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My DIY electrostatic headphones - Page 44

post #646 of 928
11/9/12 at 9:16am

Any issues with drivers that big?  They do look awesome!!  redface.gif

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post #647 of 928
11/9/12 at 6:03pm
Thread Starter 

Thanks, Birgir. 

 

The size of the drivers is very similar to that of Stax SR007.  The actual active diaphragm diameter of SR007 is 78 mm while mine is 80 mm.  With the diaphragm width this much, the tension on the diaphragm has to be very high to keep it stable.   

 

The only other issue I have while making this conversion is that the cups are coated with conductive paint underneath the black paint.  I only find out this after I've cut all the parts.  Therefore, I have to be extremely careful.  I etch out all the copper that could possibly come into contact with the cups, and I tape the outer perimeter of the drivers as an extra precaution.

 

The sound is similar to my previous Omega clone.  However, the comfort is a big issue to me.  They just aren't that comfortable to wear.  The earpads are rather bad too.

 

Wachara C. 

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post #648 of 928
11/10/12 at 12:34am

Having held my fair share of SR-Omega diaphragms... yup you need plenty of tension.  I'm sure the brass mounting rings would bend before that diaphragm.  smily_headphones1.gif

 

Pretty much all black paint is somewhat conductive due to the carbon die in it, something people rebuilding Quad ESL's have learned the hard way. 

 

Are those the HE-6 earpads?  They are really nasty indeed. 

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post #649 of 928
11/10/12 at 5:03am
Thread Starter 
Yes, they are HE-6 earpads. Nasty is the right word indeed.

The first layer of paint looks very much like chromium. The resistance is very low. I guess they want the black color surface to look shinny, and with the chromium underneath, it helps.

Wachara C.
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post #650 of 928
11/21/12 at 8:58pm

I've been doing lots of tweaks to get the sound more how I'd like it to be. Been continually increasing tension, and also decreasing the active area (tried 78mm like Stax uses and I like it much better than the 90mm I'd been using in the past). 

 

But I've been running into a problem. I've pretty much never made a diaphragm that after a couple days, didn't have a high pitched squeal develop. It is an inconsistant and fairly quiet squeal that comes and goes. It is not in the amplifier, because unplugging the headphones keeps the squeal going for quite some time from the stored charge. I have quite uniform and high tension, with no wrinkles even along the glue edge. Has anyone run into this issue? It always develops slowly after several days or weeks after assembly. When I take the diaphragm out and check the tension, it's the same as day 1, and nothing visually changed. The only thing I can think of is maybe dust getting in since I don't have a protection screen on the outer face. My coating material is anti-static cleaner.

 

Turning bias down to about 250-300v always clears it up indefinitely (at least to time lengths that I've tested, I have no way of knowing if it'd come up months later), but I would like to run at higher bias to keep efficiency up.

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post #651 of 928
11/22/12 at 8:12am

That would be dust causing those issues. 

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post #652 of 928
11/22/12 at 8:21am
Thread Starter 
Hi Dude_500,

Have you given up on your elvamide already? biggrin.gif

The squeal has nothing to do with the diaphragm tension. The sound that you hear is from the electrical discharging. In my experience, it can only happen when you either have some dusts inside the driver, or there is a small hole on your dust cover.

Yes, it can really be a pain to look for the dusts inside the driver. The dust can be so small that it can't be seen with naked eyes. I normally use a big magnifying glass to help me look for it. A simple and effective way to clean your stator is to use a piece of sticky tape to stick the whole surface of the stators. When you pull the tape up, the dusts come up together with the sticky side of the tape. I do that a few times just to make sure all the dusts have been removed.

Another way is to spray paint your stator with some plastic paint. Since the stators surface is now non conductive, the dust won't make the squeal.

Water condensation inside the driver is another major cause of the squeal. If your headphones start up with no squeal, but the squeal only comes after you've been listening for a while, then I think this is the problem. It takes only just a small pin hole to cause it. When you're listening, the humidity inside the cup can be quite high. The humidity eventually finds its way inside the driver and condenses into water. So, do not overlook a small pin hole on the dust cover.

By the way, may I ask you to tell us why you decide to use anti static cleaner? Is Elvamide not performing well?

With your active diaphragm diameter of 90 mm, it's extremely difficult to keep the diaphragm stable, right? If I were you, I would increase the spacer thickness a little more - say 0.6 mm. 0.1 mm sure makes a lot of difference.

Wachara C.
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post #653 of 928
11/22/12 at 8:42am

sorry, I have no experience with DIYing electrostatic, love to try one day though, but from my experience with diy thunderpants, you should try out the LCD-2 pads, i strongly believe that the quality of the bass from the Audeze has 80% to do with the pads ( of course to benefit, the driver should have fast bass, which i think electrostats have plenty) It need a few teak as the mids might become too thick, but worth trying

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post #654 of 928
11/22/12 at 1:00pm

I do have my stators painted with a relatively thick coat of spray primer. I have read that many spray paints are actually quite conductive though, I should check if the stuff I used is as that may be one reason it doesn't help much with the squealing. I do also notice the squeal coming up after long listening, and often it will come on quite badly after showering and still having wet hair. I have what I would consider to be a perfectly sealed sweat shield over the inside stator, but nothing on the outside stator. What do you use to keep dust (and possibly moisture) out of the outside? I recall at one point putting a mylar screen on both sides was discussed, but I think it was determined that caused a bit of bass rolloff (and as far as I know even most retail headphones don't have a film on the outside). 

 

90mm was indeed very difficult to get stable, 78mm is a huge difference in stability. I had it stable for about 350V bias, but never bothered get the tension high enough to get it stable higher. 

 

And yes, you're right... anti-static cleaner is great. I still would argue that if what you're after is ultra low tension then elvamide is the way to go (which is what I was going for early on, but at this point I like the sound of higher tension more anyways, and it's much easier to work with). The elvamide holds a much weaker charge so it's vastly more stable, of course it also is less efficient being that it has less charge, so it's all a balancing act where you have to pick your priorities.

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post #655 of 928
11/22/12 at 8:38pm
Thread Starter 

We can argue all day long about the coating materials.  As for me, if I want to use lower tension on the diaphragm, I would still use the same coating material, but I would lower just the bias voltage.  That's how I would do it.

 

What bias voltage are you using now with your 78 mm diaphragm?  Stack uses 580V.  I use 580-650V.

 

About the squeal problem, it's either dust or humidity that is causing it.  Be very patient.  Use a big magnifying glass, if you have to.

 

Good luck.

 

Wachara C.

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post #656 of 928
11/22/12 at 9:16pm
Quote:
Originally Posted by chinsettawong View Post

We can argue all day long about the coating materials.  As for me, if I want to use lower tension on the diaphragm, I would still use the same coating material, but I would lower just the bias voltage.  That's how I would do it.

 

What bias voltage are you using now with your 78 mm diaphragm?  Stack uses 580V.  I use 580-650V.

 

About the squeal problem, it's either dust or humidity that is causing it.  Be very patient.  Use a big magnifying glass, if you have to.

 

Good luck.

 

Wachara C.

 

Right now I'm sitting at about 250V to keep the squeal down until I fix that, I've gone up to 400V on the 78mm stators, and can switch a wire in my supply to get adjustment up to 700V when I fix the squeal.

 

I could go through the work of cleaning the dust out, but I don't see the point... won't it just fill up again? There are stator holes exposed to the atmosphere on the outside face.

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post #657 of 928
11/22/12 at 10:03pm
Thread Starter 
Quote:
Originally Posted by dude_500 View Post

 

Right now I'm sitting at about 250V to keep the squeal down until I fix that, I've gone up to 400V on the 78mm stators, and can switch a wire in my supply to get adjustment up to 700V when I fix the squeal.

 

I could go through the work of cleaning the dust out, but I don't see the point... won't it just fill up again? There are stator holes exposed to the atmosphere on the outside face.

Hi Dude_500,

 

If you don't listen, nobody can help you.  I've made many electrostatic headphones, and I know what am doing.

 

If you're so worried about the dust, you can certainly put another dust cover on the backside.  

 

Wachara C.

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post #658 of 928
11/23/12 at 9:25am
Quote:
Originally Posted by chinsettawong View Post

Hi Dude_500,

 

If you don't listen, nobody can help you.  I've made many electrostatic headphones, and I know what am doing.

 

If you're so worried about the dust, you can certainly put another dust cover on the backside.  

 

Wachara C.

Not sure what I'm not listening to... I fully accept that it is dust and am glad to learn that is definitely the issue. My question was what people are using for dust covers. I may have missed it, but unless I'm mistaken nobody has discussed what they now use with the exception of a second mylar film, which was determined many months ago to quite likely inhibit bass response.I have used felt, but that changes the sound signature quite a bit.

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post #659 of 928
11/23/12 at 6:59pm
Thread Starter 

For what I know, you are making your headphones exactly the way I make mine.  I only use the dust cover to cover the inner side of the driver.  I leave the other side completely open to the atmosphere.  I've been doing that for many years.  The reason for me is that when I cover the outer side with another Mylar dust cover, I tend to get less bass, and I don't like it. 

 

If you want to, you can cover the outer side with very fine screen mesh cloth.  I think that's what Sennheiser did on their HE-60.  Here are some pictures of the HE-60 driver.

 

This first photo shows the dust cover that is facing your ear.

 

 

This second photo is the other side of the same driver.

 

 

 

Wachara C.

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post #660 of 928
11/24/12 at 1:05am

If you are loosing bass due to the back dust cover then it's simply too tight and bounces back some of the low frequencies causing them to cancel out. 

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