Background
My recent electrostatic headphone purchases are not my first foray into electrostatic headphones, not by a long shot. I was an early adopter of the Koss ESP/6 electrostatic headphones many decades ago, back in 1968. Yes, they were heavy and uncomfortable, with considerable clamping force. And they had their problems due to their "self-energizing" feature which used the audio signal to polarize the electrostatic elements. This caused the sensitivity of the phones to vary considerably with classical music which had long periods of quiet playing. This was something the factory seemed unable to correct despite my sending them back a few times. But when they were "on," they undoubtedly sounded better in important ways, such as clarity and audible detail without added brightness, than any other headphones I'd ever experienced.
The 1971 ESP/9 was better-yet sounding and did not suffer from the varying sensitivity problem. Removing the self-energizing feature from the headphones themselves to a black box helped the weight and reduced or eliminated the varying sensitivity problem. They were still heavy, however, and the clamping force was just as considerable.
When the various Stax electrostatic earspeakers became available a few decades ago, I listened periodically at audio dealers. The Stax were and are very light by comparison, had low clamping pressure, much larger earcups, and were, of course, open-backed, unlike the early Koss products. Yes, they were yet clearer sounding than those Koss models, but at least part of this was due to the fact that they always seemed bass light and treble strident to me, not at all the basically honest warm tonality of the Koss products.
Koss ESP950 Headphones
The current Koss ESP950 headphones have been in production since 1990, almost 30 years now. By the time they were introduced, I was not listening much to headphones and never really auditioned them. My early headphone adventures are discussed a bit more at the beginning of this earlier thread here in Tom's Corner.
As I now know, my failure to hear the ESP950s for all those years was my loss. After I regained interest in headphone listening a few months back, I concentrated on much more recently introduced dynamic and planar magnetic offerings as documented in the above link and here and here. About the time I purchased a pair of Janszen Valentina Active hybrid electrostatic speakers I also ordered a pair of Janszen's hybrid electrostatic headphones, but despite VERY promising working prototypes being demonstrated at the last couple of AXPONAs, these have yet to see the light of day as a commercial product.
I've listened at AXPONA to some of the newer electrostatic offerings, primarily from HiFi Man and Mr. Speakers. While the HiFi Man versions do sound clear enough to distinguish them from the company's non-electrostatic headphones, they are impact light and treble heavy. The Mr. Speakers Voce are indeed the best in that company's line, but to my ears have not sounded so stunning as to warrant the investment for phones and the separate amp needed to drive them.
Second System
When I first moved to my new home in 2015, I had two dedicated rooms. The realities of married life and new interests cut that back to one converted bedroom for the last couple of years. That's fine, and I'd been able to combine my speaker and headphone listening in that one room with the help of extraordinarily fine headphone amps, most recently the Benchmark HPA4.
But last Christmas I treated myself to a new Dell XPS 7760 27" Touch 4K Ultra desktop all-in-one computer for my home office. The configuration I purchased is described here. The new computer has both extraordinary video quality as well as the best audio of any all-in-one. I thus found myself spending an increasing amount of time watching movies and other video programs at my office desk on the "big" screen—big because at my usual desktop viewing distance that 27" screen has a subtended angle similar to the biggest screen cinema from the front part of the theater.
Yes, the audio speakers that come with that Dell are quite fine—for computer audio. They are not like a high-end audio system, however. But plug in my $200 NAD Viso HP-50 headphones into the stereo mini jack and we are really talking some very fine sound as long as all the special processing available from the soundcard is bypassed. For awhile, I was content. As I've mentioned repeatedly in my prior headphone ramblings, I have great admiration for the sound quality of those NAD phones and their high sensitivity and warm balance make them a perfect match for the relatively low power available from a desktop computer's audio amp.
Then I saw an eBay auction for a brand new Koss ESP950 electrostatic headphone system. I figured the winning bid wouldn't be much higher than the current $500 price for the MassDrop version ESP95X, quite a discount from the usual $1,000 retail of the Koss version, not to mention the $2,000 retail price when the ESP950 debuted almost 30 years ago. My survey of some online reviews indicated that the ESP950 has garnered quite a bit of respect from both owners and professional reviewers over the years with most finding the quality of voice reproduction, the midrange in general, and the overall tonal balance to be strong points of its natural-sounding reproduction. I took a "small" (in terms of my overall headphone investment at this point) gamble and made a bid that I believed could not fail. I did in fact end up winning the auction for just over $600.
First Listen
From first listen the Koss ESP950 everything I hoped it might be, and then some. I knew from the first few moments of listening that these were very special headphones indeed! The overall tonal balance was stunning, as was the level of audible detail and clarity without added brightness. The phones are extremely light in weight, lighter even than the Mr. Speakers Ether 2 which I recently raved about. Not only that, but head clamping is almost non-existent, making the Ether 2s feel, by comparison, like having a vise on my head.
I cannot stress enough the basic difference in sonic quality between these electrostatic headphones and the best of the dynamics and planar magnetics I have for comparison. There is so much more audible detail and nuance, both tonally and dynamically, from lowest bass to highest treble. Okay, I still feel that the lowly NAD Viso HP-50 is the closest to perfection in terms of overall tonal balance. But the NAD bass sounds a bit thick and heavy by comparison, whereas the Koss sounded a bit too thin in the bass for overall neutrality, but for the first time I could hear where the NAD might be erring a bit in terms of balance.
But aside from the overall balance issue, the Koss ESP950 is just so much clearer and obviously lower in distortion than the NAD or any other dynamic or planar magnetic phone I've experienced. And even in the bit-thinner-than-natural bass, there is enough to make me doubt the thinness at many junctures—and there is just so much detail without any over-brightness. Okay, like electrostatic speakers, there is a lack of bass punch and drive compared to dynamic and planar magnetic drivers, but even in the bass the increased clarity and nuance makes up for that on most material.
Keep in mind that for these initial impressions I was comparing the sound of the NAD Viso HP-50s with its stock headphone cable fed from the audio-out mini-stereo jack of my Dell computer compared to the ESP950 fed from the same audio out mini-stereo jack of my Dell computer via the stock stereo miniplug to dual RCA plug cord which came with the Koss phones, to the stock Koss E90 amp/energizer, with the ESP950 played from the Koss E90.
[Continued below]
My recent electrostatic headphone purchases are not my first foray into electrostatic headphones, not by a long shot. I was an early adopter of the Koss ESP/6 electrostatic headphones many decades ago, back in 1968. Yes, they were heavy and uncomfortable, with considerable clamping force. And they had their problems due to their "self-energizing" feature which used the audio signal to polarize the electrostatic elements. This caused the sensitivity of the phones to vary considerably with classical music which had long periods of quiet playing. This was something the factory seemed unable to correct despite my sending them back a few times. But when they were "on," they undoubtedly sounded better in important ways, such as clarity and audible detail without added brightness, than any other headphones I'd ever experienced.
The 1971 ESP/9 was better-yet sounding and did not suffer from the varying sensitivity problem. Removing the self-energizing feature from the headphones themselves to a black box helped the weight and reduced or eliminated the varying sensitivity problem. They were still heavy, however, and the clamping force was just as considerable.
When the various Stax electrostatic earspeakers became available a few decades ago, I listened periodically at audio dealers. The Stax were and are very light by comparison, had low clamping pressure, much larger earcups, and were, of course, open-backed, unlike the early Koss products. Yes, they were yet clearer sounding than those Koss models, but at least part of this was due to the fact that they always seemed bass light and treble strident to me, not at all the basically honest warm tonality of the Koss products.
Koss ESP950 Headphones
The current Koss ESP950 headphones have been in production since 1990, almost 30 years now. By the time they were introduced, I was not listening much to headphones and never really auditioned them. My early headphone adventures are discussed a bit more at the beginning of this earlier thread here in Tom's Corner.
As I now know, my failure to hear the ESP950s for all those years was my loss. After I regained interest in headphone listening a few months back, I concentrated on much more recently introduced dynamic and planar magnetic offerings as documented in the above link and here and here. About the time I purchased a pair of Janszen Valentina Active hybrid electrostatic speakers I also ordered a pair of Janszen's hybrid electrostatic headphones, but despite VERY promising working prototypes being demonstrated at the last couple of AXPONAs, these have yet to see the light of day as a commercial product.
I've listened at AXPONA to some of the newer electrostatic offerings, primarily from HiFi Man and Mr. Speakers. While the HiFi Man versions do sound clear enough to distinguish them from the company's non-electrostatic headphones, they are impact light and treble heavy. The Mr. Speakers Voce are indeed the best in that company's line, but to my ears have not sounded so stunning as to warrant the investment for phones and the separate amp needed to drive them.
Second System
When I first moved to my new home in 2015, I had two dedicated rooms. The realities of married life and new interests cut that back to one converted bedroom for the last couple of years. That's fine, and I'd been able to combine my speaker and headphone listening in that one room with the help of extraordinarily fine headphone amps, most recently the Benchmark HPA4.
But last Christmas I treated myself to a new Dell XPS 7760 27" Touch 4K Ultra desktop all-in-one computer for my home office. The configuration I purchased is described here. The new computer has both extraordinary video quality as well as the best audio of any all-in-one. I thus found myself spending an increasing amount of time watching movies and other video programs at my office desk on the "big" screen—big because at my usual desktop viewing distance that 27" screen has a subtended angle similar to the biggest screen cinema from the front part of the theater.
Yes, the audio speakers that come with that Dell are quite fine—for computer audio. They are not like a high-end audio system, however. But plug in my $200 NAD Viso HP-50 headphones into the stereo mini jack and we are really talking some very fine sound as long as all the special processing available from the soundcard is bypassed. For awhile, I was content. As I've mentioned repeatedly in my prior headphone ramblings, I have great admiration for the sound quality of those NAD phones and their high sensitivity and warm balance make them a perfect match for the relatively low power available from a desktop computer's audio amp.
Then I saw an eBay auction for a brand new Koss ESP950 electrostatic headphone system. I figured the winning bid wouldn't be much higher than the current $500 price for the MassDrop version ESP95X, quite a discount from the usual $1,000 retail of the Koss version, not to mention the $2,000 retail price when the ESP950 debuted almost 30 years ago. My survey of some online reviews indicated that the ESP950 has garnered quite a bit of respect from both owners and professional reviewers over the years with most finding the quality of voice reproduction, the midrange in general, and the overall tonal balance to be strong points of its natural-sounding reproduction. I took a "small" (in terms of my overall headphone investment at this point) gamble and made a bid that I believed could not fail. I did in fact end up winning the auction for just over $600.
First Listen
From first listen the Koss ESP950 everything I hoped it might be, and then some. I knew from the first few moments of listening that these were very special headphones indeed! The overall tonal balance was stunning, as was the level of audible detail and clarity without added brightness. The phones are extremely light in weight, lighter even than the Mr. Speakers Ether 2 which I recently raved about. Not only that, but head clamping is almost non-existent, making the Ether 2s feel, by comparison, like having a vise on my head.
I cannot stress enough the basic difference in sonic quality between these electrostatic headphones and the best of the dynamics and planar magnetics I have for comparison. There is so much more audible detail and nuance, both tonally and dynamically, from lowest bass to highest treble. Okay, I still feel that the lowly NAD Viso HP-50 is the closest to perfection in terms of overall tonal balance. But the NAD bass sounds a bit thick and heavy by comparison, whereas the Koss sounded a bit too thin in the bass for overall neutrality, but for the first time I could hear where the NAD might be erring a bit in terms of balance.
But aside from the overall balance issue, the Koss ESP950 is just so much clearer and obviously lower in distortion than the NAD or any other dynamic or planar magnetic phone I've experienced. And even in the bit-thinner-than-natural bass, there is enough to make me doubt the thinness at many junctures—and there is just so much detail without any over-brightness. Okay, like electrostatic speakers, there is a lack of bass punch and drive compared to dynamic and planar magnetic drivers, but even in the bass the increased clarity and nuance makes up for that on most material.
Keep in mind that for these initial impressions I was comparing the sound of the NAD Viso HP-50s with its stock headphone cable fed from the audio-out mini-stereo jack of my Dell computer compared to the ESP950 fed from the same audio out mini-stereo jack of my Dell computer via the stock stereo miniplug to dual RCA plug cord which came with the Koss phones, to the stock Koss E90 amp/energizer, with the ESP950 played from the Koss E90.
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