KOSS ESP6 REFURBISHED VINTAGE ELECTROSTATICS
Sep 19, 2009 at 8:54 PM Post #61 of 94

ourfpshero

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here is a cheap adapter for these cans and others like it (electrostats, piezos such as a pioneer se-700 or 500)
a radio shack 1/4 inch headphone mountable jack. cost 4$ for a pack of 2. put a little wire on for left, right, and ground (only one ground needed), plug into receiver, and good to go


using this livened up the esp6 a lot. some real bass coming through now! (though not a lot). using this on my pioneer se-500 piezos works ok, but i feel those still need more
 
Sep 22, 2009 at 12:07 AM Post #62 of 94

ourfpshero

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hers a few comfort mods i did. larger headband from a realistic pro ii (koss pro4aaa oem) and some mega thick earpads. the plastic headband needs more cushion (it has almost none) but now it fits me well
 
Jul 24, 2012 at 11:21 PM Post #63 of 94

auraladdiction

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Do these headphones need a power supply besides a direct connection into a receiver?  I have a chance to get these headphones for around $40 with all the components including the case.  I have an old Sansui G-7500 stereo receiver which I plan on hooking the headphones into.  The receiver has an 8 ohm impedance which should correspond with the headphones.  Or could I just plug the headphones straight into the receivers headphone jack?  Since there is a diagram at the bottom of this ad ( http://wiki.faust3d.com/wiki/images/a/a6/Esp62.jpg ) that shows the headphones being plugged straight into a receiver.  I am new to electrostatic headphones and this forum so any information would be greatly appreciated.  Thank you!  
 
Aug 11, 2012 at 5:25 PM Post #64 of 94

karlsonklam

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they're self-energizing from the audio signal.   I picked up a pair but could not get sufficient power from a TPA6120A2 amp to get them going.  I'd like to know from owners what amplifier power range is good for ESP6 to achieve full dynamics  - a few of my power amps are low power single ended tube - one around 7 watts maximum - is that enough voltage?
--also, do the stock value capacitors hold charge long enough to deal with some genre where there are relatively long periods of either silence or soft sounds?
 
Apr 24, 2015 at 6:09 PM Post #67 of 94

Tinkerer

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I know this is an old thread but I thought I'd chime in that it's still helping people to restore and modify these things today. And they're still playing better than many lower end modern midrange headphones. Not bad for something from the 60's.

aIkZJXX.jpg
 
Apr 25, 2015 at 11:26 PM Post #68 of 94

Tinkerer

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Forgot to mention, Brainwavz HM5 pads fit these just like they fit the old Koss Pro 4A's. And the padded headband came from a similar vintgage era Realtek clone of the Koss 6A

Also modded to removable 3.5mm cable and a few other things. There's 4 conductors in the main cable that allows you to rewire it to standard balanced too even with all the circuitry in the cups.
 
Jul 7, 2015 at 6:51 AM Post #69 of 94

Oljazzer1

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Greetings to all. Firstly, I would like to thank Edstrelow for his original article, which is very informative and very clearly written. I have a pair of ESP6's which I bought here in England in the late sixties (yes, I am a Dinosaur !), and which I used extensively until 1975 when my situation changed and I placed them into storage. Fortunately I found and read Edstrelow's piece before even trying them, since when I opened them up I found (exactly as with his pair), the liquid in the earpads had all but disappeared, and the foam damping inside the cups had become an unrecognisable gooey mess that had contaminated all the electronics. I will be refurbrishing them shortly, but I want to replace the pads completely. I can't find any mention of spares on the Koss website (quote) "I was able to purchase e new set of conventional, i.e. no liquid filled earpads, from Koss for $5.00" , would anyone know of Koss's part number for these? Also, is there any particular foam recommended to use as replacement?
 
With regard to the level of sound changing with signal, I can tell you that this was always apparent even from new when listening to the quiet sections of music with a wide dynamic range, but it may be that modern diodes with a lower leakage can be sourced - I will endeavour to find out. The original sound quality was superb, and comparable to my speakers at the time, the original Quad Electrostatics (which I still have, but whose size requires me to use LS35a's in my small listening room). I had never found the weight of the ESP6's to be a problem although this may be due to the fact that we Dinosaurs have extremely powerful neck muscles !
 
Aug 3, 2016 at 7:05 AM Post #70 of 94

SupaRai

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Hello, i grabbed this thread out of Nirvana, hope this is ok. I am from germany, so english is not my origin language and perhaps i get in trouble with some specific words... Sorry for this.
 
The reason, why i grabbed this thread is because someone gifted me a Koss Esp. 6. Now i am looking for a way to open them. Please, can you give me a guide how to do this?
 
Actually I have no transfer switch. Is it possible to use another device? Or to built these switch by myself... I am a novice in electricial things, but i will have professional help by my side. Can someone help me with an electronic schematic? Or is the schematic picture in the starting thread enough?
 
So, if i get these headphones "running", i would like to change the ear cushion. Do you have an advice, which product fits?
 
For now i thank you for reading und i would be pleased for a reply.
 
Well, by then,
Raimund
 
Apr 5, 2017 at 6:23 AM Post #71 of 94

WallofHooligans

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Anyone have a set of these that they wouldn't mind letting go? PM me if you feel like it.
*Update*
Finally snagged a pair. I'm in the process of restoring them. As stated many times in this thread, the dampening is fully rotted, but it looks like I was lucky enough to get dry rot and less gooey decayed foam. Pictures to come.
 
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May 8, 2017 at 7:08 PM Post #72 of 94

WallofHooligans

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So here's the skinny. The Koss ESP6 is a bitch to open up and fiddle with because of the way that the bits are sandwiched. I like the design, but there's parts that could have been improved on. If you're having trouble figuring out how to open your cans, please make note of how many visible screws you can see. The inner four are for removing the driver, the outer four are for removing the housing. You MUST open the housing to remove the driver. If you only see four, remove the black tape adorning the inner edge of the baffle.

To start, I tested whether or not my pair had live drivers by plugging it in and playing it. At max volume from my Micca Origen+, it was whisper quiet. Still, both sides worked at the same volume. I opened them up to reveal the transformers wrapped in yellow tape, and noticed a layer of foam...
IMG_3402.JPG
(Left Earphone)
The foam here on both sides crumbled into dust at the lightest touch. I suggest removing it slowly and carefully, in the biggest chunks you can. The foam here doesn't add much to the acoustics, so don't worry too much about replacing it. Check your boards for blown parts.
IMG_3414.JPG
(right side)

My boards were fine, but the foam blocks underneath the PCB board were the scary bit. They smelled mildly acidic and like mildew. There's four threaded nuts to unscrew before continuing. Bit size was 4.5mm.
Inside there's a surprise!
IMG_3407.JPG
IMG_3406.JPGYum Yum! It crumbles like dry cake and is stuck to the board. Take note of the size and shape of this foam. You will need to replace it.
I spent quite a lot of time pulling what I could off the board. A useful technique here is to pull up what you can in a few tries, and then go over what you've done with a soft toothbrush.
IMG_3408.JPG
This is what we're left with. The driver side has those two squares of rotten felt material over the inner stator plate. Mine looked pretty okay after removing it, but you may end up in worse shape. Make note of the felt, you will have to replace it.
IMG_3410.JPG
---
IMG_3416.JPG
If you find that your cans are making a buzzing distortion sound, you may need to open the drivers up to remove the dust and hair, god forbid any has entered. I was able to clean mine VERY GENTLY with the end of a clean, unused paintbrush. Pick a brush with very soft bristles. No pig hair bristles, Bob Ross.---


IMG_3409.JPG

The tasty cake foam is gone, but it has heavily corroded the traces on my pcb. Some portion of the foam sticks to the transformer, burnt into it and stuck with surprising tenacity. I used a hard steel awl and many applications of deoxit D100 to do the work. This isn't a singular night process, so be forewarned.
Three days later and I've come up with this.
IMG_3418.JPG
IMG_3419.JPG
I tried a lot of different cleaners here so you don't have to. Stick with the deoxit. White vinegar did okay at softening the green junk on the boards, but I wouldn't recommend it for any length of time. Other stuff used, brasso cleaner, ethyl alcohol wipes and rubbing alcohol. All of them work with some varying success, but again I doubt anything cept for deoxit will leave your headphones perfectly unscathed. Go to the dollar store and buy some disposable materials.
That's all she wrote. I replaced the materials I had disposed of and slapped them back together. There's still some problems, namely my right driver makes a farty sound below 24HZ and both cans have a little bit of distortion above 17KHZ. I actually bet I could fix the second problem with new capacitors perhaps. I'm not sure the low flapping sound can be fixed, maybe by heating the film to remove sloppiness.

You'll probably need to replace the black tape on the baffles after you get these things back together. DO NOT LEAVE THE FOUR INNER SCREWS EXPOSED. YOU WILL GET SHOCKED. I DID IT ON A LOW POWER SOURCE FOR SCIENCE. This is the part of the design I'm not fond of. Oh well.
 
Apr 17, 2020 at 9:49 AM Post #73 of 94

c3kkos

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Hello everyone!

I've got an old pair of KOSS "ESP 6 A", and long time ago i made a promise to myself, i gotta repair these!

The sound quality was poor, the bias going on and off so fast..

I decided to open up the cups and of course i found the foam sea that melt upon everything.

It took me a while to clean up, 3/4 times as the users here already suggested. CORROSION, MY GOD CORROSION EVERYWERE!! hehe

After cleaning/deox i decided to replace all the 0.0068 ceramic disc capacitors, since i was still unsatisfied with the sound. too much distorsion, and too much roll off on basses and highs.

Bad luck, it didn't helped a lot. I think the major improvements went from resoldering all the old traces, with new, fresh solder material. The bias is much more stable, clarity of sound came back

BUT..... i still have NO bass extension... and a very BAD distortion in both channels when i feed more power into the cups. I'm using the output of one old Pioneer 30w + 30w directly. It feeds enough power but ESP 6-A is not working well with all those Watts.




I have no idea how they sounded when they were brand new, since i found these pair in a flea market, bought for 10€ (listed as not functioning)

Well, hope to find some answers, now its time for pictures of my work:


8qnjhBE.jpg


RgJU4iA.jpg
Z9JGBOY.jpg
 
Apr 17, 2020 at 1:26 PM Post #75 of 94

WallofHooligans

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I actually just recapped a set of esp6a's. Kinda kicking myself for not taking pictures of it. I also replaced the resistors. If I knew more about replacing the diodes I would have done those as well.
Can you describe the distortion you're getting? Is it during certain frequencies or volumes?
 

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