The Koss ESP950 thread (ESP owners, please contribute! :)

[AudioCats]

Hello ESP950 owners, why don't we make a discussion thread for the ESP's?

It will be fun!

 

[AudioCats]

So I am officially on the ESP950 boat, just received my pair (phones only, no amp).

First impression: I have to say I am not impressed by the build quality. Very flimsy construction, thin plastic, the head band is too narrow (uncomfortable, and slides around), and the ear pads are super huge and not as soft as they should be (actually doesn't provide a seal around my ears, guess there won't be much bass). Light weight, but because the super large/loose ear pads and the narrow headband, it still feels like they are trying to fall off my head.....

And the MSRP on these is $1000 for the system? ( phone and amp, according to the Koss site)
Since I don't have an amp to drive them, there isn't any sonic impressions. I am trying to finish a transformer box by the end of the month.

 

[AudioCats]

Just because I can't listen to them doesn't mean I will let them sit in a box.....

I am gonna open them up and do some "cleaning and inspection" despite these are basically in brand new condition

Take off the pads, you will see a thin layer of black foam. Lifting the corners of this layer exposes four screws.

Undo the screws, and seperate the baffle from the cup housing. Now we see there is a black protective screen on top of the driver.

Lift out the black screen bracket (this bracket also locks the driver into the baffle). Now we can see the driver, made of clear plastic with silver coating inside, an't that pretty.....

 

[luvdunhill]

another owner here. I removed that felty/sticky foam on mine and felt it improved things. However, make sure you store them properly to avoid dust / arcing, etc. I'm looking for some replacement velour pads, against Spritzer's advice. BTW, I swear Afrikane's He90 had velour pads, by looking at the pics:

http://www.head-fi.org/forums/showth...highlight=He90

I actually like the headband and they have a very tight seal when I listen to them, which is critical for electrostatics.

anyways, enjoy!

 

[luvdunhill]

hm, my drivers look different from yours. Check out my pics in the Stax thread...

 

[AudioCats]

Take the driver out. What the #$%^??? These phones actually use a piece of thin film as dust cover, like them ESL speakers??

Take out the dust cover film, there is a thin black protective screen before we reach the black foam layer (the one you have to peel back the corners to get to the screws).

 

[AudioCats]

Driver connection (this is the right side driver):
Red: inward stator (near your ear);
yellow: bias/diaphragm
Green: outward stator (away from your ear).

 

[AudioCats]

Quote:

Originally Posted by luvdunhill /img/forum/go_quote.gif hm, my drivers look different from yours. Check out my pics in the Stax thread...

Dude, don't scare me that way

I can't really test these for sound so I have to assume they are working.....

How many versions of ESP950 are out there?

 

[AudioCats]

Now the good stuff:
Looks like the Koss wires are double insulated, reminds me of the mini 3-channel AV cable wires, except it only has the center conductor, without the outside coax shield.

The insulation is likely PVC, the green sleeve actually melted when I soldered the wire back to the terminal, it can't be teflon that is for sure. Now they really look like cheap playstation AV cables without the outside coax shield

 

[spritzer]

Quote:

Originally Posted by luvdunhill /img/forum/go_quote.gif BTW, I swear Afrikane's He90 had velour pads, by looking at the pics:

There is velour on the contact surface but the rest is leather. The HE60 pads are the same except no leather only crappy, peeling vinyl.

Quote:

Originally Posted by AudioCats /img/forum/go_quote.gif Take the driver out. What the #$%^??? These phones actually use a piece of thin film as dust cover, like them ESL speakers??

All electrostatics need dust covers, though Martin Logan in their infinite wisdom decided against it

. It's normally a plastic film on the ear side and some fine woven mesh on the other side to lessen any reflections inside the driver.

The cable is very similar in construction to the one Sennheiser used on the HE's with an outer coat and loose wires inside.

Btw. Congrats on the new phones. I was going to bid on that set but I'm glad I didn't outbid you.

 

[AudioCats]

*** The ESP950 plug pin-out (correct me if I am wrong), with the plug pins facing you:

. . A. . B . .
C . . D . . E

A- right side, outward stator (away from your ear)
B- left side, outward stator (away from you)
C- right side, inward stator (near your ear)
D- diaphragm bias
E- left side, inward stator (near your ear).

*** Now the really good part, capacitance measurements. All readings from my 13 years old Fox multi-meter, which is supposed to be accurate within +/- 5%. (to verify that I measured a bunch of 10% and 5% Wima caps, and all the readings were within the specified tolerance/value printed on the caps)

capacitance of stock cable (driver disconnected):
-- between two adjacent wires: fluctuating between 56 and 72 pF, so the average = 64pf. The meter reading was steady when measuring Wima capacitors, I think the cable maybe picking up EMS so the cable capacitance reading is fluctuating.
-- between the inward and outward stator wires, (right side, with the bias wire in between them): flucturate between 34 and 38pF, so I took the average value= 36pf.
-- the cable is slightly over 4' in length.
Does anybody have the capacitance readings from the full size Stax ribbon cables? All I know is the baby stax mini ribbon's spec is 27pf for 6' (then it will be 18pf if it is a 4' cable, the capacitance is exactly half of these ESP950 cable's).

Capacitance, cable + driver combined:
-- between inward and outward stators: fluctuating between 75-81pF, take average = 78pF (This includes the capacitance of the wiring) which is much lower than the Lambda's 130pF......

 

[justhavingfun]

Although ESP/950 phone looks kind of flimsy, it will hold up well if you take care of them. I had mine for over 10 years ( I think I bought it 1995) and it is still going strong although I had to send the phone to Koss for some warranty repair work few years back. One of the driver was making static noise. Other phones came and gone but some reason I am still hanging on to my ESP/950.

 

[AudioCats]

It was easy to find female pins to fit the plug pins, I chop them from an old computer power supply, got that idea from Birgir

 

[AudioCats]

Ok, finally, the cup housing:
If I remembered right, I saw a picture of foam liner inside the cup? this one has just one layer of black non-woven fabric/thick paper/felt/whatever-you-call-it.

 

[AudioCats]

Thanks guys

lets keep this thread growing, make it into another 100 page mega like the Stax thread.... or is that possible?

Quote:

Originally Posted by luvdunhill /img/forum/go_quote.gif I'm looking for some replacement velour pads, against Spritzer's advice. I actually like the headband and they have a very tight seal when I listen to them, which is critical for electrostatics.

Velour pads? from where? actually, if you already have a pair of old worn ESP950 pads, you can peel off the pleather plastic and expose the nice soft velour underneith..... like what I did to my Koss TD60 (left: original; right--plastic peeled off, comfy black velour

)

I must have a narrow head, the 950's look ridiculous on my head....

Quote:

Originally Posted by justhavingfun /img/forum/go_quote.gif Although ESP/950 phone looks kind of flimsy, it will hold up well if you take care of them. I had mine for over 10 years ( I think I bought it 1995) and it is still going strong although I had to send the phone to Koss for some warranty repair work few years back. One of the driver was making static noise. Other phones came and gone but some reason I am still hanging on to my ESP/950.

Thanks, nice to know the 950 will out last other phones

when I said the 950 being flimsy I was comparing them to the other ESP's I have/had (ESP7, 10), and maybe those phones are over-built..... (The ESP7 housing was built like a tank, and they weight like a tank too

)