Koss ESP-950 review
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kartik

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The Koss ESP-950

Firstly, it’s great to be back after a self imposed sabbatical from Headfi.
When I was last here, I was starting to tire of my Grado SR-325s after listening to Jimmy’s RS-1s and Lan’s K1000s. Just as I was getting ready to jump ship, a drastic career change sent me careening into a 90 hour work schedule at the hospital. Now, as my year is winding down, I was starting to suffer the pangs of longing to get back into headphones. I was really interested in trying out electrostatics but wasn’t sure what I wanted. I thought long and hard about the Stax SR-005 Mk2 and the 4040 signatures as well as possibly even a used Omega. I had heard the HE-60s at the NYC meet (out of a KGSS) but wasn’t terribly impressed and these are hard to find. I then found the Koss ESP-9 on ebay as an option, but had significant trepidations about going vintage. Looking up reviews on the Koss electrostatics on Headwize and Headfi, I found that there were some really nice things about the newer Koss ESP-950s.

Some of the good points on the reviews included:
1.Good midrange, with a richer, more lush presentation than the Stax
2.Fairly detailed
3.Comfortable (This is a major grouse my head had with the Grados)
4.Price: $599 on Amazon including energizer/amp
5.Unconditional lifetime warranty

Some of the known issues with these cans included
1.Squealing issues (never figured that out, but it was a major grouse for most owners)
2.Poor performance of the provided amplifier
3.Non-compatibility with other electrostatic amps (needs a custom adaptor)
4.Build quality
5.Lack of reviews
6.Sound quality, some reviewers like edelstrow and Darth Nut really like it, others including Kevin Gilmore , Calanctus and Jpelg were kind of lukewarm about their performance.

Koss ESP/950 E90 Specifications

SPECIFICATIONS
ESP/950

Physical Specifications
Size of earcup: Approximately 150 mm h x 100 mm w x 40 mm d (including cushions)
Cushions: Large foam filled leatherette type for high ambient noise isolation and conformance to facial structure.
Headband: Extendable, stainless steel band with self adjusting, pivoting yokes and headband release mechanism.
Headband Cover: Wide leatherette style vinyl with 12 mm thick polythylene foam padding.
Yokes: Horizontal and vertical pivoting with integral headband lock and detach mechanism for convenient storage
Weight: 12.45 oz. (353 gm)
Cord Length: 47 inches (182.9 cm)
Extension cord length: 72 inches (182.9 cm)

Electroacoustical Specifications
Frequency response: 8 Hz to 35,000 Hz
Sensitivity: 104 dB, 100 Vrms differential input a 1 kHz
Diaphragm radiating surface area: 7 sq. in. (45.6 sq. cm)
Diaphragm: Ultra-low mass 1.5 micron C grade polyester film electronbeam coated with a proprietary semiconductive material 250 A thick.
Acoustic Design principal: Circumaural open air design incorporating minimal acoustic damping.

E/90 Energizer/Amplifier

Physical Specifications
Dimension: 65mm h x 110 mm w x 155 mm d
Weight: 17 oz. (482 gm)

Electrical Specifications
Frequency response: 1.6 Hz to 50,000Hz (-3dB points) 100 vrms differential output
Distortion (THD+NOISE): 0.001% at 1kHz and 100Vrms differential output
Input Impedence: 100k ohms
Input level: 1 Vrms (for full power output)
Voltage Amplification: 60 dB
Audio output voltage: 600 Vrms differential, 2300 Vrms push-pull with soft limiting
Channel Separation: - 80 dB at 1 kHz, 100 Vrms differential output
Signal to Noise: -100 dB at100 Vrms output
Bias voltage supply: 600VDC
Signal Polarity: Absolute Phase (non-inverting)
Volume control: Dual concentric continuous audio taper high quality potentionmeter with split shaft for balance
Indicator: Combination Power ON and battery condition dual-color LED
Switches: Power ON/OFF rocker switch
Input jacks: (a) RCA type (L & R); (b) 3.5 mm stereo; (c) AC/DC adapter/Battery pack
Power consumption: 320 mA DC current at normal listening levels.


Most people recommend listening to headphones before buying them and while I completely subscribe to this theory, the two headphones I had narrowed down to were nigh impossible to find at a Best Buy; i.e. Stax SR-005 and Koss ESP. When my wife picked up a new job, and offered to buy me a gift, I decided to bite the bullet and go for the Koss ESP purely for the comfort factor, because all my experiences with plugs have not been pleasant.

Out of the carton, first appearances were favorable because Koss includes a really nice carrying case for the headphones, amplifier, battery adaptor and cables. Koss does include some 1/8 to 1/8, 1/8 to RCA and RCA cables with the cans. Not that I’m using any of these, nor planning to.

Unfortunately, the favorable impression the outer case gives way rapidly to the icky feeling on holding the plasticky and ugly looking headphones, that made the build quality on the Grados look stellar. The amplifier was equally unimpressive with a really cheap looking volume knob and cheap looking RCA plugs.
That said, the minute I put them on after a 20 minute warm up, the impressions improved even before the music. For starters, these are much more comfortable than the grados thanks to their around the ear design. Another plus is the isolation. Although not closed cans, there was definitely better isolation from outside sounds.

Even on initial pre-burn in listening, these headphones sounded much easier to listen to than the SR-325s with a far-less fatiguing sound. That said, this was not because of a lack of detail. Now after burn in the Koss is far more detailed than the Grados on their best day. OTOH, the bass is very different from the Grado. On initial listening the bass sounded thin. With burn-in the bass certainly is filling in but sounds very different from the grados. It seems to me that the bass is lower and better defined, but the Grados certainly sound louder. Speaking of louder, the Koss can really get astoundingly loud without much distortion.

After burn-in, the Koss is a very different animal. It certainly needs at least 2-3 hundred hours to reach its final colors. While certainly very pleasant to listen to, their sound is not really that transparent, rather an interesting color. It really shines on some tracks while mediocre on others. It does a wonderful job with the piano and the bass which really come out on their own as string instruments, while its performance with wind instruments and badly recorded vocals is mediocre. While I rate its performance with vocal music above average, choral music is nothing short of stunning with brilliant separation of individual voices. The electrostatics intrinsic ability to resolve sounds really well really shines through while still being a nice rich sound, somewhere between electrostatics and dynamics.

Another issue that seems to have had a limited improvement since burn-in is the soundstage. While initially these sounded completely in your head, the soundstage is definitely more spacious now. Except of course for the noticeable large hole in the front of your face. The hole is a little less well defined with LPs and SACD but the compressed sounds of CD have a strange soundstage.

A major issue with the headphones in prior discussions has been the bass response on these cans. The main thing I’ve noticed is the absence of significant harmonics on any of the frequencies. In the mids and highs this seems to translate into non abrasive sound (A welcome change from the Gratos, I used to listen to!) but with regards to the low end this translates into less aggressive sounding bass. With burn-in and time the bass seems to bloom a little more but this is no bass-head. As I’ve been listening to these, I find that I’ve started liking the bass response on them more and more with time. It just sounds more real. A bass sounds like a bass and a drum sounds like a drum. The lack of harmonic confusion also leads to a much faster and cleaner attack, longer decay and correct timbre and tonality of most instruments.

Overall, I really enjoy having these cans. I think for the price ($599 Amp + headphones) it is a really good buy for starter audiophiles and definitely superior in a head to head with the old SR-325s. Are they superior to other electrostatics? I really don’t know. I think based on non-A/B comparison, they sound richer than most electrostats with a more dynamic kind of sound. An amp upgrade to a KGSS/BH may be something for the wealthy to consider, but at that point it may be reasonable to think of getting the O2s. The build quality is unispiring but the overall performance compensates considerably. A pair of can for the ears not the eyes.



Associated Equipment

Sharp SM-SX1 amplifier
Sharp DX-SX1 SACD player
Grado PH-1 phono pre-amp
VPI Scout with JMW-9 and Grado Platinum
Signal Cable analog V2 (Sharp headamp)
Headphile Silvers (CDP Amp)
Headphile BlackGold (VPI  Grado PH-1)
Headphile BlackSilver (Grado  Sharp)
BPT-1 Power regenerator



Music Used

LPs
Nirvana: Nevermind
REM: Out of time
Linkin Park: Meteora
Moby: Play
John Lennon: Imagine
Tchaikowsky (Antal Dorati) Nutcracker

SACDs
Got Swing (Erich Kunzel and Cinncinnati Pops)
Telarc SACD Sampler I
Alison Krauss + Union Station LIVE
Deep Purple Live
Peter White: glow

CDs
INXS : The greatest hits
Santana: Shaman
Rush: The spirit of Radio
Motion Picture soundtrack: Swades
The Corrs (Live at Dublin)
 
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EdipisReks

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interesting review on phones that don't get mentioned much! i agree that the system is definitely priced right for electrostatics.
 
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catscratch

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The amp is battery-powered, right? How portable is it? How much sound do they leak and let in? How big are they, next to other full-size cans? And can you post pictures? Yeah, lots of questions, this.

I saw a pair of these on Ebay for $100-ish (!), but didn't go for it. I'm kicking myself now. These could be pretty cool for full-size transportable use. I'm getting tired of using canalphones at work and missing calls, or having to take them out again and again to talk to people. The SR-001 is nice at work, but something comfier wouldn't be taken amiss. And, I've got an SRM-313 to use at home if the Koss amp sucks.
 
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kartik

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Quote:

Originally Posted by catscratch
The amp is battery-powered, right? How portable is it? How much sound do they leak and let in? How big are they, next to other full-size cans? And can you post pictures? Yeah, lots of questions, this.

I saw a pair of these on Ebay for $100-ish (!), but didn't go for it. I'm kicking myself now. These could be pretty cool for full-size transportable use. I'm getting tired of using canalphones at work and missing calls, or having to take them out again and again to talk to people. The SR-001 is nice at work, but something comfier wouldn't be taken amiss. And, I've got an SRM-313 to use at home if the Koss amp sucks.



1. No. It has both a wall wart and a battery adaptor
2. As portable as a headroom home
3. Leak tons of sound. Don't let much in.
3. These are the biggest electrostatic diaphragms in the world. But because of plastic construction they are light and extremely comfortable for extended use. Not so great for hot days but few headphones really are.
4. 100 ish is a great deal (the actual retail from Koss Inc. is currently $1000, Amazon is $599)
5. They are technically transportable in the provided bag with a PCDP/Ipod and battery unit, but it is not really competing with Etys for portability.
5. Would probably sound great with the SRM-313 but you will need an adaptor.
 
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Welcome back, Kartik. I was worried about you after you seemingly dropped off the face of the earth! Glad to hear that both you and your wife are doing well.

I had the ESP950's for a short time (from Amazon too), but ended up sending them back after a month. Sound was pretty good, but not...I don't know,...exactly "right". Dunno why, and it has been a while since hearing them. I recall them being pretty light in the bass area. But as you say, a good value compared to other mid-priced setups, since it includes a matching amplifier (as it is) too.

I often wonder what they would sound like out of a KGSS electrostatic amp. Maybe you can use the Koss extension cable to fashion an adapter to a Stax connector?

Btw, you comin' to the next meet?
 
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kartik

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Not sure if I can come to the next meet. My schedule hasn't got much better, I've just adapted to it a little better.

Back on topic.

The koss do sound strange on some recordings (particularly while burning in) but they do get better with age. I was thinking of getting a Macalister Audio ES amp (cheaper than KGSS) but money is again an issue for now. The amp manufacturer had offered to fashion me an adaptor if I had gone through with the deal. The alternative would be to have Larry (Headphile) build it since he is so good at fabricating cables and adaptors.
Since you brought the issue of the meet, I don't mind sending in the koss, even if I can't make it.
 
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I'm interested in getting a pair. Would you mind posting some pics? I'm also concerned about the amount of plastic. The more pics, the better.

Thanks.
 
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kartik

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Another thing I noticed. These headphones are not well suited to low level listening and sound fairly muddy at low levels. When the volume is cranked up both the bass and the details improve in a startling manner. No distortion, even at insane levels. I might seriously consider a KGSS as my next purchase. Particularly since KG thinks that the amp is the weakest link.
 
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Quote:

Originally Posted by kartik
Trying to post pictures, unsuccessfully. Here is the link to the Yahoo folder


I had a heckuva time trying to keep links to the Yahoo photo albums intact-- Yahoo keeps changing the URLs for the individual images! I finally gave up and signed on with PhotoBucket, which works well.

I've noticed that those in the know post pictures that have URLs that look like photos.head-fi.org.xxxx. Can anyone tell us if there really is an on-site photo posting function?
 
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kartik

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Quote:

Originally Posted by wualta
I had a heckuva time trying to keep links to the Yahoo photo albums intact-- Yahoo keeps changing the URLs for the individual images! I finally gave up and signed on with PhotoBucket, which works well.

I've noticed that those in the know post pictures that have URLs that look like photos.head-fi.org.xxxx. Can anyone tell us if there really is an on-site photo posting function?



Is there a problem with the link I posted? I thought it seemed to work OK to the photo album. I'd be glad to email the pics to anyone who could post them differently (more accessible!).
 
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This was my first ever set of high end headphones(esp-950). I was new to the whole high quality headphone bit and didn't like the fast leanish bass compared to the sealed sony cans i had so i returned them and bought a headroom amp with a senn 580. I bought it at the time cause it got a positive review from stereophile (this was all more than 10 yrs ago btw). again i was dissapointed! man, I liked the koss better. Then i got my grado sr-80s. something i finally loved.
Today I wonder how I would love these headphones cause since then I loved my 580s more and more and sort of changed my sonic tastes a bit. I do regret returning them to j&r. I got them for 499 back then.
 
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Quote:

Originally Posted by kartik
Is there a problem with the link I posted?


No, the link(s) work fine. I thought you were trying to post photos.


Quote:

Originally Posted by donunus
...I returned them and bought a Headroom amp with a Senn 580. Again I was disappointed! Man, I liked the Koss better...


There are endless debates about the thinness of "electrostatic bass", but once you've heard them, it's hard to give up electrostatic mids and highs. But you're right, your ears accommodate themselves to whatever headphone you're listening to, just as your eyes automatically white-balance what they see.
 
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Quote:

Originally Posted by wualta
No, the link(s) work fine. I thought you were trying to post photos.



There are endless debates about the thinness of "electrostatic bass", but once you've heard them, it's hard to give up electrostatic mids and highs. But you're right, your ears accommodate themselves to whatever headphone you're listening to, just as your eyes automatically white-balance what they see.



The thing about being white balanced to detailed headphones like stats... everything will sound slower less defined and murky and you will still keep wanting more cause there is always something missing. The Head-Fi Sickness. The grados made me happy because it made me listen to the music more than the details. The grados sort of fixed upgradeitis for a while. The evil audiophile still prevailed and upradeitis is back
dammit
 
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