I thought the drivers were dust protected by a fine layer of plastic film, so it can't reach the thin space between stator and diaphragm. Reading how it was solved looks like dust outside the driver components can cause the squeal too. Live to learn

Compressed air and Stax drivers do not mix!!! 

 

The film Stax use for dust covers is very fragile so holes in them after some use are not uncommon. 

Damn

Yea, the dust cover is too fragile to withstand compressed air.

Edited October 6, 201411 yr by chinsettawong

The squeal?  Dust or some debris inside the driver making a partial short between the diaphragm and stator causing the diaphragm to oscillate. 

 

I think the problem is not so easy to detect.    My experiance is, that this squeal issue is most on the SR Lambda Signature models, i had maybe more than 10 SR Signature models here and the squeal problem has about 60-70%, the other Lambda models haven´t this issue.

 

Where are the problem, stator, mylar thickness or other!?

The lack of a proper dust cover on the back of the Lambda Signature is the culprit.  It uses the woven mesh but no thick layer of mineral wool to keep everything out of the driver. 

you might have gotten lucky if the problem seems to have gone away and you didnt damage the film.

If blowing compressed air solved the problem, I'm afraid that the dust cover could have already been broken. 

If blowing compressed air solved the problem, I'm afraid that the dust cover could have already been broken. 

 

I have the same worry as well. As a precaution, I've started putting them back in their box when they are not being used.

The lack of a proper dust cover on the back of the Lambda Signature is the culprit.  It uses the woven mesh but no thick layer of mineral wool to keep everything out of the driver. 

 

Thats maybe the reason for this squeal issue, thanks for the hint!    The Signatures has this mesh unprotected on the backside, only some last models of the Signature has the new pvc dust cover of the newer Lambdas and the Pro and the normal bias Lambda has the mineral wool as protect.

Will update this post, got a surprise for some of you guys on a repair the previous owner tried performing on an SR-3 New I'am in the process of re-repairing.

Calling Wink and John McClean this one is for you:

 

http://www.ebay.com.au/itm/Sennheiser-Orpheus-HE-90-Headphone-Amplifier-and-Headphones-/131320287937?pt=AU_Electronics_Audio_Amplifiers&hash=item1e934c92c1

I'm trying to recable my ECR 500 with a Lambda Sig cable but it's not immediately obvious how to disassemble the headphone to replace the cable. Taking it apart has clearly been done before, given Gary's and other peoples' pics floating around the internet. Help?

 

Edit: I can obviously open it up from the driver side by unscrewing the baffle. Then the driver is held into the frame and the long driver tabs go across to the other side.

Edited October 13, 201411 yr by mypasswordis

I have an ECR-400 that I want to do this as well. As soon as I remove the baffle only one side of the white driver assembly lifts up, the bottom side has 3 metal connections secured into the plastic grooves which I assume connects to the cable entry on the other side.

It's been 7+ years since I opened up either of them so I can't remember how you do it.  

 

Calling Wink and John McClean this one is for you:

 

http://www.ebay.com.au/itm/Sennheiser-Orpheus-HE-90-Headphone-Amplifier-and-Headphones-/131320287937?pt=AU_Electronics_Audio_Amplifiers&hash=item1e934c92c1

 

It's a late one so the amplifier will at least work as it should. 

I looked at Gary's pics again (well, a thumbnail since the imageshack servers stopped hosting them), and it seems the way to open them is not through the baffle side, but the outer side. I used my fingers to pry open the metal backside, which was glued onto the plastic housing in two places. You have to be careful not to damage anything when doing so (plastic from the 1970s is not so good), and I have not yet thought of a good way to put the metal backside on without making it permanent. Maybe it doesn't really need anything other than friction.

Will the ECR's work straight away on normal bias or pro bias after a cable swap?

They are electrets, thus only four pins on the connector. Only the TOTL ECR 800 or 880 or whatever was a full blown electrostatic, which seems not to have passed the test of time as well as the ECR 500s.

My google-fu isn't so good and it seems most of Smeggy's old imageshack uploads are gone, what cable connection goes to where on the electret driver? 

I'll leave it to you to ohm it out with a DMM when you open it up.

I'll leave it to you to ohm it out with a DMM when you open it up.

That seems like a difficult venture with an electret.

By ohm it out I don't mean the drivers, but the cable. Should have specified, I find the continuity beeps annoying.

I know the connections from the Stax plug to the end cable leads that attach to the driver. What I meant is since 2 of the connections are used per channel from normal bias cable I have, what is the -/+R/L connections on the electret drivers?

 

I finally managed to pop the hood off my ECR-400.

 

 

 

 

Edited October 14, 201411 yr by DefQon

Hint: the trafo box is unipolar but the drivers are not

 

http://www.head-fi.org/t/157539/sony-electrets/30#post_2062726

Anyway I have an AKG K340 that seem's to be have some noticeable imbalance in the upper-registers which I assume is due to the electret driver. I eliminate the issue of cable or the dynamic driver and the PCB board with the step up transformer by swapping the electret element to the opposite channel, the imbalance issue can back on which ever channel the electret driver was soldered too.

 

Anyway I carefully disassembled it and it's very odd. Using plastic stators there seems to be a plastic film on both sides of the membrane that seals the inside diaphragm which also has it's charge, re-coating both sides like I do with my e-stats that have channel imbalance seems to do nothing. I did come across with somebody from rockgrotto whom had an idea of using a watch battery to somehow charge the diaphragm, spritzer any ideas? (Took these shots a while ago but haven't had the time to upload them.)

 

 

 

 

Edited October 14, 201411 yr by DefQon