Sennheiser IE 900 in-ear headphone review: Sweet isolation

Price When Reviewed

$1,499.95

Best Prices Today: Sennheiser IE 900

Sennheiser has engineered its flagship IE 900 in-ear monitors for comfortable long-term wear and to sound fantastic. That’s it. They’re wired, and there are no in-line controls. There’s no active noise cancellation. There’s no microphone for phone calls. The IE 900 is a headphone designed for maximum audio quality, period. And Sennheiser delivers in that department.

At this price, why choose an in-ear monitor instead of on-ear or over-ear headphone? If you’re on the move, the IE 900 are sufficiently well-built to use as a commuter headphone and the case will fit in your pocket. If you’re in the office, your co-workers won’t be commenting on your giant pair of cans.

Ultimately, however, the IE 900 offer an immersive and intimate listening experience that’s different than anything you’ll get with an over-ear headphone. That’s not to say that one experience is superior to the other, but Sennheiser provides a wonderful contrast to an over-ear listening experience.

This review is part of TechHive’s in-depth coverage of the best headphones.

What’s the technology behind the IE 900?

James Barber/Foundry

Each earbud is milled from a single block of aluminum. Before we get to the audio advantages of this design, it’s worth mentioning how great they look and how fantastic their ridged design feels in your hand. There are a lot of excellent in-ear monitors made from plastic, but the metal construction of the IE 900 gives this headphone the feel of a true luxury product.

Beyond that, Sennheiser says aluminum is a key component in its triple-chamber absorber (T3CA) system. T3CA uses three chambers and an acoustic vortex milled into the nozzle to counter the masking resonances that diminish high-frequency sounds at lower volumes. The IE 900 also use Sennheiser’s proprietary X3R transducer, an upgraded version of the company’s 7mm Extra Wide Band transducer.

Sennheiser also touts a new membrane foil designed to provide a high degree of inner dampening, ensuring minimized natural resonances and distortion (THD: 0.05% at 94 dB, 1 kHz). The IE 900 have a frequency response of 5Hz – 48kHz.

The important takeaway from all those technical details is that Sennheiser uses a single driver in each earphone, instead of dual or triple drivers. A single driver eliminates the need for a crossover, which reduces distortion. Ideally, a well-designed single driver will deliver a tighter and more cohesive listening experience, and that’s certainly what the IE 900 delivers.

What’s included with the IE 900 in-ear monitors?

James Barber/Foundry

When you’re in this price range for a headphone, you expect a premium experience that starts at the unboxing stage. Inside the retail packaging, there’s a matte black box with a glossy Sennheiser logo printed onto it. Slide the inner box out and each earphone is nested in foam.

Beneath the foam, you’ll find a signed certificate of authenticity with a manufacturing date and a thick user manual in 19 languages. This might seem like overkill, but it’s exactly the kind of presentation that’s expected in the luxury goods market, and Sennheiser needs to sell a few of these to the price-is-the-object crowd to justify their existence and thereby subsidize the IE 900 for the pure audiophile crowd.

The premium presentation continues with a sturdy nylon carrying case that comes with a metal Sennheiser logo on the top and a metal plate glued to the bottom. That plate features your IE 900 serial number.

James Barber/Foundry

On a more practical level, the box includes three pairs of silicone ear adapters (S, M, L) and three pairs of memory foam ear adapters (S, M, L). I got a perfect fit from the silicone adapters. Sennheiser warns that the foam adapters have a limited lifespan and should be replaced after a few months.

There’s a cleaning cloth to keep your aluminum earphones shiny, and a cable clip if you want to attach your cables to your shirt. There’s also a cleaning tool to get the inevitable buildup of gunk out of your adapters and the earphones themselves. That tool is just a plastic handle with a thin loop of wire on the end to do the dirty work. Can you buy a cleaning kit on Amazon for just a few bucks? Sure, but the fact that Sennheiser chose to include one reinforces the overall premium experience.

Sennheiser includes three 49-inch para-aramid-reinforced cables for the IE 90: unbalanced with a 3.5mm connector, balanced with a 2.5mm connector, and balanced with a 4.4mm connector. Each cable is thicker at the end that connects to each earphone, and the cables loop over each of your ears, to reduce strain.

James Barber/Foundry

Sennheiser’s Fidelity Plus MMCX connector has a satisfying click when attaching to each earphone. The right earphone is labeled with a red band at the connection point, while the cables are embossed with a tiny L and R to indicate which earphone they pair with. This is a tiny complaint, but a similar red band on the cable to match the one on the earphone would be a huge help for anyone with less-than-perfect eyesight.

What does the Sennheiser IE 900 sound like?

I tested the Sennheiser IE 900 three ways: I used an Naim Uniti Atom HE amplifier, DAC and streamer; a Questyle M15 DAC connected to an iPhone 13 Pro Max; and a Lightning adapter connected to that same iPhone.

Because the IE 900 offers extremely effective passive noise cancellation with a proper fit, the experience of using them is decidedly different than the one you’ll get with a great pair of open-back or closed-back over-ear audiophile headphones. No matter how immersive the experience from a headphone like the Focal Celestee, the sense of isolation can’t compare to what you’re getting with the IE 900 in your ears. There’s genuinely a sense of being cut off from the world around you.

As word of jazz saxophonist Pharoah Sanders’ death hit the news, I decided to revisit his 2021 late-career masterpiece Promises, a collaboration with British artist Floating Points (a/k/a producer Sam Shepherd) and the London Symphony Orchestra. I listened to a Qobuz 24-bit/44.1kHz stream from my iPhone using the Questyle M15 DAC.

James Barber/Foundry

It’s a fascinating mix, one that puts Sanders’ saxophone front and center at the beginning and slowly brings Shepherd’s parts and the string arrangements to more prominent placements in the mix over the course of the LP.

The album’s nine tracks are variations on a single musical theme, built around Sanders’ playing and a brief interlude of his wordless singing in “Movement 4.” This is an album that rewards close listening and much of its impact comes from the shifts in volume and instrument placement in the mix. The IE 900 headphone creates the illusion that the music exists inside your head instead of coming from a great pair of speakers or headphones.

Promises also sounds incredible through my Focal Celestee closed-back headphone, but the IE 900 deliver a sense of immersion that the Celestee can’t quite match.

Turning to the 1979 album London Calling, by The Clash, I listened to a Qobuz stream of the 24-bit/96kHz remastered version via the Naim Uniti Atom HE. London Calling is the album where drummer Topper Headon and bassist Paul Simonon truly clicked into the rhythm section that elevated the band far beyond its punk roots.

On an album celebrated for its songwriting and Mick Jones’ guitar parts, the IE 900 reveals just how much the bass and drum parts contribute to the success of the album. That inspired me to move on to 1980’s Sandinista (also a Qobuz 24-bit/96kHz remaster) to check out songs like “The Magnificent Seven,” “Junco Partner,” “The Crooked Beat,” and “The Call Up” that demonstrate the band’s growing fascination with Jamaican dub.

What you get with the IE 900 is an accurate representation of the low-end action without any of the annoying bass-forward tuning that so many headphones employ. The IE 900 proved to be a remarkably versatile headphone. If you have broad tastes in music, they’ll handle most anything you want to play.

James Barber/Foundry

Not everyone will enjoy the isolated experience the IE 900 provide. If you’re in the same room with another person, you won’t be able to hold a conversation or click a control button to pause them. Even when the music is paused, you won’t hear much of what’s going on around you.

There’s one other caveat. When using the IE 900 with the Naim Uniti Atom, there was a bit of cable noise if I moved away from a stationary position. I didn’t have any issues with noise when using them with my phone, so it may have been more of a function of how the Sennheiser cable fit with the Naim headphone jack. The cable-noise situation is not an uncommon issue with high-end headphones, so I didn’t consider it to be a big negative, but first-time buyers in this price range should be aware that this kind of thing happens.

Is the Sennheiser IE 900 worth $1,500?

If you’re a casual music listener who’s not particularly focused on what you’re playing, there are dozens of wired and wireless in-ear options that will get the job done at a far lower cost. That’s not the market that Sennheiser is pursuing with the IE 900.

If you’re interested in the immersive experience offered by the best high-res audio and can pair the IE 900 with a DAC that can decode that higher-quality stream, Sennheiser has delivered an in-ear headphone that produces audio quality that can compete with high-end over-ear headphones in this price range. Even if you skip the DAC, the IE 900 offers a significant upgrade to standard in-ears with only a Lightning or USB-C adapter. With the Sennheiser IE 900, travelers can leave their bulky cans at home and enjoy an audiophile-quality listening experience in an easy-to-carry package.