[Congo5]

   
 
Nice work!  How do you like your Megatron?
 
Yes, using the inner tube stretcher, you can easily over stretch your diaphragm.  You have to be extremely patient and gentle when applying the air into the tire.  
 
Wachara C.

    The Megatron is well worth building,  Its different than the KGSSHV.  I do not use it  in the summer due to heat,
or when I just want to listen/test for a few minutes. It's hard to describe the sound but I like it very much. its very pleasing.
 
  And since you can wind the transformers.....  highly recommended!

 

[chinsettawong]

 
    The Megatron is well worth building,  Its different than the KGSSHV.  I do not use it  in the summer due to heat,
or when I just want to listen/test for a few minutes. It's hard to describe the sound but I like it very much. its very pleasing.
 
  And since you can wind the transformers.....  highly recommended!

 
Megatron is certainly on my "to do" list, but I think it'll be a while.  It's nice to know that you like it though.
 
I did try winding my own transformers before, but it's too much work for me.  Buying them is a lot easier.
 
Wachara C.

 

[NoPants]

The Megatron is nice, I recommend a 400V build based on the heat from running at 450

 

[Congo5]

   
Megatron is certainly on my "to do" list, but I think it'll be a while.  It's nice to know that you like it though.
 
I did try winding my own transformers before, but it's too much work for me.  Buying them is a lot easier.
 
Wachara C.

Yea I would not want to wind 7 6.3v filaments, 2 420v and a 16-0-16v. could it be done all in one?
 
  Tonight every thing seems to be working...


oh I started using the pps transistor washers from the KGSSHV so that I can use metal screws...
 
all these work,  wish I knew why 
 
Thanks

 

[Congo5]

  The Megatron is nice, I recommend a 400V build based on the heat from running at 450

yes that is what Spritzer said > so that is what mine is..
 
still wonder what more would be like.

 

[NoPants]

I'm running at 450 which is why I'm recommending the downgrade. Having built the 350V KGST, 500V KGSSHV, 450 Megatron, and comparing them to the BHSE (400V?) I can safely say it's not that big a difference.
 
If you want "more" maybe you can build the fancier power supply at 400V, compared to the Blue Hawaii PSU
 
Other ideas include
DC filament supply on the input supply, separate 300V supply
nicer coupling caps like Mundorf supremes, one guy put solens in his iirc
 
I would explore these before simply rasing the voltages, but that's just me

 

[chinsettawong]

 
Yea I would not want to wind 7 6.3v filaments, 2 420v and a 16-0-16v. could it be done all in one?
 
  Tonight every thing seems to be working...


oh I started using the pps transistor washers from the KGSSHV so that I can use metal screws...
 
all these work,  wish I knew why 
 
Thanks

 
Wow!  You are catching up really fast.  

 
How do you like the sound of each design?
 
Wachara C.

 

[Congo5]

   
Wow!  You are catching up really fast.  

 
How do you like the sound of each design?
 
Wachara C.

yup only 2yrs 3mo preparing 

 
well just holding them up to my ears they sound very similar. And all Good>>>>
 
when you account for diaphragm tension as some are tighter and  have less bass.
 
If I had to pick right now I would say the best is the lower middle black one with less open area / smaller holes.
 
to my surprise the design and hole size doesn't seem to make much difference. 
 
based on advice in this thread All are = or >80mm active area.
 
what does matter is the coating and Pads! lots to get right with Pads.
 
Thanks

 

[chinsettawong]

   
If I had to pick right now I would say the best is the lower middle black one with less open area / smaller holes.
 
 

 
 
Really?  I very much prefer the ones with bigger open area.  If you have good ear pads, you can tell very clearly that the ones with more holes (open area) have a bigger sound stage.  That's how I like my headphones, anyway.
 
Really nice work!
 
Wachara C.

 

[urlgr-A]

Hi ondesx
 
QUOTE
Originally posted by ondesx
 
"I don't see a robust method for coating the Mylar for ages at the correct resistivity !
 
Yet QUAD used a coating that was known to last more than 25 years !...
 
Any other advice welcome..."
 
 
How about trying polymer sealant? It is normally used instead of wax after washing your car. 
As it is designed to stick very well to paint finishes and is 'anti-static', it might also stick well to diaphragm materials.  It's waterproof, so I guess unaffected by humidity. Lasts for months in direct sunlight too. I suppose you just wipe it on and let it dry but that part might need some experiments. You are further ahead than me as I still haven't got my Mylar yet but that is what I am going to try first.
 
urlgr-A

 

[Congo5]

   
 
Really?  I very much prefer the ones with bigger open area.  If you have good ear pads, you can tell very clearly that the ones with more holes (open area) have a bigger sound stage.  That's how I like my headphones, anyway.
 
Really nice work!
 
Wachara C.

Well I could be completely wrong at this point,
more soundstage is what I was expecting, 
so not hearing that I chose the easy to source pad version.
also mental bias towards what stax has done?
 

  Hi ondesx
 
QUOTE
Originally posted by ondesx
 
"I don't see a robust method for coating the Mylar for ages at the correct resistivity !
 
Yet QUAD used a coating that was known to last more than 25 years !...
 
Any other advice welcome..."
 
 
How about trying polymer sealant? It is normally used instead of wax after washing your car. 
As it is designed to stick very well to paint finishes and is 'anti-static', it might also stick well to diaphragm materials.  It's waterproof, so I guess unaffected by humidity. Lasts for months in direct sunlight too. I suppose you just wipe it on and let it dry but that part might need some experiments. You are further ahead than me as I still haven't got my Mylar yet but that is what I am going to try first.
 
urlgr-A

I can not find the exact products Wachara uses and am going to try some of what is here.
Also want to try some of the car products.
RainX and one of my TireBlack gels says polymer, vinyl protectant, ect.
 
if plain floor cleaner works ,,,,,  so does other things.
 
Also its a good Idea to make your design easy to change the film for coatings and cleanings.

 

[ondesx]

Hi All,
 
After extensive "bibliography" on this topic, I went to the conclusion that NONE product seems to do the trick !... Some for their too low surface resistance (SR), some others because they don't last enough, most of them because the "homogeneity" of the coating is far from perfect !... 
 
All these issues have the same consequence : the increase of distortion immediately or with the time !
 
Then I have a short question : why not use an aluminized Mylar ? There are several. They are "perfectly" coated and homogeneous. Since their SR is much lower than the clear Mylar coated with various experimental solutions (10^9-10^11 ohms/square), perhaps a much lower polarization resistance will do the job ? 
 
If I correctly understood, the issue with aluminized films, most often, is the firing of the diaphragm if the stators are insufficiently insulated, but it seems this insulation is more easier to perform with small surfaces of headphones, isn't ?
 
Thanks for any feedback.
 
OndesX

 

[urlgr-A]

Hi ondesx
Please tell me, what were your findings for polymer sealant? I ask because I have not found such information.
 
You talk of homogeneity of your coating. Whilst I understand it is desirable to have a lasting coating that is as uniform as possible, other people's efforts have produced outstanding results without recourse to attaining homogenous coatings. Please look at the restoration of Quad electrostatic speakers using a nylon based coating.
 
http://www.quadesl.org/index.php/hard-core/panel-coatings/original-quad-coating
 
This is done at home with a small piece of cloth dipped in the solution and spread onto the membrane, manually! After drying the coating is visibly non-uniform but is the equal of the coating it replaces and will last perhaps 20 years, or so it says. I realise this is for speakers yes but the principles are the same are they not? One can adjust the SR of the coating too.
 
Another point is that if using aluminised film, there are serious problems to be overcome:
 
 A quote from Sanders The Electrostatic Loudspeaker Design Cookbook in this university project thesis mentions exactly what you are considering:
 
https://courses.physics.illinois.edu/phys406/Student_Projects/Spring13/Nicholas_Jarosz_P406_Final_Project_Report_Sp13.pdf
 
So there are still plenty of things to actually try. btw Wachara's coatings are not giving up just yet as far as I know!  

 
 
Cheers!

 

[ondesx]

  Hi ondesx
Please tell me, what were your findings for polymer sealant? I ask because I have not found such information.
 

Hi urlgr-A,
 
After extensive study, I think that I'll give a try to conductive epoxy... It seems this is the best way to perform long lasting bonds between PCB and several other materials like PMMA and Mylar for example (i. e. for my personal needs...).
 
As far as the coating of the diaphragm, presently I only have several thicknesses of clear Mylar, then I'll give a try to an anti-static solution like the Reztore from ACL (I already have a sample). Since that are my first cells I have to go to one direction or another...
 
I thank you very much for the link of this thesis. I began the reading and I noticed several interesting answers to some of my questions. Particularly, about the thickness of the films for example... Interesting too, the point about the aluminized Mylar !
 
OndesX

 

[chinsettawong]

For your first pair, I would suggest that you stick with what I suggested.  You might not have known, but it took me a very long and frustrating time to actually find something that's cheap and works.  As for me, I have stopped trying to find other coating materials.  I like what I use and I'll stick to them.  I wasted too much time in the past without anybody giving me good guidances.  I just hope you guys listen to me and just make your headphones. 
 
If you want to do experiments, I propose that you try different driver designs, different diaphragm materials and thicknesses, different ways to stretch your diaphragm and etc. 
 
About glue, the best glue that I've tried is still rubber glue (contact cement).  Try and you'll see why.
 
By the way, aluminized Mylar is known to be a "no, no" for diaphragm.
 
Good luck.
 
Wachara C.