My DIY electrostatic headphones - Page 15

Quote:

Originally Posted by spritzer 

My issue was getting consistent results when people have no experience stretching and gluing mylar.  This would be a 100% DIY project but I believe that it isn't worth the bother if anybody with the minimal skill and basic instruments can't build it.  It also prevents Kevin and I from going way too deep down the proverbial rabbit hole...

 

 

I will think of a simple and effective way to stretch and glue Mylar for you.  I actually have an idea.  Let me go back and do some experiments and I will post a step by step procedure with pictures for you.

Happy New Year!

Wachara C.

Hi Birgir,

That surely is one of the simplest and effective ways to tensioning Mylar.  There is another way that I would like to suggest. In this case you use a piece of glass and predraw some scales on it.  Let's say for each 1 mm you draw a line.  You cut Mylar just big enough to make a pair of headphones.  You tape the four corners of Mylar on the glass.  Draw a line on Mylar to indicate your prestretch starting point. Then you hand stretch your Mylar to your target point by observing the line on Mylar against those on the glass.  When you get to your target point, you simply tape it down. Do the same for all four sides of Mylar. I have some pictures below to show what I mean.  It's basically the same principle of how I stretch Mylar for my ESL.

These pictures are taken when I use a rubber tube tensioning jig for my ESL.  It's the same principle I use here.

As for gluing Mylar, I haven't found anything better than rubber glue.  I use a piece of sponge to help me apply the glue evenly.

This is how I tape Mylar.  I use a soldering iron for cutting Mylar. 

Usually, I will cut a few more pieces of spacer rings. I like to try with different tensions and different thicknesses of Mylar.  :)

Wachara C.

Hi Birgir,

With enough mechanical tensioning, there is no need to use another heat treatment on the diaphragm.  On ESL building threads, there have been a lot of discussions about this topic, and it's pretty apparent that you can only heat shrink the diaphragm to a certain extend.  However, mechanical tensioning can do a much better job than heat. 

I don't think that the diaphragm is to blame for when the diaphragm looses it's tension.  Most of the times, it's glue that fail.

And yes, Quad did use an oven to do a heat treatment.  But, I'm skeptical about that.  They could have used heat to treat the coating material and not the diaphragm.

Wachara C.

Here is an example of a failed ESL driver.  When I opened it up, I found that the double sided tape that I used gave up its strength.  This was after about 3 months of usage.  When it failed, the diaphragm would collapse to one side and the sound was very much distorted.

The diaphragm was initially stretched to 1.5% elongation on one side.  It's probably too much. 

Wachara C.

Hi Nixon,

Your design looks great. However, you also need to have a knob on your stator so that you can solder the + and - audio signal onto. 

What is the spacer thickness you intend to use?  I assume that you are going with 70 mm active diaphragm area, right?  In my last design, that is exactly the dimension I use.  But, if I were to do it again, I will increase the active diaphragm area to 80 mm.  This will give you better low frequencies response.

Wachara C.

That stator design looks interesting.  But I think that your long and unsupported opening will cause you problem.  The whole stator might not be strong enough.  You might want to reduce the length of your slots down to perhaps 2 -3 cm, IMO.  Otherwise, it looks really nice.

Are you going to use a PCB to make your stators and spacers?  Don't forget to etch out all the unneeded copper on the outer circle of your stator.  With the copper out, it really make a huge difference in high frequencies response.

Wachara C.