[chinsettawong]

It's now clear that they are electret headphones. The electret headphones don't need a bias voltage on the diaphragm. They use a different type of material for making the diaphragms. I have no knowledge of what type of material that is though.

 

[wppk]

Ok, thank you anyway

 

[Julez]

  Try Licron
 
Have any of you tried making a quadraphonic headphone?

Hi 100VoltTube
 
thanks for the tip with the Licron Crystal! It works fine! It is also less prone to dust issues. Altough it is easy to apply too much and get coating that's too thick. But I have managed to get the right thickness by using a sponge that I dip into the liquid and squeeze it hard afterwards. The coating is then barely visible and works fine. Otherwise I had the feeling it is too heavy and the resolution of the drivers is lower than the original Stax drivers. It is heavily sticking to the membrane wich is a very good thing! But no chance to wash it off and recoat the driver if applied too much. At least not with isopropanyl or water.

 

[wppk]

Hi you guys !
A frenchman has read what I have written on this post for the mending of the stax lambda I tried. his lmambda was ill balanced, and he was asking for help. He seems to have quite a good knowledge of electronics and he is mending his membrane ( the sounding one, not the protective one) he will tell me news I guess. if you are intersted, I will tell you here, because he says that he has mended it, and that is still working now, with no change. It then interests me a lot !
I also am saying that here because he give me a link to a very interesting page, here http://www.asrr.org/biblioteca/Revue%20Audiophile/fichiers2/03/casque.html form philippe Hiraga, an HIFI expert in france, whom yous probably have heard about. In there, he says how to make electrostatic headphones , and you know thet your post is read by people all arount the world. It will obviously interest some french people, who can't read you in english. there is a strange % sign in this link, the link works with my computer, but it could be useful, if it doesn't work on your, to remove it and try this then  :  http://www.asrr.org/biblioteca/Revue20Audiophile/fichiers2/03/casque.html
if you need further explainations on this document, I can translate parts of it, but probably not the whole.

 

[DaveK1977]

Well, I'm back and I finally have a pair working together that could fairly be called a pair.  I can't wait to mount these in a set of headphones and see what they really sound like.
 
The audio on this video was recorded with a Tascam DR-05 held close to the drivers while they were playing.  For the last few seconds of the video, I let the audio recorded with the video play through.
 

 

[Muamp]

Hi DaveK1977,
 
I like the round steel stators, how did you cut them?
And tell us some details....
Spacer thickness? Diaphragm material?
Are they square openings with round stators? open area size?
I cannot see any fixings holding the stators together, how are they fixed?
 
David.

 

[DaveK1977]

I'm shaking right now, because I put together a scary pair and put them on and got away with it.  I would have told anybody else not to put it on, but I just had to.  They sounded fantastic.  No regrets.  There's another message coming, but I'll reply to the questions because they're good and will it all easier to share.
 
 

I like the round steel stators, how did you cut them?

I had a man cut them for me, but it hasn't gone perfectly.  I found a listing on eBay for a stainless steel sheet like I wanted, and asked if the seller could cut them for me.  I measured everything metric because the Superlux foundation I was using was made in China and copied a German design, so I knew it was built in mm and should be measured that way.  He cut in English units and they're a bit big.  I will have to scrub some stuff down on the headphones before they'll fit in the cups, but if you're in a metric country, you might do better with that.  An 85mm disc will neatly replace the driver and baffle plate in a Superlux HD-330, and I guess it could be done to a Beyer DT if you had a dead one.
 

And tell us some details....
Spacer thickness?I cannot see any fixings holding the stators together, how are they fixed?

The spacer is 3M VHB tape, seen in the red rolls in the video.  It's 1.1mm thick.  That's also what holds the sandwich together.  You can buy it in auto parts stores as this variety is sold for attaching emblems to cars, and it's strong.
 

Diaphragm material?

Ultrafilm Mylar, designed for indoor model airplanes.  1.4 micrometers.  Weighs very little.
 

Are they square openings with round stators? open area size?

Yes, the openings are square because it's easier to lay out the tape that way.  They're about 25 square cm.
 
I didn't have my Staticide at the house, so I used Static Guard, a spray for clothing for a coating.  I'm hoping that the Staticide coating will up the volume a little. 

 

[DaveK1977]

Ok, so I got impatient and had a listen tonight.  Only one song, so as not to tempt fate, as this wasn't a commercially ready pair, let's just say.  I had to know, and they didn't bite me.
 
I wasn't quite sure what to expect them to sound like, as it's hard to judge from the measurements and recordings that I made the day of the video.  Obviously they worked in the open air, but they had an obvious upward creep above 12k that really I was afraid of.  At the very least, I thought they might reveal some detail, but I wasn't sure they would be possible to enjoy.
 
They sounded really amazing.  There was no apology needed for the sound or response. It really sounded balanced and normal, which was definitely good.  I can't try to build a different pair until at least Saturday, so I'm going to shock proof a bit more and try to really listen for a while tomorrow night. 
 
They weren't loud even turned all the way up.  It's patched together with poster putty, and the drivers don't fit in the hole as outlined above.  There's leakage and dubious diaphragm coating.  I'm sure that by the time that everything fits right and Staticide is coating, they'll be louder.
 
Keep in mind that this is the first time that I've ever listened to a pair of electrostatic headphones, and I made the drivers.  I'm sure my opinion is rosy, but I was blown away.

 

[chinsettawong]

Hi DaveK1977,
 
First of all, congratulations on your successful build.  I remember exactly how much joy I had when I successfully made my very first pair.  They just sounded so good that I kept listening all night.  I'm sure you're feeling the same.  
 
Your perforated metal is OK for making the stators, but please remember to do a good coating on them.  You need a very good insulation on the metal.  Otherwise, you might get an electrical shock if you're not careful. 
 
Double sided tape is alright for spacers.  However, the thickness of 1.1 mm is too much.  You can't really get louder sound from using Staticide.  You can achieve it by either using higher bias voltage or thinner spacers.  Are you using step up transformers or are you using a direct drive amp?

 

[Muamp]

Like Wachara C. says, the spacer gap being too big is the most likely cause of low volume.
I used to use steel stators, but I cut the steel with a normal hand held jig saw into hexagonal stators. In this way it is very easy to cut and fits over spacers really well (hexagonal or round). I also used to use neoprene spacers with spray glue to hold them on the spacer. The neoprene was slightly less than 1.1mm but still too thick.
 

The spray shield was to stop the glue being sprayed onto the stator when applying the Mylar.
 

 
These were made nearly two years ago. You can get a good finish with Acrylic spray paint.
 
David.

 

[wppk]

I know this is not an electrostatic mending, but it is the following of what I previously wrote, and it is DIY. So, it still has an interrest, I think.
I repaired my bisset, because the original driver is unfindable, and another item like this one seems too. I ordered this http://www.ebay.com/itm/121314870113 and used them as drivers in the Bisset/Stax. The result is really gorgeous ! It is very comparable to me srx mk3, with a little bit more bass.
I am very happy to have found this solution, and I hope it can help people who can't find original drivers like me.

 

[DaveK1977]

What would ideal thickness be?  I thought that this was similar to the spacing of factory built ones.

 

[chinsettawong]

Haven't you read the thread?
 
The ideal thickness for the active area of up to 80 mm is around 0.5 mm or less.
 
It's a challenge to get the right tension with that spacer thickness though.

 

[Muamp]

Most DIY'ers on this forum use 0.5mm thick spacers (each side of diaphragm) for ear speakers.
I use 0.5mm FR4 (copper clad PCB material), as do many others.
The thinner the spacer, the more sensitive the driver, and therefore also louder. Higher frequencies in the audio range stretch further as well.
When I used metal stators with 1.0mm spacers, the bass was very strong (too strong for me) but the higher frequencies were lacking.
I believe some of the Stax go as thin as 0.4mm, but I have only got this information from other posts in Head-Fi.
 
David.

 

[DaveK1977]

Yeah, I've read the entire thread, but it's actually been a while for most of it.  This experiment has had some false starts and is a long time coming, but the results already were better than I had hoped for the first sample.  I was expecting a screechy sound with very little bass, and found instead a very natural sound.  I'm still experimenting, and I'll probably continue to do so.  Wachara could've stopped after his pairs were validated by Tyll's tests but clearly hasn't, and I'm sure that I'll be playing with this stuff for a while.  Easy to get basic function, but so hard to perfect.