absorption system. Dubbed ‘TC3A’, the system (which also features an acoustic vortex milled into the nozzle) is designed to counter the ‘masking’ effect that manifests itself at lower volumes. In simple terms, human hearing struggles to identify high-frequency sounds if lower-frequency sounds occur at the same time and at a higher volume – so the absorber system removes peaks of interference, allowing uncoloured reproduction of the frequency range even at modest volume levels. That’s the theory, anyhow.

Doing the sonic business inside each earpiece is the most recently fettled version of Sennheiser’s 7mm extra wide-band transducer. This new ‘X3R’ transducer, naturally enough, shoots for super-tight tolerances and class-leading fidelity – Sennheiser is claiming the lowest unit-to-unit variations ever achieved in miniature dynamic drivers such as this. The company uses precision cameras to monitor components during production, and tests the transducers before and after pairing. A claimed frequency response of 5Hz – 48kHz and THD of 0.05% at 94dB does rather hint at high-level performance. Many rival manufacturers like to incorporate a balanced armature or two in support of a dynamic driver when designing their own high-end in-ear monitors – but Sennheiser (not without justification) asserts that one driver to cover the entire frequency range, if properly implemented, represents the epitome of high performance.

To ensure this high-level performance is available no matter the source player into which the IE 900 are plugged, they’re supplied with a choice of connectors terminating with MMCX connectors. Take your pick from 3.5mm unbalanced, 2.5mm balanced or 4.4mm balanced – ideally you’ll be using one of the last two, plugged into a high-quality digital audio player. Because if you don’t have a nice DAP with unbalanced output(s), why are you spending a comfortable four figures on some high-performance in-ear monitors?

For the purposes of this test, the IE 900 are attached to a FiiO M11 Pro digital audio player via their 4.4mm balanced cable and to an EarMen TR-Amp headphone amplifier via their 3.5mm unbalanced alternative. The headphone amp itself is charged with turning the USB audio output of an Apple MacBook Air from a sow’s ear into a silk purse – and unlikely as it seems, the TR-AMp has pulled off this trick before.

It’s no mean feat to sound simultaneously wide open and tightly unified, but it’s this apparent dichotomy that’s the most immediately impressive aspect of the IE 900 sound. A hefty 24bit/192kHz file of The Band’s Across the Great Divide [Capitol] makes it absolutely plain: the Sennheisers create such a spacious soundstage that each individual element or strand of the recording is simple to locate, enjoys proper autonomy in its specific area, and has more than enough room to reveal even the finest or most transient details of its individual performance. But at the same time, there’s an unarguable sense of singularity about the way the IE 900 present this song – the impression of a group of musicians performing sympathetically, responding to each other and to the demands of the composition on the fly, is extremely strong. Very few headphones, no matter the price, can communicate the idea of musicians all bearing down on a piece of music with a commonality of purpose, but a free-flowing looseness at the same time, as these Sennheisers.

The same recording allows the IE 900 to showcase their talents where a smooth, even and utterly convincing description of the frequency range is concerned. Not many groups manage to make modern instrumentation sound as antiquated, whiskery and woody as The Band, and the Sennheisers are almost gratuitously detailed from the top of the frequency range to the bottom. Bass is full-figured but fleet of foot, with plenty of substance but next-to-nothing by way of overhang – control is absolute. At the opposite end, there’s absolutely as much bit and shine to treble sounds as is acceptable – but though they periodically threaten to spill over into harshness or shoutiness, it never quite happens and, instead, they offer some citric sharpness to the otherwise ‘down-home’ tonality The Band so relished.

It’s in the midrange, though, where the IE 900 are at their most prodigiously communicative. Detail levels are sky-high, and the line between forensic meticulousness and spontaneity of performance is walked with complete confidence. Listening to this song as an information-rich digital file via a pair of Sennheiser IE 900 is not unlike looking at a beautiful view through a freshly washed window.

And the story remains the same no matter the sort of music you care to listen to or how you may seek to find a weakness in the IE 900 game. They tear through Pere Ubu’s Non-Alignment Pact [Blank] with obvious relish, they are as soothing as they come with ((( 0 )))’s Nature’s Joint [The Sundrop Garden], they have the dynamic prowess and powers of rhythmic expression to make the heavily processed sound of Clinic’s 2nd Foot Stomp [Domino] sound almost organic.

Really, once you’ve managed to justify the outlay to yourself there are remarkably few downsides to Sennheiser IE 900 ownership. They’re light, comfortable, and Sennheiser has made a real effort with the way they are packaged and presented. Each cable resists the transmission of any kind of noise. The way the housings are milled, and the material from which they’re constructed, makes them look quite attractive in situ too.

Of course, when a piece of equipment has to be small and light by simple requirement of its function, it’s nigh-on impossible to make it look like a premium product (unless you just cover it in Swarovski crystals or something). And sure enough, no one is going to glance at you and your IE 900 in‑ear monitors and think “my goodness, they look expensive!”. But when you’re in the right spot – which is inside a pair of IE 900 – you’ll know exactly why they cost what they cost.



  • Type: in-ear
  • Drivers: 7mm dynamic driver
  • Frequency Response: 5Hz–48kHz
  • Impedance: 16 Ohms
  • Noise cancellation: none
  • Distortion: < 0.05% at 94dB/1kHz
  • Sensitivity: not quoted
  • Accessories: 6 × silicon/foam eartips; hard case; MMCX‑terminated 2.5mm, 3.5mm and 4.4mm cables
  • Weight: 4g
  • Price: £1,099


Manufacturer: Sennheiser

URL: en-uk.sennheiser.com


UK Distributor: Sennheiser

URL: en-uk.sennheiser.com

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