Koss ESP/950 electrostatic stereophones Page 3

The Kosses made their strongest impression in the all-important midrange. The adjective "palpable" is overused, but I don't know of a better term to describe the ESP/950's greatest strength. The human voice is particularly well treated—rich, full-bodied, yet without boxiness, nasality, shout, excess sibilance, or other unpleasant and unnatural colorations. From the close, intimate sound of Rickie Lee Jones's work on Pop Pop (Geffen GEFD-24426)—her first "audiophile" album, and which certainly sounds the part on the Kosses—to Kathleen Battle's gorgeous vocalizing on Baroque Duet (Sony SK 46672); from Richard Thompson's clear, rich voice on Rumor and Sigh (Capitol CDP 7 95713 2) to José Carreras's ringing lyric tenor on the now near-classic Misa Criolla (Philips 420 955-2), fans of all types of vocal music (among whom I definitely count myself) will be ecstatic over the sound of the Kosses.

The ESP/950 may, in fact, have been almost too forgiving in the midrange and high end. But again, never in a way which came across as dull or rolled-off. And recording sins, though sometimes more tolerable because of the Kosses' inherent smoothness, were nevertheless laid bare. The recording engineer who decided to throw a ton of artificial reverb over the voices in the new studio recording of The King and I (Philips 438 007-2) should have to spend eternity doing the same for Milli Vanilli: The Comeback Album. The damage was obvious through the ESP/950.

Soundstaging through headphones tends to be a sometime thing, and the newest Koss electrostatic is no exception. There is left, right, and in your head. This appears to be a fact of headphone-listening life. Of the various attempts to eliminate this effect, none, to my knowledge, has been fully effective. Part of the reason for this, of course, is that most stereo recordings have been made to be heard over loudspeakers, which require and create very different listening conditions. Even true binaural recordings (footnote 2), though they can produce a stunning illusion in many respects, and often provide a more believable soundstage through headphones than do conventional stereo recordings, have never provided this listener with a convincing illusion of a front-located performing group over any headphones I've heard. I have never heard as good a soundstage over headphones as I have with loudspeakers. It is no indictment of the Kosses to say that they do at least as well in this respect as any other headphones I have heard, without breaking the headphone-soundstaging barrier.

My reaction to the ESP/950's bottom end was a bit mixed. For the several weeks in which I listened to it as my sole headphone reference, I felt quite satisfied with its sound in this region. There was, on a significant number of recordings, a certain degree of warmth which I found generally unobjectionable. The upside of this was that the Kosses avoided any sense of sounding lean or analytic. If they sacrificed a bit of midbass clarity to achieve this, most listeners will not be at all upset with the result. It was hardly noticed until I compared the ESP/950 with the Stax Lambda Signatures.

The Stax comparison
When Bill Sommerwerck reviewed the SR-Lambda Signature T1 (footnote 3) headphones in Vol.11 No.8 (August 1988), he called them the best headphones around. He found them very revealing—perhaps too much so with bad program material for some listeners. My reaction was similar, though I wouldn't go so far as to call them ruthlessly revealing. The Staxes are open, airy, very transparent, and just slightly cool or lean through the bass and midbass, with an extended but not striking lower octave. I understand BS's mild criticism of a certain woolliness to the Signature's bass, but I would not make much of a point of it. I found its definition and clarity through the mid- and upper bass to be fine—in fact, that was the Lambda Signature's one point of distinct superiority over the Koss ESP/950. The latter was decidedly warmer in sound. Call it fuller and richer if you like this quality, darker and less detailed if you don't. Which is the more accurate? (I'll get to that shortly.)

Suffice it to say here that, with commercial recordings, I was torn between the sound of these two first-rate headphones. The greater warmth in the Kosses was never heavy or oppressive, always musically convincing. Their sound, on a wide range of good to excellent recordings, never failed to make a positive impression. It was never analytical or etched; the midrange was, as I've already stated, gorgeous; and the highs were simply there, neither obvious nor dulled.

The Stax Signatures, with their somewhat leaner, more open textures and airy, extended top end, came across as a bit more analytical than the Kosses, but also more revealing. I had the distinct feeling that the Staxes were telling me more of what was on the recording, but not always to the benefit of my musical pleasure. Still, they sounded very, very good in all the conventional parameters we use to gauge the subjective listening experience. The ESP/950 was not as open or as transparent (though hardly lacking in these qualities), yet in some ways engaged me more in the musical experience. Both headphones were strikingly open through the midrange, the Kosses being a bit more forward and immediate. I could live happily with either, secure in the knowledge that if headphones were my listening medium of choice (footnote 4), I could scarcely do better (footnote 5).

Is it real, or is it...
But which, you ask again, is more accurate? During the final stages of the evaluation period, I had a rare opportunity to sort this out. In November 1992 Stereophile was scheduled to record its next album with pianist Robert Silverman. This time we were doing the recording locally, with Robert Harley as recording engineer. The analog master would be made on our own slightly modified Ampex ATR-100 open-reel machine; the master for the CD release would be made on a DAT, using the Manley D/A converter. The venue had already been selected—a church in Albuquerque with particularly good acoustics.

Footnote 2: In binaural recording—a major topic all by itself—the mikes are placed the same distance apart as the human ears, with some sort of absorbent barrier—preferably a dummy head, complete with torso—in between. The only right way to record for headphone listening is binaurally. The best source of binaural recordings and information I know of is The Binaural Source (Box 1727, Ross, CA 94957, Fax (415) 457-9052), run by John Sunier of NPR's "Audiophile Audition" program.

Footnote 3: The T1 suffix indicates Stax's top version of this headphone, with their SRM-T1 tube headphone amplifier/interface.

Footnote 4: And I couldn't justify spending $2000 on headphones unless I chose to listen to them often, or domestic circumstances did not allow the use of good loudspeakers at their optimum playback level.

Footnote 5: A brief exposure to the Sennheiser Orpheus (HE/HEV90) headphone system indicated that it, too, is a major contender. While the Stax Signature was unavailable at the time for a direct comparison, the balance of the Orpheus was clearly closer to that of the later-auditioned Stax—cool and slightly analytical, but very clean and detailed—than to that of the warmer, sweeter-sounding Kosses. Of course, with the Sennheiser, dedication to headphones is demanded. There's the little matter of their $12,900 price, which does include a tube amp and integral D/A converter—the latter with drop-jaw styling right out of a 1930s Flash Gordon serial.

Koss Corporation
4129 N. Port Washington Ave.
Milwaukee, WI 53212
(414) 964-5000

ndimoff's picture

Another great news is that the electrostatic transducers of the Koss'es do not age. Bought my pair in April 1993 and they still sound as new. In comparison, the panels of my Martin Logan Aerius electrostatic speakers need to be replaced every 5-7 years.