[chinsettawong]

Hi Steve,
 
Here are my answers to your questions:
 
1.  I don't really have the target tension for your diaphragms.  You just have to try it by yourself.  If you have too much tension, you'll have less bass.  If you put too little tension, then the diaphragm will collapse to one of the stators.
 
2.  The target resistivity is anything between than 10 - 100 M ohm per square.  But if you don't have a high voltage multimeter, it can be quite difficult to measure.  
 
3.  Rubbing graphite on  the diaphragm can be tricky.  But if you think that you can do a good job, just go for it.  I'm sure that it'll work just as well.
 
4.  Can you take a photo to show how your spacers are like?
 
Wachara C.

 

[quintile]

Below is an picture of the stators an the diaphragm support ring.

the stators are metal grids held in a plastic ring. the inner surface of one of these is flat, but the other has a recess into which the diaphragm ring fits. this has the effect of tensioning the diaphragm as the two stators are pressed together.

Note the small holes in the edge of the three items. These allow sprung wires to connect to the three elements.

The stators are held together with a small strip of adhesive tape around the edge of the two stators.

I have tried assembling a new diaphragm with 1micron Mylar using UHU POR glue and Teknis epa anti static liquid. http://www.teknis.co.uk/p-1114-epa-surface-cleaner.aspx

I was very pleased to get a conductivity, after gently rubbing the diaphragm, of 10nS = 100M ohms.

I failed to get sufficient tension first time, even after heat shrinking it, but I will keep trying.

-Steve

 

[sutsug]

I repaired my Micro Seiki with cellophane and 'wood glue' and 'charcoal' from an artist pencil. Cellophane stretched out with tape on a mirror. Charcoal rubbed on paper sticks to your finger. Dip it in a wood glue/water solution and rub it on the foil. Glue the rings on the foil with wood glue. Cut them out loosely with a scissor. Melt the excess foil and hole and 'bald spot' away with a soldering iron. It worked the first time (except for some whistling that disappeared after a few days. Maybe moisture) but I do miss a full bass-sound.

Schematic Micro Seiki: http://postimg.org/image/thycx8uy9/full/ They say it was made by Stax but it uses only four wires to the headphone. Inside box: http://s13.postimg.org/wl8tmvuqv/microseiki_623.jpg

Something else: I disassembled a Samsung Microwave (warning: deadly voltages even unplugged) and found this behind the window: http://postimg.org/image/lx36upf4j/ A beautiful 0.5 mm thick sheet mesh!

 

[quintile]

Well, it all worked rather well.

Thanks for the pointers to schematic.

using the ESD fluid worked well, but I am a bit disappointed by the lack of real bass.
I wonder if the problem is excess diaphragm tension?

I pul the diaphagrams in orientated so the tension is increased when the stators are put together.
I may try reversing them. I glued the diaphagrams to the rings under a little tension, though not much.

I was very pleased to find that Bose quiet comfort QC-1 headphone EarPods fit the micro seiki
Headphones -they are a bit of a tight fit but they work. (I bought them on eBay from China of course).

I am going to try and measure the diaphagrams resonance frequency with a cheap microphone,
I think this may indicate where the LF roll-off may begin.

If not the diaphagrams tension then I guess it's just the driver area that is limiting the of response, I
Am already using the lightest diaphragms I can find 1 micron.

If anyone has any other suggestions of what limits LF response, I would be very interested.

-Steve

 

[CosPhi]

Hello
 
I have some minor question regarding the perforation of the stators. You're using a triangle-based tile, which gives a higher efficiency for empty/total area, and also, somewhere in this long thread, there was someone saying that the best/maximum ratio should be 60% (opened area vs total, if I got it right). OK so far, but, from what I see in the pictures all over the thread and mostly "ogling", it shows that the holes are (in general) 2mm diameter and the spacing is (looks like) 1mm. If I am wrong, don't read up the next part
 
Before I go on, I've tried my hand in some basic geometry and came up with this formula for "x" in the picture: http://tinypic.com/r/102r1cl/9 (can't upload here):
 
2 * r * { sqrt[ pi/ratio) ] * 1/3^0.25 - 1 }
 
or, more simplified:
 
r * [ 1.905/sqrt(ratio) - 2 ]
 
The ratio is not the percentage but the brute division, as in for 50%, ratio=0.5. This gives the dimension of the spacing required to meet a certain ratio. So, for a 60% opened area and 2mm holes, ratio=0.6, r = 1mm =>
 
x ~ 1 * [ 1.905/sqrt(0.6) - 2 ] ~ 0.46mm
 
This can be easily verified with the reverse formula:
 
ratio = ( 2 * pi * r ) / [ a^2 * sqrt(3) ]
 
where a = 2 * r + x , which (again, ogling) => ratio ~ 40.3%. Even for a 50% ratio, x should be ~0.7mm, not 1mm.
 
So, at this point, I'm confused: either the ratio is exaggerated (or I got it the wrong way), or the ratio is good and my ogling should know better. Can someone please provide some measurements for the holes on their stators (and a clarification for the ratio)?
 
 
Thank you in advance,
Vlad

 

[chinsettawong]

Hi Vlad,

I don't think that we are aiming for anywhere near 60% open area. For all my stators, I am aiming for about 40% open area.

I have tried stators with higher open area on my full range ESL, but the stators are too weak and need supports to help with the stiffness. The more open area stators do sound very nice though.

On commercial headphones such as Stax's, the stator holes are much smaller. I don't know what their open areas are, but I don't think that they're more than 40% either.

Wachara C.

 

[analogsurviver]

Hi Vlad,

I don't think that we are aiming for anywhere near 60% open area. For all my stators, I am aiming for about 40% open area.

I have tried stators with higher open area on my full range ESL, but the stators are too weak and need supports to help with the stiffness. The more open area stators do sound very nice though.

On commercial headphones such as Stax's, the stator holes are much smaller. I don't know what their open areas are, but I don't think that they're more than 40% either.

Wachara C.

Something like that.
 
The most open stators I remember were those built by Sanders in late 70s - piano wire rods all across the surface, with every second wire removed - and that yields less than 50 %, once the clamping periphery and some stiffening across the rods is applied. 
 
If it were possible, AKG would have gone with electrostatic principle for the K-1000 ; as the design requires as acoustically open driver/baffle, they had to invent a dynamic driver with more than 70% acoustic openess.
 
The aichile's heel of electrostatics is their stator mechanical resonances. Flick any ESL with your fingernail - what it results in sound, is what should have never been there in the first place.
 
Perhaps time to re-invent/re-use conductive fabric stators a la Sennheiser Unipolar series ?

 

 

[jgazal]

The aichile's heel of electrostatics is their stator mechanical resonances.

What are the natural resonance frequencies of a stainless steel stator, a quartz glass stator, a ceramic compound stator and a FR4 PCB stator?

Can one speculate that natural resonance frequencies of a stainless steel stator are in the treble and mid range while from a FR4 PCB stator are in the bass and mid range?

If a signal coherent with the natural resonance frequencies of a peculiar stator is synthesized and played, how many dbs come from the diaphragm and how many come from stator resonance?

 

[analogsurviver]

What are the natural resonance frequencies of a stainless steel stator, a quartz glass stator, a ceramic compound stator and a FR4 PCB stator?

Can one speculate that natural resonance frequencies of a stainless steel stator are in the treble and mid range while from a FR4 PCB stator are in the bass and mid range?

If a signal coherent with the natural resonance frequencies of a peculiar stator is synthesized and played, how many dbs come from the diaphragm and how many come from stator resonance?

It is the composite - a clever electrostatic driver design uses the necessary evil, the clamping surround, also as means of damping of the stator material(s). 
 
It is not how loud the unwanted sound is  - but the quality of that resonance, mechanical Q is important. If the driver rings - no use of  in theory superior driving principle.
Please see the measurements for Stax IEMs - smaller, better than its larger siblings ! And there are dynamic drivers that can top even that ...- some are actually capable of the proverbial "stopping on the dime"...

 

[CosPhi]

So then, from your replies, I got it wrong, it's 60% closed area, not opened, but the more opened area the better, provided there's enough material strength in the stator, and the stator is as plastic (as in not elastic) as possible. Which is much like asking for a Cauer filter with a Bessel phase... Well then, 40% opened area isn't so bad.
 
Vlad

 

[analogsurviver]

  So then, from your replies, I got it wrong, it's 60% closed area, not opened, but the more opened area the better, provided there's enough material strength in the stator, and the stator is as plastic (as in not elastic) as possible. Which is much like asking for a Cauer filter with a Bessel phase... Well then, 40% opened area isn't so bad.
 
Vlad

My friend coined the best one:
 
We all like our sports bulldozers with low mileage - for free !

 

[Nemeske88]

I don't know if I am posting to the correspondent forum, but I am asking the following:
I have read once that there is a significant difference between SB (Self-biasing) and non-self biasing transformers regarding the sound quality.
 
I am asking if this information true and if yes, can anyone tell me in which aspects one can percieve the difference?
 
Thank you for your reply in advance

 

[analogsurviver]

  I don't know if I am posting to the correspondent forum, but I am asking the following:
I have read once that there is a significant difference between SB (Self-biasing) and non-self biasing transformers regarding the sound quality.
 
I am asking if this information true and if yes, can anyone tell me in which aspects one can percieve the difference?
 
Thank you for your reply in advance

It all depends on RC time constants. 
 
SB (self biasing ) transformers contain LOTS of batteries in series ( till you get to that 580 V for Pro models - do the math...) - and therefore their bias supply is the most stable of them all - veeeeeeeery slowly this voltage is dropping due more to the self-discharge of batteries than anything else - even real world capacitors like headphone electrostatic drivers, have next to infinity resistance and therefore next to no drain.
 
RC constant of the ES drivers should take care of any ripple that gets trough in any AC powered bias supply; and although this ripple can be made small, it can not be reasonably (and safely....) made totally insignificant. Generally, this is not audible, except in extreme cases. Yet, if it was not a problem, we would have not be seeing improvements to bias supplies in both headphones and loudspeakers operating on electrostatic principle.
 
It is icing on the cake, makes no real sense if "cake" is rotten; but when it is not ... 

 

[Nemeske88]

Thank you for the useful information. I checked the schematics on the internet and I've only seen some high voltage capacitors, no batteries. I presume these are the 'biasing voltage keepers' those must be kept 'charged' with the audio signal.

 

[davidsh]

  Thank you for the useful information. I checked the schematics on the internet and I've only seen some high voltage capacitors, no batteries. I presume these are the 'biasing voltage keepers' those must be kept 'charged' with the audio signal.

Yes, I think that's what you are referring to, charging up the bias voltage with the audio signal 

I don't know what it does to sound quality, I'd think it isn't significant, depends on implementation.