Shure KSE1200

If you thought earbuds were a compromise, think again...

We all like to listen to music on the move, and many of us also appreciate the benefits of in-ear monitoring when performing. Both applications require high-quality earphones, and the market is awash with wired and Bluetooth designs at prices ranging from under a tenner to several thousand poundsdollars.

Shure are one of the most respected and familiar manufacturers of earphones, with their own range of sound-isolating models starting at under £50 (for the SE112GR), and extending up to nearly £900 for the SE846. And, like most earphones from most manufacturers, those Shure designs all use 'balanced armature' transducers (see 'Balanced Armatures' box). However, not all manufacturers choose to use balanced armatures. For example, Sennheiser applied its considerable expertise in moving-coil headphone drivers to develop a miniaturised version just 7mm in diameter, for use in their top-of-the-line IE800 earphones, which I reviewed a few years ago — see www.soundonsound.com/reviews/sennheiser-ie800.

Static Conversion

Another sophisticated transducer technology that's occasionally used for high-end loudspeakers and headphones is the electrostatic transducer. This works a bit like a capacitor microphone in reverse: an incredibly light but strong plastic film carrying a static-electric charge is suspended between a pair of conductive grilles. When a high AC voltage (carrying the audio signal) is applied across the grilles, the film is attracted and repulsed by the changing electric charges, and by moving back and forth it acts as a diaphragm to reproduce the acoustic audio signal.

One of the advantages of this technology is that the diaphragm is virtually mass-less — it certainly weighs less than the air surrounding it, unlike a moving-coil transducer design — so it has negligible inertia and can respond virtually instantly to the subtlest nuances within a signal. It's also inherently driven across its entire surface to act as a true piston, and can reproduce the entire audio bandwidth, so there's no need for multiple drivers. Moreover, there are no inherent resonances or energy storage artifacts in the diaphragm, the transient response is incredibly accurate, and the transducer's harmonic distortion is typically an order of magnitude lower than that of an equivalent-sized moving-coil device at mid and high frequencies, and two orders better in the lowest octaves. In short, there is (currently) no better method of reproducing sound!

The obvious question, then, is why hasn't this technology already taken over the monitor speaker and headphone market? Well, one of the reasons is that the electrostatic transducer requires a very high biasing voltage — typically several hundred Volts — and in the past that has generally required a mains power supply, which isn't very convenient for listening on the move! Modern electronics have solved that problem, though. In the case of loudspeakers it is also difficult to generate higher SPLs, especially at low frequencies, although that's not really a problem for headphones. Perhaps the strongest impediment is the inherently high cost of manufacture, due to the fine production tolerances and precision construction that is required.

Shure Thing

Despite all the challenges, though, and after eight years of development, Shure created the world's first (and currently only) electrostatic earphone, the KSE1500, a couple of years ago. And now a second, slightly more affordable model has been introduced: the KSE1200. Both use the same earphones, and the difference between them relates only to the amplifier pack and its facilities. Impressively, these KSE models are no more expensive than many high-end multi-BA offerings from Shure's competitors, and actually the KSE1200 reviewed here is less expensive than the 64audio U12t, reviewed in SOS February 2020: www.soundonsound.com/reviews/64-audio-u12t.

The KSE1200 is presented in a soft-finish black cardboard box with shiny black writing — this kind of packaging seems de rigueur for expensive hardware these days! The thick 74-page user guide looked imposing, but it's a modern Rosetta Stone with only five pages allocated to describe how to use the system in each language — and two of those pages just carry the obligatory legal warnings and certifications!

A dedicated amplifier module (more below) sits in the presentation box alongside a tough zipped carry–case to store the earphones, adaptor cables and spare earbuds (but not the amplifier). Hidden under the earphones, which are presented neatly in a foam cradle, is a cardboard box containing sets of 'soft-flex' rubber, soft-foam, and triple-flange earbud sleeves, each of which come in three different sizes. A wire-loop cleaning tool is also included.

As always with earphones, the external sound isolation and low–frequency response is entirely dependent on how well the sleeves fit the listener's own ear canals, so having such a comprehensive range of options is very helpful. Shure claim external sound isolation can reach 37dB with well-fitting earbuds, and I don't doubt it. Note that there is no noise-cancelling technology here; this is purely mechanical sound isolation.

I'd have to say these are the most transparent and natural-sounding earphones I've ever heard.

Whereas ordinary earphones are plugged directly into the music source, these electrostatic earphones require a dedicated high-voltage amplifier to bias the transducer diaphragms. The KSE1200's amplifier is housed in a nicely machined black aluminium case with dimensions of 59 x 93 x 21 mm (WHD). For such a compact unit it's surprisingly heavy, at 155g, largely due to a large Lithium-ion battery pack. This can be recharged via a USB micro-B socket in the base from any standard USB port (a USB‑A to micro-B cable is included), and a full charge provides around 12 hours of listening.

The flagship KSE1500 model's amplifier module is about 1cm taller to incorporate a small OLED menu screen and an internal D‑A converter which accepts a digital audio signal via its USB port. However, the KSE1200 reviewed here is an analogue-only device, and its USB connection only provides the charging functionality. A slide switch on the base next to the USB socket engages a 10dB input pad, which could be useful when connecting high-level analogue sources.

Topping the amplifier are two sockets, two LEDs, and a semi-recessed rotary volume control. Both status LEDs are tri-colour, with one indicating the audio input level with the usual traffic-light scheme while the other shows battery status (green for on, amber for charging and red for low battery). The unit is turned on or off by rotating the volume control, which has a switch function at the counter-clockwise end.

A 3.5mm socket accepts an unbalanced stereo analogue input, and both 6-inch and 36-inch mini-jack cables are included to hook up to a music source. There's also a 3.5mm socket to quarter-inch plug adaptor for connecting to full-sized headphone outputs. Both of the supplied cables have straight plugs at both ends, but I much prefer to use right-angle plugs as I've found that straight plugs, when pulled sideways as they so often are, exert leverage onto the socket's contact springs, bending them and eventually causing poor and intermittent connections. Right-angled plugs simply rotate under tension and are far more reliable, in my experience.

In-ear Peace

The earphones connect via a miniature LEMO socket which sticks up a good 50mm from the top of the amplifier. The cable length seems to assume the amplifier will be pocketed, but although a couple of wide rubber 'amp security' bands are provided (presumably to minimise case scratching), Shure don't supply a belt hook or pouch, which seems a bit stingy given the price of the system. A leather pouch with belt loop is available as an accessory for around $45!

Given the 200V biasing voltage employed here, the custom-designed cables running into each earphone are a little thicker than normal due to additional insulation around each conductor. Nevertheless, the cables are still very flexible and the usual sliding 'cable cinch' can be used to hold them securely at the back of the head. A crocodile clip is also included to attach the cable to clothing, if required.

The earpieces themselves are pleasingly slim and lightweight at just 44g, and are actually pretty much the same size and shape as most conventional Shure earphones. The electrostatic transducer modules are encased in transparent bodies (although there's nothing interesting to see), and the cable entries have the usual stiffened sections which can be shaped tightly behind each ear. The acoustic output nozzles are the same size as all other Shure earphones so standard sleeves fit and, as I've been using SE315s for years as my cheap travel earphones, I simply swapped my own preferred soft rubber sleeves directly across to the KSE1200s to start listening.

As with many other Shure models, the earpieces are identified with coloured dots (blue for left and red for right) and inserting the earpieces requires the same simple technique as other Shure models. I found the fit comfortably snug and secure, and I could shake my head and jump about without any fear of losing the earpieces. External noise was also highly attenuated — I'd estimate over 30dB — across the full bandwidth.

For a music source, I connected the amplifier to the headphone output of my Crookwood mastering console and, with the amplifier volume turned right down, I adjusted the Crookwood output level to get a steady green light on the level meter with no ambers. I selected a playlist of my usual speaker demo tracks and carefully advanced the volume control...

Ecstatic

Up to this point, inserting the KSE1200s felt much the same as my old SE315s, but as I advanced the volume control I discovered a weird psychological connection to my jaw: the more I advanced the volume, the more my jaw dropped!

I've listened to quite a few expensive, elaborate and high-end earphones, but these Shure KSE1200s really raise the bar further than I thought possible. Like very good monitor speakers, the sound isn't 'instantly impressive' at all, but careful listening quickly reveals just how well balanced, and how revealing, these earphones are. The bass extension and linearity are astonishing; the specs claim a bandwidth of 10Hz to 50kHz and I was certainly hearing fundamentals below 20Hz on suitable test tones and other audio material. A sweep-tone from 5Hz up to 22kHz provided a flat, consistent and seamless response across the entire bandwidth — at least from the 15Hz to 17kHz range I can hear! Few multi-BA earphones have ever managed that!

The specs also claim a maximum SPL of 113dB, at which point the total harmonic distortion reaches 3 percent (it may sound a lot, but it's really not in the context of loudspeakers!). I'm afraid that wasn't something I wanted to test, but it was clear that the amplifier was capable of going way louder than I would ever need — I rarely had the volume control more than halfway. At sensible listening levels transducer distortion was utterly inaudible, even with complex multi-tonal sources; but more than that, I'd have to say these are the most transparent and natural-sounding earphones I've ever heard.

I've listened to quite a few expensive, elaborate and high-end earphones, but these Shure KSE1200s really raise the bar further than I thought possible.

Transients have a wonderfully precise snap and attack. Bass is deep, powerful and tightly controlled. And the high end is deliciously open and airy. More importantly, mid–range clarity and focus is outstanding, and musical dynamics are really brought to life with the quietest nuances revealed as easily as the loudest transients. Stereo imaging is also solid and stable, too, with binaural sources delivering a very realistic soundscape, and I found the cables transmitted almost no mechanical noise at all along to the earpieces.

A benefit of the ultra-low distortion and neutral transparency is that I was happily listening to the KSE1200s for much longer periods than I can normally tolerate most earphones, something that only the Sennheiser IE800s have matched, although I found the Shures more comfortable and secure to wear.

In conclusion, the KSE1200s are exceptionally transparent and detailed earphones, with perfect balance, extension and resolution, and I've certainly not heard anything else as capable or competent.