Sennheiser IE 900 IEM
To see a World in a Grain of Sand
And a Heaven in a Wild Flower
Hold Infinity in the palm of your hand
And Eternity in an hour.
—William Blake
Life has its external and internal manifestations. I think we all would agree the last two years have been an external manifestation no one wishes to repeat. But buried within these two years have been internal stories each of us carry and I, for one, expected this review to be finished and published a very long time ago. Such are the vicissitudes of life. But one unexpected benefit, a small silver lining, has been the extra time spent with the Sennheiser IE 900 IEM earphones ($1299). To the Sennheiser people and, particularly Shelby Coppola our distribution agent, who have been so generous and understanding in permitting me extra time with the IE 900, I say a very grateful—thank you! Now, let’s have a close look at the IE 900s.
The IE 900 is now the flagship IEM for Sennheiser. The venerable German audio company is not only going after their traditional and loyal customer base with the IE 900, but casting their net further afield for the ubiquitous new discerning customers who swim in the fiercely competitive IEM market, who love the highest fidelity possible in a convenient and portable IEM—and are willing to spend the coin to get it. At $1299, the IE 900s must be seen as a serious investment.
Construction and Technology
The IE 900s are small, light weight, conch-styled ear modules made of anodized aluminum, an electrolytic process that is a type of controlled oxidation of the original aluminum. This leaves an anodized layer three times harder than the original material; it will never rust, patina or weather. And because the anodic layer ‘grows’ directly from the original aluminum with no external paint or application applied, your IEMs will never chip, peel or flake. The IE 900s sit comfortably inside the ear opening allowing one to hear clearly without hiking the volume from your source beyond a rational level. My guess is the anodized one aluminum piece has created some of its own unique sonic differences over the ceramic-made earpiece of the less expensive IE 300s.
The IE 900s come with eartips which feature a foam filter and wave guide that can have a noticeable effect on your sound source; 3 cables, including the standard 3.5 millimeter and balanced 2.5 and 4.4 millimeter cables all connected to the MMCX connectors. All of this is beautifully packaged and presented by Sennheiser which adds a further layer of practical and aesthetic pleasure to the purchase of the these IEMs.
I’ll discuss the driver design in more detail in a moment, but the single dynamic driver approach to the IE 900 relieves the need for a complex electronic crossover sending different frequencies to multi-drivers, an engineering reality that can have less than ideal consequences depending upon the source you are plugged into. A single dynamic driver (see photo below) does not share this problem; in fact, the single dynamic driver allows for a wider range of frequencies, a generally more fulsome bass, and works with just about any source you wish to use.
Similar to the IE 300, Sennheiser’s earlier IEM, the IE 900s use a single dynamic driver per side, but with a new coil design. It’s worth pointing out single dynamic drivers are the most common driver type amongst Inner Ear Monitors. There are sound reasons for this. The single driver contains a tiny cone-shaped diaphragm connected to a coil of wire wrapped around a magnet, thereby magnetizing the coil. When an electric signal is initiated, the magnetic field causes the coil to move back and forth—hence the other appelation sometimes used, ‘moving coil driver.’ The diaphragm connected to the coil displaces the air around it and produces sound. The significant air displacement gives the driver an ample bass response. Another feature of the IE 900.
Unlike the earlier Sennheiser IE 800 that used two Hemholtz resonators to balance the treble, the IE 900s use three resonators per side. These absorber systems or resonators are milled from a solid block of aluminum to create a unique triple-chamber absorber system with an acoustic vortex milled into the nozzle. The milling process itself requires enormous precision that can only come from a CNC machine (photo below). After the milling process, everything is assembled by hand in Germany.
The triple chamber absorber design is created specifically to ameliorate the problem of ‘masking resonance’, the acoustical phenomena whereby the human ear cannot hear higher frequency sounds at a low volume when sounds in a lower frequency range are at higher volumes. Sennheiser, with the proprietary X3R transducer, a more refined version of their 7mmm audiophile Extra Wide Band transducer, and the unique triple chamber system already discussed, removes the energy from the undesired peaks, ensuring a brilliant and natural sounding upper frequency, especially over 6 kHz, with a heightened and sharpened sense of nuance and detail. The masking resonance and harshness are successfully removed from the sonic soundscape with this impressive new design.
Now, before we come to specific music examples, we should point out that the Sennheiser IE900s show frequency deviation from the Harman Curve and maybe, at this point, we should explain a little about this legendary frequency response curve and its history. Let’s be clear the Harman Curve is not the 10 Commandments from ‘on high’ but a consensus curve gleaned from hundreds of serious listeners of recorded music. Let me give you some background.
After decades of the audio industry dealing with the aptly named problem—the circle of confusion—Sean Olive and Todd Welti with Harman International undertook a series of seminal tests with trained listeners to find a consensus in timbre, spatial identity and frequency balance in recorded music with loudspeakers. They found a broad preference for speakers that measure flat with a smooth dispersion across all frequencies. They then set forth to replicate the results for headphones.
Easier said than done. The character of headphones as a sound source must take into account directional localization which entails four types of audio cues: head-related transfer function, interaural time difference, interaural phase difference and interaural level difference. I won’t bore you with a description of each cue but the take away should be your head, shoulders, ears and torso cumulatively contribute to the sound as an audio source which reverberates and bounces off these parts of your body. When you get to the pinna and canal of the human ear, you arrive at an extraordinary level of complexity in measuring time intervals between ears and so much more. Consider also, headphones cannot suggest room effects, that is, the natural reflection of sound and that sense of space that comes from loudspeakers cannot show up in headphones. Headphones are, however, a simple compact set-up, and can reduce noise intrusion and offer better low bass extension than some loudspeakers. I will spare you any further Biology 101, but the science behind the construction of a good headphone and IEM is very impressive.
The challenge was to use the Harman curve from the loudspeaker’s tests with the use of the GRAS 43AG, a standardized ear and cheek simulator, and two types of headphones—the ICD2 from Odyssey and the Sennheiser HD 518. Armed further with an equalizer, they established those measured frequency patterns many listeners found to their liking. Results were first published in 2013.
They found listeners divided into three groups. Those that loved headphones tuned close to the Harman curve were the majority; 64% of the listeners tested came from a broad spectrum of ages, the majority, however, 50 years and under. The second group, 15% of all listeners, were majority male and younger; they preferred headphones tuned 3 to 6 dB more bass than the Harman curve at sounds below 300HZ and 1dB more output above 1kHZ. We’ll call them the more bass group. The final group were disproportionately female, over 50, and their ideal was less bass. These folks occupied 21% of all listeners, preferring a 2 to 3 dB less bass than the Harman curve and 1 dB more output above 1kHz.
So, the Harman research showed not what listeners should like, but what the listeners actually liked. In their paper from 2014, a listening test involving 238 subjects in Canada, China, Germany, and the US, ranging in age from 20 to 70, the researchers found that ‘Listeners generally preferred the same headphones regardless of their listening experience, age, or country of residence.’
What do these targets suggest? The Harman Curve targets suggest a type of empirically derived basis for certain frequency distribution patterns amongst consumers. They also point to, in my opinion, certain psycho-acoustic principles that cannot be denied. That is, there is a quasi-objective dispersion of bass, midrange, and treble frequencies that most listeners respond to as good sound!
Disregarding the vexatious subwoofer and its exaggerated bass pattern for a moment, we are reassured, nevertheless, most serious music listeners want balance with small different preferences in varying frequency ranges. But it was the Harman research that established a possible target curve, not etched in granite, but as an intelligent guidepost. This is where our Sennheiser IE900s ($1299) fit in. Many headphones such as our Sennheiser IE900s will differ in some ways from the frequency targets of the Harman Curve—and that’s a good thing. For this offers a soundscape and a sculpturing of sound that will be unique. Even those headphones that match the Harman targets, the HiFiman Anandu and Sundara, the Sennheiser HD600, and the Focal Clear and Utopia, are different sounding Headphones. Long live diversity of sound.
Specifications
Transducer principle: dynamic, Extra Wide Band (XWB)
Transducer size: 7 mm
Frequency response (speaker0: 5 Hz - 48,000 Hz
Ear coupling: In-ear, closed
Sound pressure level (SPL): 123 dB (1 kHz, 1 Vrms)
Total harmonic distortion (THD): < 0.05% (1 kHz, 94 dB)
Cable length: 1.25 m
Connectors: stereo jack plug, gold-plated, MMCX plug
Impedance: 18 Ω
Attenuation: -10 dB
Sound
Let’s test drive these babies. All my listening examples flowed through Apple Music from my computer into my Mytek HiFi Manhattan DAC II (the unit includes a headphone amplifier and preamplifier).
Ernest Ranglin’s Below the Bassline album, and highlighting the last track of the same name, one cannot help be impressed with the clear layering of textures you hear. The clear low C in the double bass doubled at the octave by the Gibson f-hole hollow body electric Gibson guitar of the legendary Jamaican guitar player Ernest Ranglin with the scintillating and shining short metal splash of the high-hat from the percussionist, are brilliantly reproduced by the Sennheisers. From the piano and its off beat chord structure to the engaging Wes Montgomery octave solo from Ernest, the IE900s capture mid-range and bass sounds with perfect clarity.
To give the Sennheisers a further workout in the bass area, I put on Cream’s ‘Badge’ from Goodbye, and sat back to listen to Jack Bruce’s extraordinary tasteful and memorable musical bass line. This composition was written by Clapton and George Harrison and the piece is enhanced—an understatement—by Bruce’s bass work; the sound and the texture of his bass playing are captured perfecty by the IE900s. There is no ‘flatulence’ here in the mid-bass to lower bass range—the IE900s reproduce Bruce’s bass playing with near perfect amount of decay that was evident in his original playing and with that rhythmic ‘lift’ and bounce that was Bruce’s style.
Speaking of rhythmic ‘lift’, if we continue with one more ‘pop’ example of a superb bass part to showcase, it is Chic’s ‘Good Times’ on their 1979 Atlantic Record release Risqué. If you’re short of time, fast forward to the 3 minute and 21 second mark and behold the dance-like funk bass solo played with rhythmic and technical precision by Bernard Edwards and with Nile Rogers’ rhythm guitar entering around the 4 minute mark. Both men were producers of this track. Again, no ‘flatulence’, no dampening bloom to the sound, but a clear transparent window to the authentic decay of his bass sound. By the way, ‘Good Times’ is an example of delicious irony presented in pop culture, oh so rarely, but often understood later, as a disguised trope on contemporary events. 1979, the year of the recording, was also the Iran embassy disaster, the OPEC monopoly’s increase in oil prices, line-ups at gas stations in the US, Three Mile Island nuclear reactor meltdown and a massive recession with stagflation as its viral load. In other words, a huge shit-storm and Nile Rogers and Bernard Edwards laid down one of the last disco hits speaking of Good Times. You’ve got to love it.
Eugene Ormandy with the Philadelphia Orchestra playing the final movement of Saint-Saëns’ Symphony No. 3, the Organ Symphony, his majesterial final symphony that brought the symphonic technique of thematic variation developed by his close friend, Franz Liszt, to a brilliant culmination, is our next example. Saint-Saëns finished his work stating, ‘I gave everything I was able to give. What I have accomplished here, I will never achieve again.’ We want to point out the bass acuity of our Sennheiser IE900 as we listen to the organ entry in the final movement of the symphony—the accelerando peroration to the symphony where the organist plays the descending C major scale arriving at the speaker rumbling infamous low C in a triumphant ending in C major. (The IE 900's frequency range is stated as 5 Hz to 48 kHz, so it exceeds the Hi-Res designation by a full 8 kHz. The low pedal C of cathedral organs has been measured at 16Hz. Please remember, this also exceeds the average human's hearing range of 20 Hz to 20 kHz.)
What I love about Ormandy’s recording is how forthright the organ pedal notes are. Anyone who knows this ending is aware of the absolute fire and tumult Saint-Saëns has written for the orchestra whilst the organ descends. When you consider most of the performances of the Organ Symphony are recorded in spacious and cathedral-like settings—the added resonance and reverberation from such enormous spaces can be quite muddying—the Sennheisers do an amazing job of separating the instruments whilst exciting fire and brimstone descending organ passages.
Anne Sophie von Otter recorded an album with Elvis Costello, titled For the Stars, in 2001, containing pop tunes written by Elvis Costello, Lennon-McCartney, Brian Wilson, Anderson-Ulvaeus and Svante Henryson on the Deutsche Grammophon label. ‘Baby Plays Around’, co-written by Costello and his ex-wife Cait O'Riorda, has Elvis on keyboard, Bengt Forsberg on Hammond organ, Mats Schubert on piano and the stunning and the wonderful flugelhorn soloist at the end of the piece, Pat White. ‘Baby Plays Around’ offers a classically-trained mezzo-soprano an exquisite pop piece of pathos that brings you in close with her voice, as if she is whispering into your ear—as if she is confiding in you. The IE900s offer a super clear instrument separation again and utterly convincing imaging. Ms. Otter’s voice is clearly in another world from her role as the Marschallin in Der Rosenkavalier, but it is the intimacy of her performance that is arresting here and her voice has a foreground presence that is superbly represented by the IE900s. The soundstage is wide and the conclusion of the piece by the flugelhorn solo is a haunting layer to a first-class piece of pop music.
One penultimate quick note and that is the beginning of Steely Dan’s ‘Do it Again’ from Can’t Buy a Thrill. The Sennheiser’s once again show a superb separation of sounds of the opening percussion instruments and just before the vocalist begins, there is the sound of glass tinkling—it is a magical and ephemeral moment, beautifully separated and memorable.
Summary
My verdict is in. The Sennheiser IE 900 is a formidable and incomparable IEM offering the best and cleanest bass and imaging sounds in the marketplace. The engineering changes that I spoke of earlier in the review have proven themselves a superior addition to the august Sennheiser line of IEMs and headphones. The IE 900 brings forth more detail and significant sparkle to the upper frequencies than any other IEM of which I am aware; acoustic instruments come alive and imaging within the very wide soundstage is vibrant and vivacious in colour and balance. You could say that these Inner Ear Monitors push the limits of treble energy, yet without any harshness and with a degree of detailed refinement. And clearly the addition of the three Helmholtz resonators do sculpt the treble response to remove the problem of masking resonances, thereby ensuring the mid-range frequencies are forward and detailed. Combine this overall sound with a taut and clear bass range and you have a winner, pure and simple.
The opening stanza of William Blake’s To See a World, the opening to this review, speaks of seeing the Universal in the temporal detail of this world, and I, for one, know in our search for a metaphor we are always listening for the small inner workings and detail in music, yet never losing sight of the wholeness of its construction. The Sennheiser IE 900s ($1299) deliver just that—amazing detail within the balanced wholeness of the music. You can’t ask for much more, and, in closing, I would, once again, like to thank Sennheiser and Shelby for their patience and latitude in permitting me such time with the Sennheiser IE 900. Without reservation, I am happy to award the Audiophilia Star to this outstanding product.
Further information: Sennheiser
