My DIY electrostatic headphones
Mar 28, 2015 at 7:13 AM Post #1,801 of 4,064
Been lurking at this thread from the beginning almost. :)
 
Want to thank Chinsetta and Tachikoma, and others contributing to this thread.
 
Have a pair of 404's that in one side didn't sing much.
The driver has been re-coated. And now sings again :)
As Tachikoma has recommended quite a few times I wasn't shy applying the  coating. Used a micro fiber cloth to rub/polish the mylar as I didn't have a proper sponge.
 
No squeling, buzzing and I could play rather loud until the 212 sort of gave in.
I use some tape with mild adhesive to cleanup the stators before assembling. Seems to work fine.
 
I will glue the driver today and the it takes about 24 hours to harden up.
So I guess I'll have the final result in a few days.
 
The most tricky part of this seems to be cracking the driver open without messing up. I use a rather big Stanley knif with fresh blade, and a lot of patients ... but it does take a while to crack it open as for my experience.
 
Thanks again for all the contribution
 
Mar 28, 2015 at 10:32 AM Post #1,802 of 4,064
For those who are still interested in measurements and quantification, here is a simulation made with the simulator developed by Arend-Jan on his web site :
 
http://quadesl.nl/sim/
 

 
Don't worry about the yellow line : it is not meaningful.
 
You can see that for 500V of polarization and 750 V peak to peak of the modulation, the levels reached for the whole audio band are quite impressive, around 108 dB !...
 
OndesX
 
Mar 28, 2015 at 1:14 PM Post #1,803 of 4,064
  I use a rather big Stanley knif with fresh blade, and a lot of patients ...

Hannibal, is that you?
wink.gif

 
Mar 28, 2015 at 2:07 PM Post #1,805 of 4,064
  For those who are still interested in measurements and quantification, here is a simulation made with the simulator developed by Arend-Jan on his web site :
 
http://quadesl.nl/sim/
 

 
Don't worry about the yellow line : it is not meaningful.
 
You can see that for 500V of polarization and 750 V peak to peak of the modulation, the levels reached for the whole audio band are quite impressive, around 108 dB !...
 
OndesX

 
http://quadesl.nl/sim/ said:
Like any simulator you can make it do thinks that can not be done in real life.
... I guess this simulation doesn't really apply for nearfield, actually you need to be far field for the Walker-equation to be valid AFAIK.
 
Anyways, I really appreciate your postings/efforts in trying to make the stretching process repeatable. Thanks for the effort/contribution.
 
Mar 28, 2015 at 3:08 PM Post #1,806 of 4,064
Originally Posted by soren_brix /img/forum/go_quote.gif
 
 I guess this simulation doesn't really apply for nearfield, actually you need to be far field for the Walker-equation to be valid AFAIK.
 
Anyways, I really appreciate your postings/efforts in trying to make the stretching process repeatable. Thanks for the effort/contribution.

 
You're probably right, but anyway I guess it'll give an idea of how it'll work and delivers some numbers !
 
Thank you for your kind words.
 
OndesX
 
Mar 29, 2015 at 12:35 AM Post #1,807 of 4,064
I had posted numerical simulations in this thread I believe, trying to explain what dude500 observed with various pads depth / size.

Conclusion for me was that you have to think of it as a system. For instance, the free air resonance of driver has nothing to do with the coupled resonance once it is acoustically loaded by the eadpad cavity.

As such, ear pad depth, the amount of leakage through the pads and/or pad-baffle gap all matter. That's why I referred to stax phones earlier in case your design ressembles their dimensions: for omega series, a free air resonance in 120-150hz range translates into a coupled resonance in 40-60hz region which sounds about right target.
 
Mar 29, 2015 at 9:07 AM Post #1,809 of 4,064
  Been lurking at this thread from the beginning almost. :)
 
Want to thank Chinsetta and Tachikoma, and others contributing to this thread.
 
Have a pair of 404's that in one side didn't sing much.
The driver has been re-coated. And now sings again :)
As Tachikoma has recommended quite a few times I wasn't shy applying the  coating. Used a micro fiber cloth to rub/polish the mylar as I didn't have a proper sponge.
 
No squeling, buzzing and I could play rather loud until the 212 sort of gave in.
I use some tape with mild adhesive to cleanup the stators before assembling. Seems to work fine.
 
I will glue the driver today and the it takes about 24 hours to harden up.
So I guess I'll have the final result in a few days.
 
The most tricky part of this seems to be cracking the driver open without messing up. I use a rather big Stanley knif with fresh blade, and a lot of patients ... but it does take a while to crack it open as for my experience.
 
Thanks again for all the contribution

The glueing went a bit wrong.
The stators ended up being a tiny bit misaligned - not much, but enough for the eye to witness the displacement when holding up the driver and looking through the driver. When the stators are correctly aligned it is rather hard to tell if there are one or two stators, even if looking at an angle.
The displacement resultet in an imbalance.
Dismantled the driver again. Cleaned all glue off the drivers and asssembeled the driver, now being hold together by some strong tape.
The two drivers apparantly have about the same volume again.

Still no squeling/buzzing or other strange noises :)
I guess I need a simple jig to keep the stators in place while glueing.
 
Mar 30, 2015 at 10:36 AM Post #1,812 of 4,064
  Hmm.  A little misalignment shouldn't affect the sound level, IMO.  
 
Perhaps you should use a clamp or two to hold to whole thing together tightly when you glue it.

 
  Or two wood squares with a serious weight on the upper one, the whole thing on a plane surface, this will do the job perfectly !...

 
Actually did clamp it between two pieces of MDF covered with melamin ... but for some reason it ended up a bit misaligned.
Having the stators eyeball aligned the driver is as loud as the other one again ;o)
But thnx anyways ;o)
 
Apr 14, 2015 at 3:48 PM Post #1,813 of 4,064
A little update. We did finish our esl panel (physics project). Tried making our own transformer etc. It did play, though not very loud. Just tried connecting the panel to my srm-T1. It does play music very quietly. I'm at 12-2 o'clock and even then it is not loud at all. The sound is distorted as well, especially playing bass I think. It seems it is because parts or even most of the diaphragm has collapsed on one stator. Either the food film is bad or the tension wasn't high enough. Or both. That is my hypothesis at least.
 
Apr 14, 2015 at 11:00 PM Post #1,814 of 4,064
  A little update. We did finish our esl panel (physics project). Tried making our own transformer etc. It did play, though not very loud. Just tried connecting the panel to my srm-T1. It does play music very quietly. I'm at 12-2 o'clock and even then it is not loud at all. The sound is distorted as well, especially playing bass I think. It seems it is because parts or even most of the diaphragm has collapsed on one stator. Either the food film is bad or the tension wasn't high enough. Or both. That is my hypothesis at least.

 
Food film generally doesn't work well, it's too stretchy and permanently deforms before it has sufficient tension for use in an electrostatic driver. So yes, I would say you didn't have enough tension and probably couldn't get enough tension with the material you used.
 
Apr 21, 2015 at 1:39 AM Post #1,815 of 4,064
Why can the diaphragm collapse semi-permanently onto one of the stators, which forces enables it to do so?
 

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