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My DIY electrostatic headphones - Page 107

post #1591 of 1594
Sure, having thicker spacers increases the possible excursion, but that's about it. I have a feeling the actual limiting factor will be the diaphragm tension. If there isn't enough space for excursion I guess the diaphragm will hit against the stators which must sound rather ugly. And perhaps cause arcing.
post #1592 of 1594

Hitting the stators is a guaranteed arc.  You have to take the voltage breakdown of air (say V/mm for ease) and determine what the max excursion you're willing to allow, keeping in mind humidity (lowers voltage breakdown of air).

post #1593 of 1594
Thread Starter 
If you insulate your stators well, then there won't be arcing even if the diaphragm hits the stator. For headphones, you really want to use the thinnest spacers you can. In my early days, I used 1 mm spacers and biased them upto 1200V. Nowadays I only use 0.5 mm spacer and bias them at 580V. The thin spacers help a lot with the efficiency.

I can play my music as loud as I can take and still the diaphragms are not hitting the stators.
post #1594 of 1594

Hello all.

A few days of pondering and sketching in my note book and looking around for bits and pieces in local hardware stores leads me to some more message reading and more research questions.

 

Quote:

Originally Posted by n3rdling View Post
 

The volume of the cup is pretty large on the HD800.  You may need to use thicker spacers and run at a higher bias to get the bass you're looking for.  Lining the interior walls with the right material will be important to get rid of unwanted reflections.  Sounds like a very interesting project though :)

 

Yes the volume is quite large I agree, however it looks to me as though the Stax SR Sigma also has fairly large boxes for ear cups. I don't know of the Sigma boxes are sealed against the ears but the diaphragm area is about the same as I am thinking for my drivers (The Stax uses 44 mm X 89 mm with 22 mm radius ends - by my measurements anyway - and I propose to use 65 or 66 mm circular).

In the case of the HD800 ear cups i noticed on close scrutiny that the paneled sections of the walls of the ear cups are actually not sealed but full of tiny holes (like a very fine stainless steel mesh I thought). I am wondering whether I would need to do something similar with mine. What do you think?

 

As for the spacer issue, I don't know. I intend to start with 0.5 mm spacers and 580 volts bias from my Stax SRM1 Mk2 amp. The bias is fixed for the moment at least. I propose to use 2 micron Dupont Mylar C but the coating I am not certain of yet.

 

 

Will graphite rubbed into the surface prove more long-lived than anti-static spray or dish soap or fabric conditioner?

Quote:
Originally Posted by NoPants View Post
 

I like the idea of the project from an aesthetic point of view, but I imagine a fair amount of difficulty achieving the desired fidelity. Are you hoping to get the benefits of the SR-Sigma in an HD800 package?

Yes, I suppose you are right - I am! The SR Sigma sound stage though, by all accounts, is uniquely huge and up front. I don't suppose I will be getting near that but I will try for a sound stage wider and more forward than I currently get with my Audio Technica woodies and my Senn 565s. My woodies actually have a very good wide sound stage (maybe because they also use slightly angled drivers), so I will be trying to better them really.

 

What sort of difficulties do you anticipate I will come across?

 

I am asking knowing very well there will be plenty of challenges. What I am hoping for is that by attempting to make my driver similar in shape and size to the HD800 I might have something that already sounds pretty good. Do you follow my thinking?

 

 

Since I don't have my own set of HD800s, I am trying to locate some drawings or get some dimensions of these headphones. There are plenty of photographs to be studied of course and I have amassed quite a few of those and measured off them as best I can. 

 

Does anyone have any such measurements? or drawings? (a strangely unique question I guess!)

 

I have estimated from pictures that the drivers are tilted at an angle of 8.6 to 8.7 degrees from, shall we say, 'flat', that is, parallel to the side of one's head.

The ear cups look to be about 110 mm outside vertically from apex to apex (corner to corner? ) of the otherwise round ear cup shape. 

 

So many questions I seem to be generating...

I have to say that this is a marvelous place to come to and explore and I really do appreciate everyone's helpful comments. None of this would be remotely possible for me to attempt without it.

 

Cheers all anyway. Time for me to get some shut-eye now...

 

urlgr-A


Edited by urlgr-A - 10/29/14 at 9:21am
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