[wppk]

I took some and will send them
But you will not find them in perfect shape, as i dismenteled them so often to find solutions, the least thet one can say is that they are not brand new... I have been working on them for weeks and hours.
so, I found a rather acceptable imbalance, now, using other drivers that were in better shape. it is not perfect but will do for the moment.
I have several observations that may help other people facing the same problems as mine.
first, I have to say that on all of my cans, normal or pro, I removed the black upper rings, with a grill, because letting them on lowers a lot the quality of the sound it you keep them on. Normal, because it makes an important screen. But, I think this may be part of my problem,  cause I believe now that it also protects from temperature.and possibly, magnetic field.
After you told me, wachara, about the outer damping ( your pictures) I made a lot of different tests that led me to notice that I could'nt make an evidence of it to discharge the membrane, even if of course I believe you but it doesn't happen on my faulty cans. remove it or keep it will not change anything. But I could make one thing sure: the proximity of the ear discharges the membrane or, any way, lowers the sounds even until il cuts it. After a few seconds of letting one can on one hear, it extinguishes it. and the sounds totally gets back after the same while.
as, for my so many assembling and disasembling, I couldnt have an anti condensation membrane at all my tests, I saw that. Because after having put one onf these membranes, I had no more sound fading.
But even so, and even if I I could make a good balance with both cans as long as I didn't put them on my head, the balance changes when the drivers are correctly set into the housing, but you can only really hear the difference and then, imbalance once the cans are on your head. Which, as you can easily guess, is very disappointing, when you think you had finally found the real solution, after putting all screws back for the tenth time.
if anyone has a handkerchief ( antistatic please) to send to france for the tears I shed, it will be apreciated.
Also, something I can figure out is when I plug back both srx pro on my amp (trm t1). it ils not easily observable nor permanent, but the imbalance of one imbalances the other. And not all cans to the right or to the left. When I plug in the perfectly working srx, there is no imbalance. but when I plug the other, an imablance can appear or leave after a wile, and is also hearable in the other can, which also can reach perfect balance at other times.
If only the good can is plugged in, I can't remember to have met the same issue.
the imbalance is most of the time quite subtle, can be corrected on the balance knob by changing just three minutes or five if the knob was a clock. But on the wrong can, it can go up to a 12 minutes change. This is very obviuous to hear with these srx pro, with which you feel any odd thing in the sound so well. That is why it makes them so good for monitoring
so, I think my problem comes form drivers that could be a bit tricky, and from the difficulty to control the distance from the driver to the ear and the temperature/condensation.
I cannot explain here oll the tests and tries I had with these. But I can add I put O rings inside the metallic cups, close to the driver ( side of the ear) to make a little bit longer disance. And it works, but it is not very stable.
BTW , the odd noises, tikks and tongs went away when I changed the body of the driver.
Wachara, you didn't tell me, are there pro versions /drivers for the cans you fixed ?
thanks to all

 

[wppk]

 

here are the drivers, one side per photo.  )
wachara, do you know what are the long resistors-like components that are soldered on the normal bias drivers to + and -, (and not on the pros) for ? I didn't take picture, but I can if you whish?

 

[Muamp]

Hi wppk,
 
I know you addressed the question to Wachara, but I may be able to give two possible answers.
The resistor like components are either:
 
1. The resistor like components are in fact resistors, very high valve Rs, in the order of 10M +... The SRD5s etc were designed to be driven from transformer energisers. With transformer energisers it was good design practice to use high value resistors on each stator in order to make the capacitive load predominantly resistive. The value of R being greater than the reactance of the capacitive load at HF. The reactance of the C seen on the i/p of the step up transformer becomes less than one Ohm at high frequencies making it very difficult to drive. This is because the transformer i/p impedance is related to the square of the step up ratio. This design theory is very well explained in Frank Verwaals free PDF book (http://home.kpn.nl/verwa255/esl/ESL_English_2011.pdf). The resistors remedy this effect.
 
2. Having said answer #1, they could just be insulated wire links. After all, if this was the case, it would have been better to put the resisors as close to the tranformer o/p terminals as possible.
 
David.

 

[wppk]

Hello muamp.
thank you very much for your explaination. I am afraid this it way too technic for me, it I try to get deep into it. But I understand the general meaning. and the effect.
You were absolutely right to answer, Wachara is very busy, but always very friendly and helpfull, as you surely are too, and I thank you both very much for your time.
If I read you well, and catch it better than at the second or third first reads, does it mean that if I use the srm t1, which is not a transformer amp if I am not mistaking, because it has to be plugged to the home electrical alimentation ( sorry for the terms I use, I guess they are not proper in english but may keep understandable, if not, tell me) the resistors are not necessary anymore ?
If I am still right, a transformer energiser doesn't need to be electrically fed that way, the amp on which it is plugged is enough, right ?

 

[wppk]

 
Here is the resistor (in blue). I didn't solder it, just put it where it was

 

[Muamp]

Hi wppk,
 
Yes, if you are not using a Stax style transormer energiser that Stax would have designed to be used with these ESHS then yes you are right, you would not need the resistors. In fact, if you use a solid state or valve energiser then you definately do not want the resistors on the stators. The resistors would probably render the ESHS quiet or silent in a non transformer energiser.
 
Modern designs of ESHS's would not use any resistor in this manner, even if a transformer energiser were to be used. As it would be a much better design to incorporate *ALL* the circuitry in the energiser and have the headphones  as pure panels.
 
David.
 
Edited, Just seen your last post with the new photo. This makes it different. This component could be (need to look up my transformer notes for the name) a way of stopping over-voltage on the stators - voltage limiting on the max Pk-Pk of the stators. On transformer energisers the amplifier feeding the transformer could drive the panels far too much, leading to voltages too great across the stators. This stops the over-voltage.

 

[wppk]

Ok David
(BTW my real name is Luc, nice to meet you ! ) 
I understand very well.
Just one point : I tried with or without the resistor, plugging the sxr in my valve amp, and it doesn't change anything to the sound.

 

[wppk]

I have both energisers, with or without transformer.
what was surprising to me was to see that all the drivers for normal bias of the srx had this resistor, and none of the pros

 

[Muamp]

are the pros designed to be transformer driven   or   solid state / valve driven?
 
David.

 

[chinsettawong]

I have only seen the resisters used in electret headphones.

 

[wppk]

the pr'os ans the normla sxr and gammas can work on both amps, david. the resistors on the pictures were on srx normal bias, wachara

 

[wppk]

Hello David
hope I am not disturbing or mistaking, but you say
Having said that they do sound very good with the mesh. The mesh is good enough to keep out all dust, so no Mylar dust shield needed.
I am not a headphones builder but repair tehm on what I can do, and this mylar shield seems a must have to me, because it prevents the micro condensation( form our head and ears)  from getting on the stators and creating squeak noises.
the mylar membranes don't affect the sound, oddly.
but if you don't use some, I m afraid you are going to experience weird noises. You will notice them after a while of wearing the headphones, and they will leave after a few minutes without the headphones being on your head.
also, being french, I am not sure of the meaning of mesh. If it doesn't let humidity pass trough it, then mylar will not be needed of course

 

[wppk]

for my repairing : If have ordered julez's advised product to coat the membranes, as I cannot find another solution for the moment . Will see if it changes something.

 

[Muamp]

Hi Luc,
 

 Hello David hope I am not disturbing or mistaking, but you say
Having said that they do sound very good with the mesh. The mesh is good enough to keep out all dust, so no Mylar dust shield needed.
I am not a headphones builder but repair tehm on what I can do, and this mylar shield seems a must have to me, because it prevents the micro condensation( form our head and ears)  from getting on the stators and creating squeak noises.
the mylar membranes don't affect the sound, oddly.
but if you don't use some, I m afraid you are going to experience weird noises. You will notice them after a while of wearing the headphones, and they will leave after a few minutes without the headphones being on your head.
also, being french, I am not sure of the meaning of mesh. If it doesn't let humidity pass trough it, then mylar will not be needed of course

Edited by wppk - Today at 11:13 am

No, you are not mistaken. On my test panel I took out the outer Mylar dust shield and replaced it with very fine wire mesh. The main purpose was to provide an outer protection to the headphone panel. That is, to stop fingers from prodding and poking the panel, even though the panel is fully insulated with the FR4 fibre glass and acrylic spray. But it seems that the mesh is so fine it actually stops all dust from entering the panel (obviously the HV attracts dust and it is the dust which causes the notorious 'squeal'). It is very effective at providing protection and a bonus also effective as a dust shield. The mesh does not protect against sweat or condensation, but the mesh is only used on the outside, not on the ear cup side, which still has the Mylar dust shield. Also, all my ESHS designs use fleece ear cups which are 'breathable' and allow the listener to use for extended periods without any sweat build up that you would get with leatherette / leather / suede ear cups. I am happy with the wire mesh and I will try it on my Muamp #3 design, but my only concern is that since the mesh is only 39% open area (according to the suppliers data sheet) it may be too 'closed' for an open back headphone. Then,.... I notice so many production ESHS including Kingsound have very low open areas in their panels......
 
David.

 

[wppk]

okay, that is clearer to me. sorry, cause I suppose I let you repeat somethnig you had said already. I will probably let your repeat something else or well known by evryone here, but what is the HV ?