Sennheiser IE 900

Sennheiser IE 900 cabled earphones – hear things you have never heard before (review)


The Sennheiser IE 900 are audiophile-grade earphones. So, we don’t even have to whisper that they cost $2099, and they rely on good old fashioned German audiophile engineering – not psychoacoustic trickery and app EQ to deliver beautiful sound.

And beautiful sound it is. I must remember to thank Thomas Bartlett (our former resident audiophile) for passing the baton to me – an amaterphile – who is a fast learner. When you enter the audiophile world, it is like identifying the grape, vineyard, year and slope it is grown on – in wine terms anyway. Well, I am trying.

For me, every audiophile experience gets better. Hi-res DACs, headphones, earphones, music and a greater understanding of why my Bluetooth headphones and earphones (while they sound good) are inferior. And to a degree, my understanding that less is more – especially in the cost department.

If $2099 is a little more than your budget/partner allows, Sennheiser has an IE 300 for $479.95 (GadgetGuy review here 9.4/10) and the IE 800 S for $1599.95, both of which at least gets the subtle ‘S’ logo into your ears.

Sennheiser IE 900 cabled earphones

FromSennheiser, Addicted to Audio and other audiophile outlets
Warranty2-years ACL
Country of manufactureDesigned and made by hand in Germany
AboutSennheiser is a German company. Although established over 75 years ago, its first product was a voltmeter, but it soon began making microphones and headphones. It is now owned by Swiss-based Sonova
MoreYou can read more GadgetGuy Sennheiser news and reviews here

First impressions

$2,099 for two tiny little aluminium ‘buds’. I have not felt this intimidated since someone threw me the keys to a million-dollar Lamborghini to take for a spin – and no, I was not a parking valet! And yes, I did – it is a brilliant beast that took my breath away.

There is enormous responsibility here – audiophiles can be so picky. So if you wish to comment, please do so, and we can both learn.


Once you unpack the tiny buds, you choose small, medium, and large silicone or Visco memory foam ear tips. The latter provides the best noise isolation, but you tend to feel them more in your ears. I settled in silicone for comfort.

Next, you have the choice of three stereo jack connectors to MMCX connectors. These are reinforced with para-aramid for outstanding stability even after thousands of bend cycles. And at the MMXC end, have flexible sections you can bend back over your ears. The 1.25m cables include:

  • 2.5mm balanced signal, 4-pin
  • 3.5mm unbalanced signal 3-pin
  • 4.4mm balanced signal 5-pin

Fit and comfort

They fit inside your outer ear with just the cable arching back over the ear. If the cable was not so short (1.25m), you could probably wear them to bed.

I wore them for a total of 10 hours (8 hours plus 2 x 1-hour walks), and there was no discomfort. I preface that by saying the silicone ear tips are more comfortable at the expense of some noise isolation. Sennheiser claims -26dB noise isolation – our tests agree.

To DAC or not to DAC

I can’t tell you to rip out and buy a headphone DAC, but I can tell you that there is a world of difference using the Astell&Kern USB-C DAC (review 9/10) to play hi-res music* on both a Surface Pro 7 and a Samsung Galaxy S21 Ultra.

The DAC has a frequency response of 20Hz-20kHz at .0004THD and will support up to 32-bit/384kHz, so it is not holding the IE 900 back. Three things were most noticeable with the DAC

  • The volume is excellent on the Surface Pro 3.5mm jack but vastly louder with the DAC.
  • Sounds were there that I had never heard before, even in Sennheiser’s best Momentum 3 BT headphones
  • The broad sound stage and left/right separation is incredible

* Hi-res came initially from YouTube Music in AAC 256kbps, but we swapped to Amazon in FLAC 24-bit/192kHz. Tidal seems to have a better catalogue and offers MQA, AAX, ALAC and FLAC in 24-bit/192khz. Other sources include QoBuz, Spotify, Apple Music and Deezer.

When playing CD-quality MP3, the DAC bought out the best in the rip. As the IE 900 has no EQ or app, what you put in is what you get out.

How does the Sennheiser IE 900 sound?

Across the board, it brings out sounds and nuances you will never have heard with BT headphones. It neither adds to nor subtracts from the music, although the detail it reveals in standard-definition Spotify is palpable. It is like playing music on a smart speaker and casting it to a proper Sonos or Bose speaker. You can never go back.

Note that the Samsung S21 Ultra (Exynos CPU) with a standard USB-C to 3.5mm cable (a Google Pixel 4a cable) is not as good as expected. I blame the cable. But the Astell&Kern DAC, while very good, did not have the same sparkle as via the Surface Pro 7. I tried with an OPPO Find X3 Pro (SD888), and the sound is considerably cleaner.

Sennheiser IE 900 specs

  • 7mm XR3 transducers with 5Hz-48kHz – nice but overkill
  • Impedance 18 Ω (works from 2 Ω or more)
  • SPL: 123dB at 1kHz
  • THD: .05% 1kHz 94dB
  • Wight: earphone bud each 4g and 24g with cable
  • Presentation box with carry case, cleaning tools and more

Sennheiser is proud of the audio achievement that comes from each bud individually milled from a block of aluminium and precision matched. Its XR3 tech includes:

Specially developed membrane foil and acoustic back volume, triple-chamber absorber system and acoustic vortex for an intense listening experience. What refines the X3R technology is its three Helmholtz resonator chambers and acoustic vortex, which smoothens masking resonance. The three resonator chambers are precision-drilled into the elegant aluminium chassis of the IE 900 and placed between the diaphragm and the nozzle

GadgetGuy’s take

The Sennheiser IE 900 deliver in-ear, studio monitor quality in a portable bud that you can use every day. MP3 rips come alive, and hi-res music is spectacular. No, it has no fancy tech – no app, EQ, synthetic music, mics, noise-cancelling. It is what the musician wants you to hear.

How it achieves 5-48kHz with a single transducer is a testament to Sennheiser audio mastery. The answer is quite simply the three Helmholtz chambers tuned to specific frequencies. But one caveat – GIGO – garbage in means garbage out. Good quality music deserves these earphones.

Would I buy these?

My wife, upon learning the IE 900 were $2,099 legitimately asked what the target market was. We deduced that a) you had a means to depreciate these off tax immediately (business purchase) or b) if I was an audiophile with plenty of money, then yes – of course. Remember they are in-ear monitors (IEM) and have a specific target market.

Joe and Jane Average want wireless Bluetooth convenience, so the best you can get is the Sennheiser Momentum True Wireless 2 (review here 9.5/10) at $399.95 on special. These offer open-backed sound quality and a lovely wide sound stage without overpowering ANC (it has excellent ANC but not at the expense of music quality).

Sennheiser IE 900 cabled earphones
The Sennheiser IE 900 are audiophile-grade earphones. They rely on good old fashioned German audiophile engineering – not psychoacoustic trickery to deliver beautiful sound.
Value for money
Ease of use
Pure sound as the musician intended it
Replaceable cables and ear tips if needed
Beautiful packaging
A tad expensive but if you are an audiophile - who cares?
Needs hi-res music to justify it
Needs a decent DAC to use with a PC or USB-C smartphone