[milosz]

There's some discussion of these electrostatic 'phones in various threads, and reviews, but I thought it would be worthwhile to dedicate a thread to the ESP-950.
 
 
The ESP-950 doesn't get the respect it deserves, in my opinion.  It doesn't have the brand cachet of Stax -  Koss ESP-950's are the only current electrostatic headphones from Koss, whereas Stax makes ONLY electrostatic headphones and their driving devices. (Electret headphones are also a kind of electrostatic headphone.)  So, since Koss isn't associated only with high-end products the way Stax is, it can't get no respect....
 
Koss has a long history of electrostatic headphone development, going back to the late 1960's I believe. I bought a pair of Koss ESP-9's in 1970, and drove them with a Harman-Kardon Citation 12 power amp / SAE Mark XXX preamp. Source was an ADC XLM cartridge or a Shure V15 in an AR XA turntable, plus an Akai GX365 open reel deck running at 7.5 ips. With Scotch 207 tape!  Hahahahaha  I even remember doing the bias setup for that tape on that Akai deck.  That was a LONG time ago!
 
But the ESP-9's were arguably the best headphones of the day. Stax had the SR-1 but I never saw them in the US and reports I heard said that the ESP-9 was superior.
 
There were the ESP-6's which are not the greatest- the earcups have have built-in step-up transformers and derive bias from step-up / rectification of the audio. They weigh a ton and don't sound as good as the ESP-9's. The ESP-6's predated the ESP-9's I believe.
 
The ESP-9's were replaced by the ESP-10's, which had a more upscale appearance and were said to be better sounding, and although a friend of mine has owned them for years and swears by them, I have never spent any time listening to them.  
 
All of these earlier Koss electrostatics were closed designs.
 
Here's some info on the Koss electrostatic stuff, including reviews back from  'the day.'  http://wiki.faust3d.com/wiki/index.php?title=Koss_Electrostatic_Line_Overview
 
Now we come to the ESP-950's. They are an open design, and come with an amplifier instead of just a coupling transformer / bias supply which you attach to your speaker amp, as the ESP-10, -9, -7 and -6  did.
 
I haven't compared the ESP-950 to earlier Koss efforts, but I DO have Stax SR-007 MK II's, and a pair of Stax Lambda Pro Signatures.  (I also had a pair of Lambda Pros, but I sold those.)  I would say the the ESP-950 is in the same class as the Stax 'phones, though it does sound different.  My ESP-950's have a Stax cable on them, and I've only listened to them through my Stax SRM-1 MK I and my Stax SRM-T1. Their sound is VERY GOOD, though different from the Stax. 
 
My comparison in a nutshell:

1. ESP-950  has more bass impact than Lambda Pro Signature, a warmer midrange and although the Koss have a lot of inner detail, they do not offer the exquisite level of detail available through the Lambda Pro Signatures.
2. ESP-950 sound as 'clean' as the SR-007's but have a more colored sound, the SR-007's sound closer to natural. That is to say, the ESP-950's distortion is way low and ringing, energy storage, and so on is low, but there is a bit of a midrange emphasis from the Koss while the SR-007's seem more closely balanced to offer a neutral sound.  Keep in mind, of course, that the SR-007's cost roughly three times the ESP-950's street price, and at that price the ESP-950's include a decent amplifier. (The Koss amp is good sounding, not as good sounding as the Stax I mentioned, but still is not bad. And the Koss amp runs off batteries... which can be useful at times.)

 
I would have to say I prefer the Koss to the Lambda's by a slight margin, largely because they offer better bass impact. And while the Koss ESP-950's are more comfortable than the SR-007's, I have to say that I find the sound of the SR-007's to be superior in many ways.
 
If you look at Purrins thread covering CSD plots, you can see that the ESP-950 performs quite well. http://www.head-fi.org/t/566929/headphone-csd-waterfall-plots/30#post_7724844   and Purrin mentions that he likes the way the ESP-950's sound.
 
So, I ask, why don't the ESP-950's get more respect?  Is it because they're from a company who doesn't really have the high-end market in their sights? Are the Koss ESP-950's falling victim to the if-it's-not-$5,000-it-can't-be-any-good snobophiles?
 
I admit, they don't exude build luxury like the top-of-the-line Sennheisers or Staxes, but their sound is somewhere between really very good and excellent, and isn't SOUND what it's all about?

 

[Anaxilus]

Here is the most recent 950 thread and there's one or two others but I like your initial post too.  Maybe it should be called the 'Why not the Koss ESP950 thread?'
 
http://www.head-fi.org/t/553587/something-new-with-the-koss-esp950
 
I would say it s a combination of things.
 
1-Cheap price + cheap build = cheap sound in most people's minds
 
2-Stock energizer does hold it back compared to most Stax amps and the Koss termination is ust another impediment to using alternative amps. 
 
I took my 950's over to Craig Uthus to sample his new Electra stat amp along w/ the SRX, 507, O2, 009.  He had neither heard them or heard of them before.  Last I heard he is buying himself a set.
 
You forgot to mention the Lifetime warranty btw.  

 

[Currawong]

I was looking at these the other day when I was on the Koss web site. For some reason I had the impression that they were not in production. It was a surprise to find they are still being made.

 

[sharkz]

Its good to see a current thread devoted to these. I have been been interested in these as an entry into electrostats for several years but having no way to audition them has been a huge issue for me. It seems like the only reasonable way will be to get to a meet where someone has them. I am curious to see what others say about them though.

 

[FrankCooter]

These do come up every now and then, and people that hear them are generally positively impressed.  I own a pair of ESP-950's as well as two  different Stax lambda models. On a sonic level, I greatly prefer the Koss to the Stax. Unfortunately, the Koss labor under a number of handicaps, the greatest being a driver design defect that presents itself in the form of  an intermittent low level "squeal" that is really only noticeable during periods of silence. Some examples never get the squeal at all. Some have it through multiple sets of drivers. Mine  have had at least three sets of drivers. Right now, the "squeal" is intermittent and very low level, but it's definitely there. The good news is the exceptional warranty policy. There is an absolute "no questions asked" lifetime warranty that goes with the headphones regardless of resale. You don't even need any paper work. All my driver replacements were under warranty with absolutely no hassle.
 
The build quality in general is a bit plasticy and cheesey, but not that different from the lesser Stax, or the  "Europlastic" Sennheisers.
 
The connector issue can easily be solved by cutting off the end of the supplied extension cable ( or buying a second one for about $15.00) and replacing the plug end with a Stax compatible Amphenol plug.
 
A final, and very subjective observation, is that these headphones, unlike Stax, seem to have no advocacy group here. But like Stax, the company makes essentially no effort to reach out to the community.. 
 
I like these headphones, and would really like to see them make an effort at an all out high-end product, but I'm not holding my breath.

 

[seacard]

A $600 electrostat?  That's way too cheap to be considered high end.  In fact, it is only 30.85% as good as an LCD-3.  Now, if Koss raised the price by a couple thousand, I might consider it.  Until then, I'd much rather listen to [note to self: insert name of some mediocre overpriced headphone that people rave over because it is really expensive.]

 

[dagothur]

$600 for the system total, not just the headphones.  Somebody should do a comparison against the LCD-2s to see if a pair of ESP-950s would be a worthy addition.

 

[charliex]

Quote:

$600 for the system total, not just the headphones.  Somebody should do a comparison against the LCD-2s to see if a pair of ESP-950s would be a worthy addition.

Koss list price on their site is $999.99

 

[dagothur]

Quote:

Koss list price on their site is $999.99

 You can find it for $600-$700 most other places.
 
 

 

[Anaxilus]

Quote:

$600 for the system total, not just the headphones.  Somebody should do a comparison against the LCD-2s to see if a pair of ESP-950s would be a worthy addition.

First you'd have to find a good set of LCD2s, either version, and then it's really two different sigs completely.  The LCD2 is going to have that lusher sig and the 950 is quicker yet still warm and balanced w/o being typically dry or analytical like a brighter, more aggressive stat.  This is using the stock energizer.  IMO the 950 can scale better but the price of doing so definitely makes them worthy of this forum.
 

 

[NamelessPFG]

I've been tempted by the ESP/950 before, but had a few concerns.
 
-Some have complaints about the build quality over time, though I'm not sure if it's more about the headphones or the driver unit. Fortunately, Koss has a lifetime warranty. Unfortunately, that lifetime warranty is only available if you buy brand new from a dealer. (I'm guessing this is why Koss isn't really respected in the audiophile community.)
 
-I know now that, comfort-wise, the Stax Lambda design is a safe bet, probably the most comfortable headphone I've ever worn. On the other hand, I've never worn the ESP/950 before and don't know if it can meet that standard of comfort. Needless to say, I value long-term comfort just as much as sound quality. (This goes for a lot of other headphones, actually...but especially vintage Koss ESP/9s, which had these fluid-filled earpads that are no longer available.)

 

[n3rdling]

The ESP950 is seriously awesome, I'll probably end up picking up a set sometime.  Frank, I remember somebody (I think cetoole) opening up the E90 and checking the bias voltage.  I think there was some conflicting info that showed a different bias for different E90s.  Do you think the squeal might be a result of using the wrong value bias?

 

[FrankCooter]

Quote:

First you'd have to find a good set of LCD2s, either version, and then it's really two different sigs completely.  The LCD2 is going to have that lusher sig and the 950 is quicker yet still warm and balanced w/o being typically dry or analytical like a brighter, more aggressive stat.  This is using the stock energizer.  IMO the 950 can scale better but the price of doing so definitely makes them worthy of this forum.
 

I own both, and I'd pretty much agree with the above statement. The LCD2 has a deeper and more articulated bass, and I slightly prefer it's lusher, more visceral midrange, but the Koss has a slight, but noticable, edge in speed and detail. Overall  sonic quality is on par and boils down to personal choice.
 
No comparison in build quality however. The LCD2 is a beautiful piece of high-end art that oozes quality. The Koss is a cheap plastic toy in comparison.
 
I wouldn't pay $1k or even $650.00 for the Koss, but I'd definitely pay $450.00 for a used pair.
 
The supplied amp or "energizer" as they call it, isn't great but it's perfectly listenable. The ESP-950's respond well to amplification upgrades. I'm running mine off a DIY tube amp, and I know of others reporting good results with Kevin Gilmore designs. I spent about $350.00 building my amp, The entry level Gimore designs can be built for around the same price.
 
 

 

[milosz]

Quote:

A $600 electrostat?  That's way too cheap to be considered high end.  In fact, it is only 30.85% as good as an LCD-3.  Now, if Koss raised the price by a couple thousand, I might consider it.  Until then, I'd much rather listen to [note to self: insert name of some mediocre overpriced headphone that people rave over because it is really expensive.]

I think a 35 mm machined billet front panel on the energizer/amp would improve them also....   They should also claim that all the unobtainium used is six nines pure (99.9999 %)*
 
 
*As far as I know, doing a QC assay on "six nines" copper is beyond the abilities of all but a few highly-specialized research labs in the world.  I defy ANY audio cable manufacturer to show me that they are doing NIST-traceable purity assays to prove that all incoming lots of copper wire they use in their cables is truly "six nines OFC."  Also, although some cable manufacturers specify they use "six nines silver" - I do not believe that silver of this purity level is available at all on the market, at any price. It would have to be special made - IF it is even possible- and I don't think that there is even one high-end cable manufacturer out there who is refining his own metal and drawing his own wire.   In my opinion the only thing that is "six nines" purity in these products is the ultra-pure B.S. used in their marketing.

 

[milosz]

Quote:

These do come up every now and then, and people that hear them are generally positively impressed.  I own a pair of ESP-950's as well as two  different Stax lambda models. On a sonic level, I greatly prefer the Koss to the Stax. Unfortunately, the Koss labor under a number of handicaps, the greatest being a driver design defect that presents itself in the form of  an intermittent low level "squeal" that is really only noticeable during periods of silence. Some examples never get the squeal at all. Some have it through multiple sets of drivers. Mine  have had at least three sets of drivers. Right now, the "squeal" is intermittent and very low level, but it's definitely there. The good news is the exceptional warranty policy. There is an absolute "no questions asked" lifetime warranty that goes with the headphones regardless of resale. You don't even need any paper work. All my driver replacements were under warranty with absolutely no hassle.
 
The build quality in general is a bit plasticy and cheesey, but not that different from the lesser Stax, or the  "Europlastic" Sennheisers.
 
The connector issue can easily be solved by cutting off the end of the supplied extension cable ( or buying a second one for about $15.00) and replacing the plug end with a Stax compatible Amphenol plug.
 
A final, and very subjective observation, is that these headphones, unlike Stax, seem to have no advocacy group here. But like Stax, the company makes essentially no effort to reach out to the community.. 
 
I like these headphones, and would really like to see them make an effort at an all out high-end product, but I'm not holding my breath.

I have heard about this "squeal."  My ESP 950's don't do that. I think that some do, and some don't.  My original pair of ESP-9's used to have a little of this (in 1970...)  It sounded like arcing or static discharge of some sort, very very quiet but still audible.  If I jiggled the plug it would stop, and usually not come back for a long time.
 
Yeah they are "plasticky" in terms of construction but the fit and finish is good -   for plastic. But, being plastic, they are also very lightweight and quite comfy.  And even though they are plastic, they seem quite sturdy.
 
The earpads are leather.  Which you don't get on most Stax....
 
Hey!  Maybe that's it!  The earpads might be made of pigskin leather, hence the squealing....