|
|
Home | High-End Audio Reviews | Audiophile Shows | Partner Mags | Hi-Fi / Music News |
|
 
|
29 Years Of Service To Music Lovers |
|
|
|
High-Performance Audio Reviews
|
|
September / October 2003
AKG K1000 Headphones
High performance headphones have a special role in the history of high fidelity. The first brand that sold on the basis of its sound quality was Koss with models the Pro 4AA, a head cruncher with oil foiled ear cushions and an insipid sound quality which boasted, as I recall, of being capable of covering 'all ten audible octaves'. It took a much cheaper model from an upstart European microphone manufacturer - Sennheiser - to show how it should be done when they strung two open-back microphone capsules together with a hoop of plastic, and sat them on the ear with cushioning discs of reticulated foam. The headband was near indestructible, and the cables could be plugged out and replaced when the connectors broke, which they did reliably and often. But it was not their serviceability that attracted buyers in previously unprecedented numbers, nor was it just the low price. It was their previously unmatched sound quality, which was open, detailed and transparent.
By contemporary standards, the HD414 is still just about presentable, but it is also thin and bright. The state of the art has moved on. But in certain respects headphone design hasn't altered a lot over the years. Tiny in-rear phones of the kind introduced by Sony and popularized by the rise of the personal stereo can be shockingly good, one of the few real innovations since the HD414 was new, though there tends to be little bass or image scale, and no real distance in the sound. Everything seems to happen by direct injection into the ear canal, and of course this exactly reflects reality. To a lesser but still dominant extent, this is what still applies to most headphones if we leave aside those that are simply incompetent. Nevertheless, there has been a persistent strand in headphone design which has sought to overcome the problems that are endemic with headphones. These problems are usually perceived as centering on the inability to achieve a realistic stereo image. Headphone sound does indeed tend to be very 'in head', and usually fails to breathe properly, though conversely clarity and transparency tend to be very strong. Coloration is another problems. Rarely mentioned in the context of headphones generally, I would contend it is a very real problem that tends to be exaggerated by the close coupling between the transducer and the ear. Most of the causes of coloration are related to the structure of the headpieces, either through energy storage, or reflections from hard surfaces, and they tend to be particularly obvious in practice. With loudspeakers there are many ways for comparable colorations to be diffused and neutered.
Various names are associated with the high points in headphone design. Sennheiser deserves mention with its early and mid period designs, along with Beyer and AKG, but it was Stax that set the highest standards, albeit at high prices, with their range of exactingly engineered and costly electrostatics One in particular, the SR-Sigma, was notable for its acoustic design which placed the transducer well away from the ear, and angled forward of the ear plane and facing backwards, the idea being to mimic the layout of a pair of stereo loudspeakers. Jecklin took a slightly different approach with their Float designs. They did not repeat the angled forward geometry of the Stax SR-Sigma, but they were designed to be supported clear of the ears to provide some natural space and 'air' to the sound, and to reduce structure borne
colorations. For this reason the AKG is not pre-wired with a headphone plug. In fact the first 6 feet or so of wiring downstream of the phones themselves is a fairly conventional thin, pliable cable much as you'd expect to find with many headphones, except that a male locking 4-pin XLR socket terminates it. The rest of the wiring - a full 10 feet of the stuff - is rather thicker oxygen free stock with a transparent cover, equipped with a matching female XLR at the upstream end, and four bare wires at he other for hard wiring to the loudspeaker terminals. The arrangement is hardly elegant, but it is functional enough. The XLR connectors design is as rugged as they come. The headphones themselves are slightly less oddball looking the enormous Jecklins or the Stax SR-Sigma, which look at though you're wearing a couple of boxes. They look initially like straightforward low profile phones, except that the only parts to bear directly on the head are the headband, a standard two part design with an outer steel hoop to define the inwards pressure with a self-adjusting inner leather hoop for location, and a pair of horizontal leather covered bars that locate just above each ear on the temples. This arrangement holds the earpieces clear of the ears, Jecklin Float fashion, but the K1000 has another trick up its sleeve as the earpieces are attached to the headband by a vertical pivot which allow the earpieces to be rotated out at the back so that they fire from a diagonally forward position into the ears. In effect it mimics the dispersion of the Stax SR-Sigma, but without the supporting (and inevitably reflective) superstructure. By this means, AKG have aimed to address the issues concerning true binaural perception, which relies on differential time delays for sounds arriving from off centre positions, and on spectral differences produced by the 'shadowing' effect of the ear's pinna geometry when immersed in a soundfield. The first is generally regarded as the most important factor, and means that the ear hears the nearest sound first, which the ear locates in space using the precedence effect (the real picture is rather more complicated because the precedence effect is frequency dependant). But it is the differences due to pinna geometry and the effect this has on the spectral response above about 2kHz that AKG claim is responsible for creating a fully three dimensional out-of-the-head listening experience. A key design priority was to ensure a degree of intra-aural crosstalk, and the open construction of the K1000 helps ensure that each ear hears the time delayed output of the opposite channel at about -30dB or -40dB, which is within the -50dB limits required for binaural perception. The angle of the earpiece relative to the ears is an important factor in producing the appropriate (ie natural sounding) spectral response, but so is the presence of reflections from the structure of the headphones themselves, which the designer has done everything possible to control. Look carefully at each earpiece and you will see that even within the wire mesh frame, construction is as open as can be contrived. The drive unit rare earth magnet has the smallest possible surface area, and the unit itself is suspended from the corners of the earpiece, so that there is only a very limited area of reflecting surfaces. The driver has a high power handling ability, partly because the aluminum coil former acts as a heatsink in its own right. An electronic tuned circuit helps tune the acoustic response of the system, and transient response was also a design priority.
Sound Quality In particular, the K1000 probably won't appeal to those looking for a headphone with the sophistication of a Stax electrostatic. It is polished and neutral, but it doesn't have the same kind of finesse or the exquisite detailing as the best electrostatics. In particular the treble doesn't have that very special brand of sweetness or sharp precision, though it is more than usually detailed by moving coil standards, and the treble is well integrated and fee of obvious colorations or excess. But the K1000 has something that even electrostatics don't usually have. There is a visceral quality to its sound, almost as though the sound can be reached out and touched. The soundstage has all the qualities that are implicit in the idea of good binaural reproduction, that is realistic perspectives and scale to accompany the good left/right differentiation that all headphones produce as a matter of course. But there is less artifice here. The soundstaging is much more natural than you might expect, and central images don't collapse into a spot in the middle of the head, though it takes a suspension of disbelief to place the soundstage forward of the plane of the ears. Perhaps this is a personal reaction too, or the result of having listened to too many headphones over the years. What is certain however it that the K1000 sounds more musically direct and dynamic than you might expect of headphones. Not that other models are generally incapable of going loud and soft. What the AKG can do however is to remain consistent sounding over a wide volume range, which means that the dynamics of the music breathe in a convincing way. This kind of consistency doesn't always happen with the reproduced article. The bass is good but not outstanding. More correctly, it is not particularly full, but it is deep and well extended, and it is extremely tuneful and well integrated. At this end of the spectrum the lack of coloration is particularly impressive, not because it is any lower than the midband or treble coloration levels in absolute terms, but because other headphones almost always sound much more colored at low frequencies, either deliberately for effect, or because the designer has not learned how to control the structure of the headphones. Running through the last few discs played on my digital roundabout, Toru Takemitsu's How Slow The Wind (Kioi Sinfonietta Tokyo conducted by Tadaaki Otaka on the BIS label) is simply exquisite, like a handful of scattered jewels on a black surface intermittently reflecting light when irradiated by a passing spotlight. A recording of one of the Bach Cantatas (BWV105, Bach Collegium Japan, also on BIS) has a wonderfully rapt quality, each voice distinct from the others, yet the whole blending in together homogenously when required. A recording of the Shostakovich Leningrad symphony (Gergiev/Kirov & Rotterdam PO on a Philips SACD) worked wonderfully, with an anguished yet impressively powerful sound which is particularly impressive when the earpieces are opened out a little wider than usual, and the volume increased to what feels like a realistic level. But the K1000's qualities are by no means restricted to a narrow band of music types. The seductive quality of Eve Cassidy's Kathy's Song is unmistakable, while the breathy vocals on Mining for Gold on Cowboy Junkies The Trinity Session sends a shiver down the spine. This kind of performance, consistently displayed with a wide range of music genres, is quite special, and marks the K1000 out from its peers.
Comfort There has been some discussion in the media about the quality of the cables, with various recommendations for replacement for the cable part downstream of the XLR, which is physically very easy to replace. I was not able to locate any appropriate cables that are on sale in the UK in time for this review, but I would offer a word of caution about this approach, which really requires that the complete wiring be replaced, not just the conveniently accessible final ten feet. As resolution rather than power handling is the key requirement. I would be interested in hearing a version of the K1000 rewired with one of the Nordost cable range, but this would be an inordinately expensive undertaking, and I'm not aware that it has been tried elsewhere. In any case, dismantling the earpieces is quite likely to result in damage and would certainly invalidate any warranty.
Conclusion
Specifications Impedance: 120 Ohms Sensitivity: 74dB for 1mW free field Frequency Response: 30Hz to 25kHz Power Requirement : 100mW for 1Pa
Distortion at 400mW: around 100dB Power Rating: 1000mW (test tone DIN 45582) corresponds to approx 104dB Headband: force exerted on 140mm wide head 3.5N (DIN 45580) Weight: 270g without cord, 370g with cord and connector Test Conditions: free space Accessories Supplied: wooden case, 10-foot extension lead. Price: $700 (approximate "street price")
Company Information Voice: +43 1 86654-0
United States Distributor Voice: (615) 620-3800 |
Binaural microphone recording techniques were developed soon after, first demonstrated as I recall by Sennheiser themselves with a specially recorded 7 inch EP which when played back through open back phones like the HD414s opened a window on an unmistakably real acoustic space. I remember hearing this disc at some hi-fi show, and practically jumping out of my skin when I heard the announcer's voice just behind my right ear.
|
