Q: DuPont Mylar Film for ESLs...

[Audiofanatic]

Hi Gaz,

You can do that without any problem.
But! Be shure to use the best tape you can buy!
I use the best glue there is, from BISON.

Are you going to make it with pvc isolated wire or with perforated metal?

I wish you luck with your plans.

Regards,

Audiofanatic

 

[Rarkov]

Hi,
Before I go on, it'd be rude not to let you know how beautiful your ESLs are!!! Fantastic work. (Or are they what you made clones of?) Either way - excellent!

I have got the Mylar. I ordered it from One Thing Audio. I believe it is used for repairing Quad ESLs (66? Something anyway!). Unfortunatly it is about 23microns thick which is more than I wanted, but hopefully I should get quite a bit of tension.
I am sourcing some 1.5mm or 2mm acrylic for the spacers (about 1.7mm seems to be optimal but hopefull 1.5 bulked out with tape will do it). Finally, the stators are the only thing I haven't sourced. I am getting quotes on 1.5mm mild steel perforated plates with 50% coverage of 3mm holes. I will get them powder coated (only £25 for all 4!). One company quoted £80 for the mild steel!!!

Does this sound OK? Will it make much difference if a D/S spacing is 2.1mm instead of 1.7mm? Does that sound right by the way. Sounds like an awfully small gap to me!

Thanks,
Gaz

 

[Audiofanatic]

Hi Gaz,

The ESL's are the original ones, I'v made a clone of those.
The Mylar is to thick, you'll see when you'r ready to listen to your ESL's.
I can send you 4 or 6 micron if you want via a friend of mine, 80cm resp. 100cm wide.

The gap is o.k! the bigger the gap, the lower the db!


I'm going to bed now.

I'll continue tomorow

Audiofanatic.

 

[peterr]

Unfortunatly it is about 23microns thick which is more than I wanted

This really is very thick. I can't imagine Quad uses this.

I use the 6 micron variety Audiofanatic speaks about and it is very good. It is also in the link in my first post (the stuff from MartinJan Dijkstra).

I too used tape to glue the mylar to the spacers but I have used glue (bisonkit it is called in holland) to fix the spacers to the frame.

My D/S spacing is 2mm. I would rather go to 2.5mm then to 1.5mm if you intend on using your ESL at or close to full range.

Make sure to have your metal powdercoated at least twice maybe even three times to create a thick enough insulation layer.
Also I read somewhere (did not test it myself) not to use black paint as it contains carbon particles (to make it black). This gives it a much lower resistance at these high voltages.

Good luck

 

[ashok]

Be extra careful.

I am also working on an electrostat. I just wanted to caution all those new to DIY and especially working with ESL's, be VERY CAREFUL about the voltages. Use rubber gloves when working with powered units. These devices can shock you VERY badly if not KILL you if you touch live parts. Remember that the ESL is a capacitor and so can store a charge at very high voltages. While these are highly resistive , the power transformer/power supply and step up transformer are especially lethal. With kilovolts around you can even blow a normal DMM !!
BE CAREFUL.
Cheers.

 

[Rarkov]

Don't worry. I'm exceedingly wary of Power Supplies. I had no prior knowledge of high power PSUs when I built my monoblocks with 500VA PSUs, but I did it, and I'm happy with them, but I certainly do not go poking around in them...or if I have had to quickly discharge large caps, it's been on the end of a long screwdriver!

I will be even more wary of kV sized PSUs! Out of interest, if using a DMM with a step down resistor network, how far can I expect the PSU to spark to the probes (or me) when I go to measure them. Will there be a spark at all?

BTW: How much would people expect to pay for perforated sheet mild steel with the following specs:

2mm thickness (2000mmx1000mm)
50% hole coverage.
3mm hole at 4mm pitch
£72.76 per sheet (need 2!)


Thanks,
Gaz

 

[wrl]

Does anyone know where to purchase the audio step up transformers?? I tried the electrostatic loudspeaker exchange, but they seem not to be answering their e-mails and their phone line is disconected. HMMM methinks a bad sign.

Anyway, if anyone knows where I could get these it would be appreciated.


Thanks,
Wes

 

[ashok]

Winding your own.

I think this is probably a bit like winding audio transformers for a tube amp. Only hitch is that it uses higher voltages on the secondary and so insulation schemes will be more important.

Has anyone started winding an audio output transformer yet ?
If you have never wound a transformer - it might be much better to buy one.
Cheers.

 

[ashok]

Check this ...............

http://www.justrealmusic.com/content/transformers.htm

and
http://www.amplimo.nl/en-us/dept_30.html

and

http://www.sowter.co.uk/esl.htm

and this
http://www.audiocircuit.com/9041-esl-circuit/Diy/Materials/Audiotransformer-AU/9041DMAU.htm

One of these may solve your problem.
Cheers.

 

[316a]

Transformers

I think this is probably a bit like winding audio transformers for a tube amp. Only hitch is that it uses higher voltages on the secondary and so insulation schemes will be more important.

Has anyone started winding an audio output transformer yet ?
If you have never wound a transformer - it might be much better to buy one.
Cheers.

Why not try using a 240V:6V mains toroid ? After all these should be able to provide wide bandwidth and a turns ratio of 1:40 . With an ESL , bass will not be required so core saturation will not be a problem , should work (in theory) .

Rarkov : I'm also building an ESL . A good source for mylar is model engineering suppliers . My 5 micron mylar was £5.00 for a 10mx30cm piece . Farnell have suitable double sided acrylic tape and foam tape suitable for spacer adhesive . Is this what you were planning on using ?

316a

 

[wrl]

$$$$

Wow, most of those transformers are well over $100 dollars.

I was hoping to spend no more than $75-$80 on each of them. Also, I don't need it to go lower than about 500-600 hz.

Anyone have any suggestions for places in the US?

Thanks,
Wes

 

[Alexander Rice]

Mains transformer

Using a mains transformer is probably not a good idea because thay are often made of the poorest grade of steel they can get away with. If you try feeding a mains transformer form a signal generator and measure the power in and out you find, unsurprisingly that they are most efficient around 50 Hz and drop off rapidly either side - i only tested to 1khz and already that was down by about 10dB from the 50hz peak - i dread to think what sort of thing happens at 20kHz. As frequency goes up you need thinner and thinner laminations to reduce eddy currents in the laminations. I would have thought you would be better re-winding an old output transformer.

 

[316a]

Re: Mains transformer

Using a mains transformer is probably not a good idea because thay are often made of the poorest grade of steel they can get away with. If you try feeding a mains transformer form a signal generator and measure the power in and out you find, unsurprisingly that they are most efficient around 50 Hz and drop off rapidly either side - i only tested to 1khz and already that was down by about 10dB from the 50hz peak - i dread to think what sort of thing happens at 20kHz. As frequency goes up you need thinner and thinner laminations to reduce eddy currents in the laminations. I would have thought you would be better re-winding an old output transformer.

I've built my ESL panels now and have already tried a mains toroid as a step-up transformer . Even though I need to do more work with raising the polarising voltage to increase sensitivity , there appears to be nothing wrong with using one , in fact the top-end in comparable , if not better than with an 8k anode to anode valve output unit . Due to the construction of mains toroids , wide bandwidth is achieved , of course with EI transformers you will run into problems ! Why not repeat your tests with a mains toroid , you'll probably get at least 30k bandwidth

316a

 

[Alexander Rice]

i did indeed test an EI type transformer - although the tests were not in connection with building speakers so i had no reason to retest a better trannie. I naturally assumed that the core geometry plays a relatively small part in the frequency response of the transformer, this may well not be true, althought i am sure it depends alot on the 'quality' of the particular transformer - ie. the type of steel used and the thickness of the laminations. That said, modern transformers with amorphous silicon steel laminations are already FAR superior to what was being used even 20 yrs ago. I'll run some tests tomorrow if i get the chance beacuse i have always been put off experimenting with valves due to the high cost of a suitable output trannie, if i can buy one 'off the shelf' in the form of an ordinary mains transformer or rewind one of the same to suit my needs i'll definitley be paying more attention to the possibility of home brewing a little valve amp (hell, i've got a 1000W trantmitting trode in the basement - that could make an 'interesting' amp...)

 

[316a]

Give it a try

Go for it , you may be surprised
This evening I discarded the stepup transformers altogether and drove the ESL straight from the anodes of my amp via teflon capacitors This is definitely the way to go ! Luckily I only need to drive a 5"x20" treble panel . My current workshop amp only runs from a 220V rail though , time to build something with higher B+ and drive these things active . Interestingly the sensitivity of the ESL can be matched to the main unit (Jordan JX92 TL) by tweaking the polaring bias . ESL's are fun

316a