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My DIY electrostatic headphones - Page 105

post #1561 of 2618

Thanks arnoud

So Stax does its tensioning to get 120Hz to 150Hz. Pretty tomtom drum tight then. That's a useful nugget to note down.

When I was thinking about this, it was really from the point of view of what a drag it might be to disassemble each driver to perform tensioning.

Far better I thought to not give dust a chance to enter - not disturb anything and just turn a little screw or adjuster somewhere.

A lot easier said than done. 

Patience is what I need.

 

btw I am just down the road from you in Kyoto.

post #1562 of 2618

Thanks chinsettawong

Quote:
 

You can also do it my way.  I always cut more spacers than I need.  I glue a few more diaphragms to play with different tensions.

 

If you want to do the adjustable diaphragm, please do not forget that you're playing with lethally dangerous high voltage too.  Be very careful.

 

Yes the high voltage had not escaped my notice. As I am sitting here just theorising, for me, as a beginner in this I will probably do as you say

and just make a number of diaphragms at different tensions. Are you still using 3 micron mylar?

 

Another question for you. Long ago in this thread you found you could control the brightness of the sound by removing excess copper from the stators.

I am considering making stators from microwave oven doors (so they are all metal - no FR4). This means I am starting with a stator that is all holes and

no blank areas. The sound might be bright- I have no idea but, do you think it would be possible to adjust the high frequencies by covering a few of the stator

holes on the back of the stator with conductive copper tape? Obviously this adjustment would be made without any high voltages present :smile_phones:

 

With all this thinking about the headphones I have yet to consider what amp to build for it. I won't be able to test anything until I get that part done will I?

post #1563 of 2618
Quote:
Originally Posted by urlgr-A View Post

Thanks arnoud
So Stax does its tensioning to get 120Hz to 150Hz. Pretty tomtom drum tight then. That's a useful nugget to note down.
When I was thinking about this, it was really from the point of view of what a drag it might be to disassemble each driver to perform tensioning.
Far better I thought to not give dust a chance to enter - not disturb anything and just turn a little screw or adjuster somewhere.
A lot easier said than done. 
Patience is what I need.

btw I am just down the road from you in Kyoto.

No worries, should lookup measurements I made before to confirm.

We must meet some day, there are another couple of stat nuts in tokyo, we organize meets sometime.
We have one of chinsettawong diy with us at the moment, you could see how it works!
Still waiting for my bhse to drive them properly though as some of his units need a lot of juice...
Cheerrs,
Arnaud
post #1564 of 2618

How about adjusting the tension of the diaphragm via a mechanism similar to an adjustable drum head.

 

I can think of a way to proto' a threaded headphone shell using a large plastic jar lid with a large hole cut out of the centre so that when you tighten the lid down on the top of the jar ( also plastic ) it traps the diaphragm ( already stretched on the usual ring, like a drum head ) dragging the ring over the lip of the jar thereby adjusting the tension according to how tightly the lid is screwed down.

Most of the plastic jar could be cut away leaving just the threaded 'neck'.

I don't have any good ideas re' how the stators would be integrated, maybe just the usual arrangement of spacers,stators and diaphragm stacked up, but in this case between the jar lid, and the jar neck.

post #1565 of 2618

Hello n3rdling and thank you for your detailed reply.

Regarding the possibility of using microwave oven doors as stator material, well, I have already got my doors from a scrapyard! I checked the holes and spacings. All the holes are circular.There are two sizes among the five doors I managed to obtain.

1.2 mm holes, with 1.5 mm centres. 1.3 mm holes, with 2 mm centres. The pattern of hole centres in both cases is based on equilateral triangles and not a parallel grid. Imagine a honeycomb but with circular holes instead of hexagonal holes. ( I know there must be a proper name for this pattern). These measurements are just from visual checks from pictures I took. Actually I want to upload the pictures but I can't seem to do this. I don't have permission the message tells me...

 

You mentioned that the diaphragm is glued to the spacers. The idea I have doesn't have them glued to the spacers at all but if sealing at the spacer diaphragm boundary is needed them I was thinking of a thin bead of silicone sealant to do this. 

The mechanism is difficult to describe without pictures so I need to sort out how to do that. But as Q Mass succinctly put it, it works like the adjustment of the tension on a drum head.

 

I am also wondering about tailoring high frequency response (i.e. trying to fly before I can crawl :Dusing copper conducting tape to cover some of the holes on the backs of the stators. Chinsettawong describes removing copper where the holes are absent from his pcb stators and it affecting the response so I surmised that I might be achieving a similar effect by doing it this way (isn't what I am proposing a feature of the SR-007 mk2 stators? ) . What do you think?

post #1566 of 2618

Hi Q Mass and thanks for your comments. 

The mechanism you describe is indeed something like what I have in mind. I want to upload some diagrams but I don't have permission. Probably because I am a newbie here... I guess. I need to take a proper look at the forum rules.

post #1567 of 2618

Hello arnoud....

 

Sorry I didn't get back to you sooner.   Do you still have one of chinsettawong's headphones with you now?  Oh wow. I would really love to see them!  Which ones are they? 

As far as meeting up sometime, yes I would love to do that.  You say you are waiting for a BHSE, so that means you are waiting for a chunk of cash to woft your way, or have you really bought one? (Sorry, I am relatively poor, so all this talk of Blue Hawaii and SR-009 vs SR-007 is way beyond my means at present.)

 

I have a few of questions. First about the Stax SR-009. (I am looking around on this thread and in other places but not a satisfactory answer found as yet)

 

What is the purpose of the large hole in the centre of the stator? It is somewhat trumpet shaped/tapered in profile yes?

 

What is the extent of the conductive coating pattern on the diaphragm? What I mean by this is, is the center uncoated (and therefore undriven I suppose). I read that some unidentified Stax engineer said it was to do with temperature. Hmm.... do they ever get that warm? Is it a way to contour the frequency response somehow?

 

I can now upload images so attached is my proposed stator material. There are two sizes as you can see. What do you think? I am thinking about ratios of open hole area here as well as hole sizes.

 

 

Do you think either size is suitable? The material appears to be painted steel. The entire door is pressed and finished off in one piece i.e. the mesh is integral to the door.

 

Another question, would the eXStatA be a good amp to drive my home grown stats? Or is there anything else you can recommend? I am currently on the verge of ordering components you see. 

 

Regards.

post #1568 of 2618
Thread Starter 

Hi urlgr-A,

 

Your perforated metal sheet looks good.  I'm sure either one will work just fine.  Please be sure that the metal sheet still has very good insulation.

 

What would you use for your spacers?

 

The headphones with Arnaud now are my version 1, Jacklin Float style headphones.  The spacer is 0.6 mm, and yes, they require a bit more powerful amp than Stax headphones.

 

If you want to build your own amp, I highly recommend you build a KGSSHV.  It's relatively easy to build.  I also have an eXStatA, but I prefer KGSSHV.

 

Wachara C.

post #1569 of 2618

If you're on a tight budget try to look around for a used vintage SRM-1 Pro or SRD-7 transformer box.

post #1570 of 2618

Thanks Chinsettawong.

What would I use for spacers?

Well, I have some 0.5 mm styrene sheet (from Tamiya) as used by plastic modellers. I also have some 0.3 mm as well, so I can double it up to make 0.6 mm if need be. This plastic sheet is very smooth and of uniform thickness but not as stiff as very thin FR4 I guess.

If it is going to be clamped in a "stator sandwich" the will lack of stiffness matter?

 

Another possibilty for spacer material is Formica, a thermoset plastic laminate. 

 

I am thinking about using 2 or 3 micron mylar for the diaphragm material and contact glue to attach it to the spacers. Here in Japan there is one you can find in just about any DIY store called G17, a contact glue very similar to Dunlop Thixofix. I will stretch the mylar as per your method with 800g pet bottles.

 

Another knowledgeable Head-fier in this thread mentioned something about stabilizing the mylar once it is stretched. Do you advise doing this? If so, how do you do it?


Edited by urlgr-A - 10/6/14 at 5:26am
post #1571 of 2618
Thread Starter 
The stiffness from styrene foam by itself won't be able to hold the diaphragm tension. You'll need to glue it to the stator then glue the diaphragm on. But I'm not sure how stiff your stator is. The stiffness does matter, because the air gap is only 0.5 mm. Any warping can cause unevenness and your driver won't be stable.

I'm not sure how you can stabilize the diaphragm. Do you mean to use heat to further shrink the diaphragm? In my experience, if you use weight or inner tire tension method to tension your diaphragm, further heat shrinking doesn't help much at all.

Either 2 or 3 microns diaphragm sounds very good.

Wachara C.
Edited by chinsettawong - 10/7/14 at 7:25pm
post #1572 of 2618
Quote:
Originally Posted by chinsettawong View Post

The stuffness from stylene foam by itself won't be able to hold the diaphragm tension. You'll need to glue it to the stator then glue the diaphragm on. But I'm not sure how stiff your stator is. The stiffness does matter, because the air gap is only 0.5 mm. Any warpping can cause unevenness and your driver won't be stable.

I'm not sure how you can stabilize the diaphragm. Do you mean to use heat to further shrink the diaphragm? In my experience, if you use weight or inner tire tension method to tension your diaphragm, further heat shrinking doesn't help much at all.

Either 2 or 3 microns diaphragm sounds very good.

Wachara C.


The styrene sheet is not expanded foam like packaging material, it is actually a hard plastic sheet, not quite as stiff as FR4. As for the stator stiffness, I understand what you mean. I will see when I cut them out :blink: and therein could be a problem, so I was thinking that if they are not stiff enough, though I expect them to be good enough, then I will put a stiffening frame on the back of them similar to that used on the SR-009.  (Obviously I might lose some stator holes when doing this.)

post #1573 of 2618
Quote:
Originally Posted by urlgr-A View Post
 


The styrene sheet is not expanded foam like packaging material, it is actually a hard plastic sheet, not quite as stiff as FR4. As for the stator stiffness, I understand what you mean. I will see when I cut them out :blink: and therein could be a problem, so I was thinking that if they are not stiff enough, though I expect them to be good enough, then I will put a stiffening frame on the back of them similar to that used on the SR-009.  (Obviously I might lose some stator holes when doing this.)

 

I used 0.5mm styrene sheet to hold diaphragms in my early days of electrostatic headphones, it is not strong enough. Perhaps if you were to use a really thick rim it could, I was using about 7mm as the widest. It works alright if you never disassemble anything (the pressure of the driver screwed tight keeps everything in place). But if you then open it up in a week, the diaphragm will lose all its tension because the styrene no longer has the same strength and shape it did before.

 

It works great for all the other spacers you need though! Works great to hold dust covers where tension doesn't need to be so high. It's cheap and easy to cut compared to FR4.

post #1574 of 2618

n3rdling

I have taken your advice. Thank you.

I have found a used SRM-1 pro Mk2 PP version C.

This was the last of this model maybe... Perhaps you can correct me here.

 

 

Now for a question. Would it be fairly straightforward to make the bias voltage adjustable?

What would be a good way to achieve this? A separate box perhaps, a separate supply I mean.

I say this because it seems to be something that accomplished DIYers in this thread are doing when testing their creations.

post #1575 of 2618
Quote:
Originally Posted by urlgr-A View Post

 

 

Now for a question. Would it be fairly straightforward to make the bias voltage adjustable?

What would be a good way to achieve this? A separate box perhaps, a separate supply I mean.

I say this because it seems to be something that accomplished DIYers in this thread are doing when testing their creations.

 

It is for all practical methods impossible to make the output of an amplifier become adjustable bias by adding an external box. This is because the output impedance is very high, so you cannot simply add an adjustment potentiometer.

 

It is easy to make your own adjustable bias supply, though. Take whatever voltage supply you want, and put a very high value potentiometer across it. Then the output voltage is simply the wiper. Make sure to add ANOTHER very high value fixed resistor to this brush before going to the output. Otherwise at full voltage, you could get killed by the bias because the wiper would connect straight to the high voltage supply. Be cautious of safety, pots aren't really rated for bias voltage levels. Make sure the chassis is well grounded, and watch for arcs on first power up. I picked a random pot off the shelf, I think 10Mohm, and it worked with no problems.

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