Sennheiser IE 300 earphones

Only just out is the latest Sennheiser ear-gear: its premium wired earbuds. I’ve chosen to call the Sennheiser IE 300 earphones IEMs or in-ear monitors. The model name implies it and they perform the function rather well, being way better than your typical earbuds.


  • 7mm XWB dynamic drivers, built in Germany, with resonator chambers to “remove masking resonances”
  • Impedance: 16 ohms
  • Sensitivity: 106dB for 1mW @ 1kHz (calculated from Sennheiser specification of 124dB for 1Vrms @ 1kHz)
  • Frequency response: 6 to 20,000 hertz
  • THD: less than 0.08% for 94dB SPL @ 1kHz
  • Earpieces weigh 4 grams each
  • Detachable, replaceable 1.25m cable using modified gold-plated MMCX connectors – not compatible with standard MMCX -fitted cables
  • Para-aramid fibre cable reinforcement
  • Adjustable ear hooks
  • Three sizes of silicone ear tips, three sizes of memory foam ear tips
  • Price: $479.95
  • Available at fine high fidelity retail outlets, and direct from distributor's retail division here
  • Good solid bass, a largely even tonal balance, with perhaps a slight boost in the lower treble that sometimes added a touch of pizzazz, sometimes a slight tinniness to the snare drum. But most importantly, these really are audiophile earphones, delivering that characteristic sense of openness, detail and presence in the sound.
Sennheiser IE 300 earphones

    A bit more about the Sennheiser IE 300 in-ear monitors

    The Sennheiser IE 300 IEMs seem aimed pretty firmly at portable use, what with their shortish cable and 3.5mm gold-plated plug and a neat, zippable carry case.

    While the Sennheiser IE 300 IEMs are “Made in China”, the XWB – “Extra Wide Band” 7mm dynamic drivers are made in Germany. Sennheiser has engineer what it calls “resonator chambers” in the body of each earbud. Contra the name, these are apparently designed to “remove masking resonances”.

    The cable at the earphones end is terminated by gold-plated MMCX connectors, the standard for this application. The last few centimetres of cable are encased in earhooks. This isn’t unusual for this kind of application, but what is a little unusual is that you can form them into a shape which will be retained.

    See the specifications above for the raw numbers. I should note that I calculated the sensitivity figure of 106dB for 1mW. Sennheiser frequently specifies sensitivity for 1 volt RMS at 1kHz. That makes it difficult to compare with other headphones, since most makers use the one milliwatt measure. On the assumption that Sennheiser’s 16 ohms impedance rating is also for 1kHz (a very safe assumption it turns out, as we’ll see), I worked out the power output at 1Vrms – 62.5 watts – and how many more decibels that is than 1mW – 18dB. Take 18dB from 124dB and you have 106dB. Comparing with other headphones and earphones, that seemed about right.

    Sennheiser IE 300 earphones with scale

    An impressively flat impedance curve

    Since we’re talking numbers, I’ll toss in the one measurement I conducted here. That is a proxy for impedance across the full audio band width. A wide variation means that the earphones would not be suitable for use with headphone outputs with a high impedance of their own. See here for why. One significant surprise for me was the Sennheiser IE 300 IEMs showed a very even impedance across the full audible frequency range. The graph shows the variation in the signal an amplifier with 470 ohms inline would deliver to them. As you can see, there’s only about half a decibel in variation from 20 hertz to 20kHz. It seems that you can uses these IEMs with pretty much any source.

    Sennheiser IE 300 earphones graph

    My listening will commence shortly. I had initially planned on expanding my range of listening modes by also trying out the IE 300 IEMs with a Brainwavz balanced cable I have, with a 2.5mm TRRS on one end and MMCX plugs on the other end. I’ve used the Brainwavz successfully with other earphones, including the Final Audio B3, but I could not get the Sennheiser earpieces to snap into the connection in a secure way. Going to Sennheiser’s website reveals that the MMCX sockets are “seated each within a recessed, 4.8mm-wide socket beneath the housing's surface.” This, says Sennheiser, “yields outstanding strain relief and stability, providing users with the utmost confidence that their IE 300 will always be ready to perform.”

    Cable protection is an important design consideration, and I’m glad Sennheiser is serious about it. Back in the days when all my in-ears were wired, I used to go through them about once each eight months due to cable failure.

    Still, it is disappointing can’t use other brands, unless some are made specifically for these earphones. Fortunately, Sennheiser is about to release balanced cables itself, one with 2.5mm TRRS termination, suitable for the bulk of quality digital audio players, and one with 4.4mm TRRRS, which is increasingly becoming the connection of choice for balanced headphones.

    I’ve got a request in with Sennheiser for these cables, and I’ll update this review once I have them.


    The first impression was a good solid bass, a largely even tonal balance, with perhaps a slight boost in the lower treble that sometimes added a touch of pizzazz, sometimes a slight tinniness to the snare drum.

    But most importantly, these really are audiophile earphones, delivering that characteristic sense of openness, detail and presence in the sound.

    Let me expand on some of this.

    I started my listening with the single-ended 3.5mm cable plugged into a digital audio player. Throughout I used memory foam tips. I used to prefer silicone tips, but over time I’ve come to appreciate the better seal available from memory foam. This provides greater isolation from environmental sounds and improves bass performance. I scrunch them into thin cones an instant before popping them into my ears, holding them in place for a few seconds as they attempt to resume their former shapes, instead moulding themselves neatly into my ears. The only downside with foam, in my view, is a slight worry about its longevity. I’ll just have to wait for that to become clear.

    Sennheiser IE 300 earphones

    Roxy Music’s Greatest Hits happened to be occupying the playlist of the DAP so I hit “Play”. “Jealous Guy” opened with a nicely solid kick drum and clearly articulated bass guitar line. The Sennheiser IE 300 earphones sounded big. And to my ears the balance really was very good. I’d found the earlier wired Sennheiser Momentum in-ears too bright overall. (I’ve noticed a trend with Sennheiser over the past few years. It seems to be pulling away from the unrealistically bright sound apparent even in such high-end models as the HD 820. Thankfully.)

    As I mentioned, there was that occasional splashiness on things like snare drums, and perhaps on the crash cymbal. But even that was only slight. The result was tuneful balanced music that I could listen to for hours without fatigue.

    I got into bit of a Roxy Music jag and went on to the 1975 album Siren. The drive in “Love is the Drug” was effortlessly delivered with neither the earphones nor the player taxed by the fairly high playback level. “Sentimental Fool” opens, as is Roxy Music’s occasional wont, with an unusual soundscape that gradually develops into a powerful song. When the drum kit comes in after about two and a half minutes, it was both welcome and sounded wonderfully solid. There was a little sibilance in Bryan Ferry’s singing at points during the climactic last minute or so.

    Out and about

    The Sennheiser IE 300 earphones are both nicely isolating and ridiculously revealing. As I’m writing this bit I’m sitting at the patio of my local coffee shop playing Ricochet by Tangerine Dream – the DSD64 version. The memory foam tips are keeping all the extraneous noise down to inaudible levels whenever the music is anything more than a whisper. The tonal balance is excellent – no harsh-miked vocals here – and the broad, almost three-dimensional soundstage produced by the mixing effects have the electronic sounds appearing from all over, sliding through space from place to place. And it’s all there, every element is complete and I can focus on one of the quieter background elements, follow it without it being submerged by the other material.

    Moving on to Glenn Gould’s 1981 re-recording of The Goldberg Variations (his first recording in the mid-1950s was smash hit … imagine, J.S. Bach a smash hit!) on CBS, the opening aria was sweeter-sounding than is usually the case. I confess that I had it up a little higher in volume that I would typically. Gould, always an enthusiast for the latest studio technology, clearly decided to make use of the 96dB dynamic range available from the then fairly new 16-bit digital recording technology. So when the first variation kicked in, it was way louder, really pumping out the decibels. The character of the Sennheiser IE 300 earphones did not change in the slightest – apart from the higher volume level.

    Sennheiser IE 300 earphones

    And even during some of the louder bits, it was possible to pick out Gould’s unfortunate vocal accompaniment.

    The just-about-acoustic Once I Was an Eagle from Laura Marling was nicely rounded. I feared that the vocal sibilance in the opening track might be overdone, but it was pretty much in the normal range.

    The DAP I was using can deliver 0.89 volts into 16-ohm loads without clipping. That’s a little over 50mW, or 17dB above earphone sensitivity rating – which works out to around 123dB with the Sennheiser IE 300 earphones. I don’t doubt it, although neither did I try pushing it that far.

    I also gave them a whirl with the AudioQuest DragonFly Red portable DAC which can manage only 0.45 volts output into that load, which is less than 19mW or 12.7dB. Again, not the slightest problem pushing these earphones to uncomfortably loud levels.


    Sennheiser has done a remarkable job with the IE 300 earphones. Yes, you can find even better sound out there in IEMs, but I think you’re generally going to have to pay quite a bit more for it than the cost of these ones.

    One final word: be cautious if you’re going to use these earphone out in the real world when they’re fitted with the memory foam tips. The noise isolation really is excellent. And you don’t want to be run over by an unheard bus.

    In-ear earphonesSennheiser