Koss ESP/950 electrostatic stereophones TJN returned to the Koss in February 1994

TJN returned to the Koss in February 1994 (Vol.17 No.2):

I was able to compare the Stax Pro Classic with both the Sennheiser HD-580 driven by the matching HeadRoom Supreme headphone amplifier and the Koss ESP/950 electrostatics. When I reviewed the latter last year (Vol.15 No.12, p.158), I was captivated by its midrange performance, but I didn't think its response at the frequency extremes was quite up to the accuracy of the $2000 Stax Lambda Pro Signature. The Pro Signature's balance isn't much different from that of the Pro Classic, save for the Signature's more refined top end.

Compared to the Koss, the Pro Classic had a decidedly leaner, more analytical sound. The Koss's bass was richer and more full-bodied, though it didn't seem to extend any deeper than the Pro's. The midbass of the Pro Classic was tighter and had greater clarity, but at the expense of leanness—most evident on solo instruments and voices. I can think of no headphones, and few loudspeakers, that are as compelling through the all-important midrange as the Koss was. The treble forwardness and slight top-end fizz I heard from the Pro Classic were nowhere to be found with the Koss, though the Stax had a more sparkling top octave and an arresting sense of detail. In terms of perspective, the Koss was more forward and immediate, though not pushy, aggressive, or hard.

Perhaps because of either this or the Stax's physical design, the Koss had a bit more of that "in-your-head" imaging quality. The more distant sound of the Stax, while not able to replicate the frontal soundstage of loudspeakers, did come closer to that more natural perspective. I'm inclined to favor the Koss's sound over the Stax's, largely because of the former's midrange qualities and the latter's more overt top end. But the Stax's openness and clarity can't be ignored.—Thomas J. Norton

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.