[davidsh]

The typical capacitance of the stator-stator is in the order of 100 pF by the way.

 

[chinsettawong]

Hi Dave,

I used to use Staticide ESD, but I ran out of it. If you've read through the thread, I'm sure you know that I now use a floor cleansing liquid to coat my diaphragm. It's readily available in big supermarkets in my area, and it's cheap.

I use contact adhesive for gluing the diaphragm. Other kinds of glue don't stick to Mylar that well. You can put a lot of tension on the Mylar and a good contact adhesive will hold it. No problem. I apply the glue to the spacer and let it dry for a couple of minutes. Then I press the spacer against the Mylar and they bond tightly right away.

Wachara C.

 

[inuponken]

Updated my clone.
 
Reduced tensioning for more bass but becomes unstable so I changed thickness of the spacers.
It lowered sensitivity but no problem with my KGSS (not HV) and DIY T2.
Very stable and bass is deeper than my SR-407.

 
Diaphragm = 2u Mylar film (e-bay)
Dust filter (front only) = 0.9u Super ultrafilm (http://www.indoorspecialties.com/)
Frames (cups): 3/4” Red oak board + wood stain + Gross Polyurethane paint (Home depot)
Stators: t=0.94mm FR4 PCB (e-bay PCB depot) + “KRYLON Digital Photo & Paper Protectant” splay for the coating (office).
Dust filters: t=0.94mm FR4 PCB (e-bay PCB depot)
Spacer & Diaphragm: t=0.5mm FR4 PCB (e-bay PCB depot) > t=0.8mm FR4 PCB
Contact Cement: DAP Weldwood original contact cement (ACE hardware)
Plastic Rings for the ear pad: Cut out from Compact Disc
 
Locking Rings for ear pad: from HE-5 Ear pads (e-bay)
Top plates: 3/16” black acrylic sheet (e-bay)
Nylon screws, small wood screws, shrink tubes…
Punching metal plates: Kenwood Excelon Speaker Grills (e-bay)
Cable: KOSS ESP950 extension cable (Koss service center)
Stax connector: from Kevin
Headband : form my SR-40 (Garage sale) + coat hanger
 
Tension = 180g (water bottle 120g + Clamp 60g) x 16pcs = Total 2,880g > 11.8g (Clamp only) x 30pcs =Total 354g (stopped at wrinkles are gone)
2 gallons bucket for tensioning (ACE hardware)
2in.Spring Clamps for tensioning x 16pcs (Harbor Freight/Home depot) >  HDX 3/4in Mini Spring Clamp x 30pcs (Home depot)
Ozakra 16.9-floz empty bottles x 16pcs (from recycle bin in my garage)
Vinyl coated wire rope = water bottle <> Clamp (from my wife)
And dxf files from Wachara. 
 

I am asking my wife to make ear pads for JF clone but I don’t know when she can finish…

 

 

[chinsettawong]

The drivers look really nice. Congratulations!

How will you make the headband?

 

[inuponken]

Thank you.
 
I'm still thinking how to attach the 1/8" steel rod to the back panel because I have several ways to attach.
 

 

[chinsettawong]

That looks interesting.  Let me know how well that works. 

 

[ayaflo]

Hello all,

I am doing for a second time a simple circuit for the esl cans I am making...I am stuck with the step up trafo for the audio signal and though torroids make all the difference from an EI core, torroids are unavailable for a few weeks here. I also tried the PA line trafo and apparently I need to wind my own and it costs $30 to wind to specification.

What are the alternates ? The closest I got here is a 240 to 27v step down that gives 10 amp current so it should be rated for at least 270W. Once i reverse this will this trafo be able to handle a 40 watt 4 ohm imp. Rated amp and in turn be able to step up the voltage for the stators?

PS- The last ESL speaker I made worked a few seconds till the trafo gave way so I can't take the chance now.I did check out the thread again but doubts remain.

 

[chinsettawong]

Hi Ayaflo,
 
Are you making headphones or loudspeakers?
 
Either case, you need a lot higher turn ratio than 240 to 27V can do.  For headphones, the turn ratio IMO should be at least around 1:40.  For loudspeakers, I would go higher than 1:80.
 
Try finding a pair of 240V to 6V transformers to use with headphones.  That will give you a step up ratio of 1:40.  If you can't find them, you can use a pair of 240V to 12V for a similar result by simply series the 240V windings and parallel the 12V windings.
 
Good luck.
 
Wachara C.

 

[ayaflo]

  Hi Ayaflo,
 
Are you making headphones or loudspeakers?
 
Either case, you need a lot higher turn ratio than 240 to 27V can do.  For headphones, the turn ratio IMO should be at least around 1:40.  For loudspeakers, I would go higher than 1:80.
 
Try finding a pair of 240V to 6V transformers to use with headphones.  That will give you a step up ratio of 1:40.  If you can't find them, you can use a pair of 240V to 12V for a similar result by simply series the 240V windings and parallel the 12V windings.
 
Good luck.
 
Wachara C.

 
The last time I reversed a 240 to 6V trafo, it either shorted in the 6 V side due to the 20-23V (65W) that my A/V reciver was feeding it or the 240V side due to the huge step-up and poor isolation that couldn't handle the step up.
I think for a 6V trafo, the secondary should at least have a 5-10 Amp current rating (so the trafo rating would be close to 30-60 VA/W) to accept such loads as my 65 wpc amplifier.
 
Anyway worth sharing I thought is  a very convenient method, I am using perf-boards for the stators. These perf-boards have all their points connected across columns, therefore soldering across one row will give me a stator board without any extra material for unwanted capacitance. 
 
Thanks for the wish, I need it.

 

[davidsh]

The problem should not be the current rating, I'd think, but rather that the trafo you used isn't designed to swing 23/900 volts. The current used by the transformer ought to be very low, ideally, as the ES headphone doesn't require much current.
It'd probably be best if you could find a low current, high voltage rated trafo.
 
Someone correct me if I'm wrong.

 

[ayaflo]

If you look for a low current high voltage trafo then you are not getting the step up needed. I know the current should be low and voltage high for the stator peak to peak voltage to work against the bias. however the transformers load rating is important since I am practically feeding my amp into it as an elemental design and what the trafo can take should be noted else it can short. The only option is to use multiple transformers to carry the load and this will work.some torroids also work since 25 watt torroids are way too common now.

 

[chinsettawong]

Your problem could have been your coating on the diaphragm that isn't good enough or the bias voltage that isn't high enough.  If you have everything correct, I doubt you need so much power to feed your transformers that would burn them in the first place. 
 
How big is your active area?  How thick is your spacer and what is your bias voltage?

 

[ayaflo]

I used dish soap last time... This time I am using floor cleaner. I am sure it's not the coating because I examined it. I highly suspect an internal shorting since tranformers with poor insulation are very common, especially once you reverse it, it can't handle the step up.

This time my bias is 609v and the spacer thickness is 1 mm. I will report back with the active area a few hours from now.

Thanks and best regards,

 

[chinsettawong]

Dish soap is certainly not that good.  Please also know that not all floor cleaners work either. 
 
If you are going with 1 mm spacer, you can use a lot higher bias voltage.   I have tried 1.2KV in the past with no problem. 
 
Good luck.
 
Wachara C.

 

[quintile]

Hi all.
 
I am new here and must admit I am not (currently) working on DIY headphones. I am however, trying to repair
a pair of Micro Seiki MX-2 electrostatic headphones, and I believe the people on this list may be able to help me.
 
The MX-2 used a diaphragm of "photo etched" polyurethane which is not stable long term - the diaphragms of my
headphones have disintegrated into dust. The diaphragms are only 47mm in diameter, and the stator spacing is
about 0.4mm. The bias is generated by an oscillator from a 9v battery, and sadly this is died too so I don't know the
HT voltage - I believe it is in the 200-300V range.
 
I have a few questions if anyone can spare the time:
 
Approximately what tension should I be aiming for? some people seem to suggest as high as possible before
the Mylar rips. Some people suggest as low as possible which still removes all the wrinkles. what is the effect
on the frequency response?
 
What target resistivity should I aim for? 10e8 seems to be suggested, is this still current best practice?
 
How should I measure resistivity - has everyone bought a surface resistivity meter? I DVM only goes
up to 30M ohms.
 
I have read about the different dope that people coat their diaphragms with, but I don't understand why rubbed
graphite is not more popular - In my experiments (with lock lubricant, not colloidal aquadag) I found the resistivity
tends to drop rather too low, but this may be my lack of experience. It looks a good material, not being hygroscopic
and no problems with ageing.
 
Finally, the most difficult problem The MX-2 uses a small electrostatic capsule which is easily replaceable. This has
metal stators held in two interlocking molded plastic  rings. The diaphragm is glued to a metal ring which
is held between the plastic rings and contact is made from this ring.
 
The difficulty here is there is only a point contact to one side of the diaphragm, and the "contact" through the
conductivity of the glue.
 
Does anyone have any experience of conductive glues which would adhere well to Mylar and metal? If
no one has any better suggestions I am going to try uhu por and mix some graphite with it but this will
be hard as it dries rather quickly.
 
I have sourced some 1micron Mylar and also, as an alternative to rubbed graphite,  some EPA surface cleaner
http://www.teknis.co.uk/p-1114-epa-surface-cleaner.aspx
though I have no way to know if it is stable long term (many years).
 
Sorry for so many questions, Thanks for any help.
 
-Steve