[cjfrbw]

It started out some months ago with the sound breaking up in one channel.  Then, the sound became more or less balanced, with the problem in both channels.  This would tend to indicate some kind of bias problem. Yes, they become less loud as time goes on, compared to the efficiency when they worked correctly.
 
However, if the headphones respond differently to a known good quantity i.e. the SRD 7SB, which I know is good, it would indicate the problem is with some kind of time dependent short in the headphones somewhere, or a poor contact etc. etc.  
 
I.E.  bias charges, stators sound fine.  Over time, stators sound worse, plugging it back into known good bias source 7SB, sound is worse.  Sounds like a scratchy, intermittent low quality transistor radio, not Stax.

 

[wink]

I think that you don't seem to understand the bias voltage and it's effect on the headphones.

 

[cjfrbw]

Well, thanks for the contributions, and I am sorry for wasting everybody's time
 
I endeavored to take them apart and look inside, and the mylar bits on both right and left sides have holes.  I guess it arced at some point.
 
I now surmise that they got wet, and when played, the moisture caused them to arc and perforate the mylar. Or some other disaster. I suppose the bias units were OK all along, but now I wonder how they ever played at all OK for any length of time. I guess the mylar must warm up or soften or something and the holes then cause the noise.
 
Now, the question is, where do I get replacement mylar parts.  It looks like I can replace the part myself if I can get two of them. Everything else on the headphone should be OK.

 

[wink]

Those are dust covers.
They shouldn't affect the sound of the phones, except in dusty or very humid conditions..

 

[cjfrbw]

The dust cover has been removed.  The picture shows  the mylar attached to the bias conduction ring, underneath the top stator.

 

[chinsettawong]

Believe it or not, even with holes on the diaphragms, the diaphragms can still produce nice sound. How is the condition of the dust covers? If your dust covers have holes, the moisture from your face can go inside the driver and eventually condenses into tiny drops of water on the diaphragms. It takes a few minutes for that to happen. When it happens, you hear funny noises and the music can sound distorted.

The good dust cover is only very crucial on the side that is facing your ear. So if it has holes, you should change the good one on the back side to this position.

If you want to try to change the diaphragm by yourself, you might get some useful information here: http://www.head-fi.org/t/498292/my-diy-electrostatic-headphones

Wachara C.

 

[cjfrbw]

Hi, Wachara,
 
I think I will try to replace the mylar myself.  I don't see any place where they sell just the bias ring and the mylar part.  The parts are just layered into the 507.  It looks like with ES headphones, learning to replace the mylar may be an essential skill.
 
I will pursue the site you stated.  It looks like three things, the mylar and some tape to stretch it, glue and some solution for electrifying the membrane.
 
I think that is within my skill set.
 
Regards,
Carl

 

[spritzer]

Sucks it was the headphones that were acting up and not the bias supply. 

  I for one would contact Stax about this though as 507's seem to be dropping like flies these days and they might just replace the drivers at a lower cost or something like that.  There is clearly something wrong with these new drivers as the older number series didn't have these issues. 

 

[FrankCooter]

Quote:

  I for one would contact Stax about this though as 507's seem to be dropping like flies these days and they might just replace the drivers at a lower cost or something like that.  There is clearly something wrong with these new drivers as the older number series didn't have these issues. 

 
This is very distressing news. Care to elaborate?
 
My 507's are about a year and a half old, and to date have had no problems besides the usual cup/frame separation issues caused by the pathetically undersized mounting screw.

 

[cjfrbw]

Ping 

chinsettawong

 
Is this product sufficient for what you were using, i.e. Staticide 6300, to electrify the mylar surface?
 
It comes in a spray bottle.
 
http://www.all-spec.com/products/ACL6500.html

 

[chinsettawong]

That's more than enough.

Wachara C.

 

[cjfrbw]

OK, I bought the stuff.  1.4 mylar sheeting, glue, and the Staticide 6500, all about $65 delivered.  If it works, better than shipping headphones to Stax or its agent, arguing about whether it is their fault or mine, getting a whopping repair bill plus shipping etc. etc.
 
Probably enough stuff to repair 30 507 headphones, but no other way to get small quantities.
 
If the native Stax mylar in the 507 is that bad, could this be worse?  Guess I'll find out.

 

[spritzer]

The main problem will be to get the correct tension on the film and heat treat it once you are done to anneal the plastic and lock the tension in place. 
 
Quote:

 
This is very distressing news. Care to elaborate?
 
My 507's are about a year and a half old, and to date have had no problems besides the usual cup/frame separation issues caused by the pathetically undersized mounting screw.

 
This is only based on the PM's I get which clearly point to some issue with the sets.  I tried my old set last week and it is still perfect but I'll try and collect some more data on this and then annoy Stax. 

 

[cjfrbw]

Well, now that I have set myself up, I will document my (success/ spectacular dummass failure).  Usually, just waving a soldering iron close will do some heat treating, but not with the industrial uniformity of the manufacturer.
 
 However, I often wonder how uniform the manufacturers are to begin with, usually one just wants a pair that were made at the same time to approximate uniformity.

 

[spritzer]

All Stax drivers are measured to a fixed spec so any that don't meet it are tossed.  That's why a Lambda Pro made in 1982 sounds the same as one made in 1990. 
 
For proper heat treatment you need an oven but a heatgun would do in a pinch.  I only shrinks a few % but it's easy to notice when it has set.