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Old 8th November 2012, 12:40 PM   #1
HiQual is offline HiQual  United Kingdom
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Default Can U identify these electrostatic units ?

Hello
I was a speaker designer for Cambridge Audio in my youth, working on R50's and R40's and newer designs.
In my earlier student days (early 70's) my first purchased speakers were a pair of hybrid electrostatics that included the upper mid to high end units pictured here and sourced from a dealer located in North London suburbs (I think).
Click the image to open in full size.[sorry, original picture location no longer available - see post #33 for new picture]
I quickly blew the bass units at a student party but the electrostatics were incorporated into subsequent builds over many years. They still sound superb and so I cannot bring myself to throw them away. However I am very curious to know more about them and their design principles. For example there are only two wires, which go to the stators - none to the membrane driver. They are about 8 inches 20cm high.
Can anyone provide any information?
I have the wiring diagram if anyone is interested in seeing it.
Many thanks.

Last edited by HiQual; 29th March 2013 at 05:13 PM. Reason: Original link location no longer available
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Old 8th November 2012, 02:13 PM   #2
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Sure, wiring diagram would be good.

If it has no HV supply then it is an electret type speaker - the diaphragm's molecular make up causes it to keep a charge, ie. self biased.

Pioneer had some tweeters that worked on this principle.

If it has HV, then it is likely a single ended ESL, less linear than P-P types, but they can work. There wre some German units, maybe Grundig or another famous brand I can't recall that made some 2" or so round tweeters like that...

The curve is interesting, what is being done to maintain the diaphragm separation??

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Old 8th November 2012, 02:36 PM   #3
HiQual is offline HiQual  United Kingdom
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Quote:
Originally Posted by bear View Post
Sure, wiring diagram would be good.

If it has no HV supply then it is an electret type speaker - the diaphragm's molecular make up causes it to keep a charge, ie. self biased.

Pioneer had some tweeters that worked on this principle.

If it has HV, then it is likely a single ended ESL, less linear than P-P types, but they can work. There wre some German units, maybe Grundig or another famous brand I can't recall that made some 2" or so round tweeters like that...

The curve is interesting, what is being done to maintain the diaphragm separation??

_-_-bear
Thank you very much bear - that is very interesting.
There is High Voltage - per the wiring diagram (see attached pdf file) - so I conclude it is a single ended ESL.
Diaphragm appears to rest directly on the back plate (but i am guessing, because it was never dismantled that far) and is covered with what appears to be fine string/twine to hold off the front plate.
Originally the front plate was simply clamped onto the backplate (you can see the screw holes in the picture) with 4 small insulated pieces of metal, but the gap was not even, so I dispensed with them and stuck the front plate back on with "blue-tack"!! that was many years ago and it has worked fine ever-since.
Thanks again for the information.
PS please excuse crude wiring diagram - please do not hesitate to ask for further information.
Attached Files
File Type: pdf Electrostatic Circuit.pdf (197.7 KB, 82 views)
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Old 8th November 2012, 07:12 PM   #4
VaNarn is offline VaNarn  Australia
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The ESS shown could be a model manufactured by L.G.Woollett in the early '60's.The address was 21 Anerley Station Road,London.
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Old 8th November 2012, 07:21 PM   #5
tinitus is offline tinitus  Europe
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Quote:
Originally Posted by VaNarn View Post
The ESS shown could be a model manufactured by L.G.Woollett in the early '60's.The address was 21 Anerley Station Road,London.
straight aussie shot, right from the hip...
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Old 8th November 2012, 09:45 PM   #6
HiQual is offline HiQual  United Kingdom
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Quote:
Originally Posted by VaNarn View Post
The ESS shown could be a model manufactured by L.G.Woollett in the early '60's.The address was 21 Anerley Station Road,London.
Many thanks VaNarn. I will see what Google shows up.
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Old 8th November 2012, 10:45 PM   #7
sreten is offline sreten  United Kingdom
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Hi,

look like Shackmans to me, they were single ended not push pull.

rgds, sreten.
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Last edited by sreten; 8th November 2012 at 10:49 PM.
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Old 9th November 2012, 11:54 AM   #8
Calvin is offline Calvin  Germany
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Hi,

first thought was :"Shackmans", but somehow I dismissed it. After digging deep in my dungeon of sources I find that it could indeed be an Shackman (Dynastat).
The spacers were made from the brown threads one can see on the backside stator.

jauu
Calvin
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Old 9th November 2012, 12:31 PM   #9
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The threads are very clever... but I'd guess that the diaphragm could get stuck at times where the straight line of the diaphragm is closest to the back curve... of course not if it is SE, because the back side would be at ground I presume?

Guess that those have to be silk threads for the best sound?

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Old 9th November 2012, 01:08 PM   #10
HiQual is offline HiQual  United Kingdom
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And the prize goes to .... (10 second pause) ... Calvin - thank you very much.
I have spent a few hours on google and there is a lot of info available.
For example a German company Shackman-Reromanus makes a modern version.
Mine are Shackman Dynastat MHT-85 Mid/Tweeter units.
I think the man that sold the original hybrid speakers to me was Mr Shackman himself in what appeared to be his front room (aka lounge) littered with speakers to do comparisons with.
Thank you everybody for helping me out - any suggestions on how to very simply deploy them in the future would be most welcome. Note I now have no workshop facility and very limited tools.
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