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).
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.
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).
An externally hosted image should be here but it was not working when we last tested it.
[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.
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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??
_-_-bear
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.
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?
_-_-bear
Guess that those have to be silk threads for the best sound?
_-_-bear
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.
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.
A single ended electrostatic driver was made in Japan by Sunsey and sold for a while in France around 1975-1980.
I just discover this site which may help :
Do It Yourself - Electrostatic Speakers
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Alex Shackman had a company called Southern Sound services, he made two versions of his electrostatic units a smaller one that crossed over at 1,000k i had a pair of these until quite recently, he advertised them as like a Quad but with better bass,
later on he made the larger version which this appears to be, this crossed over at 400cycles both with a Allen bextrene mid bass unit i think a 10 inch with the larger unit and an 8 with the smaller,
he sold them made up in a sealed box with lots of absorbent wadding behind the unit,
i bought the kit, no instructions except where the wire went i rang him and asked about the enclosure Alex replied about 1 to 2 cubic ft, but could not offer any other information on correct size loading etc,ft when Alex died sudenly his wife sold the rights to manufacture the units to Volt who made high quality bass units but they ceased making and selling them after just a few units,
i built a design called the badger from Hi Fi news (i think) and made the box sides deeper and mounted it in a tunnel above the bass midrange unit clarity was fantastic better than any cone unit on the market also sound stage was much wider as it is a dipole and radiated from the rear as well, i used these for about 15 years before giving them away when i moved abroad,
later on he made the larger version which this appears to be, this crossed over at 400cycles both with a Allen bextrene mid bass unit i think a 10 inch with the larger unit and an 8 with the smaller,
he sold them made up in a sealed box with lots of absorbent wadding behind the unit,
i bought the kit, no instructions except where the wire went i rang him and asked about the enclosure Alex replied about 1 to 2 cubic ft, but could not offer any other information on correct size loading etc,ft when Alex died sudenly his wife sold the rights to manufacture the units to Volt who made high quality bass units but they ceased making and selling them after just a few units,
i built a design called the badger from Hi Fi news (i think) and made the box sides deeper and mounted it in a tunnel above the bass midrange unit clarity was fantastic better than any cone unit on the market also sound stage was much wider as it is a dipole and radiated from the rear as well, i used these for about 15 years before giving them away when i moved abroad,
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I still have a pair of the smaller Shackman panels, which I bought from the man himself. He demoed them in a cabinet with a cone driver, and didn't like me questioning the obvious change from 'static to cone sound! Mine claim xover at 500Hz, but wouldn't fancy that.
I am making a pair of isobaric bass speakers, with KEF B139s, EJ Jordan JX125 wide range drivers and the Shackmans on top.
It will be interesting to see how that works out. Oh, and they are active too, transistor bass amps, 845 SET mids and EL 84 PP hf amps. Wish me luck.
john s -Did you use the piddly transformers they came with? As far as I recall, the impedance dropped to 1 or 2 ohms at 20kHz. I was thinking of buying a pair of Sowter transformers for mine, but that ups the cost a fair bit.
I am making a pair of isobaric bass speakers, with KEF B139s, EJ Jordan JX125 wide range drivers and the Shackmans on top.
It will be interesting to see how that works out. Oh, and they are active too, transistor bass amps, 845 SET mids and EL 84 PP hf amps. Wish me luck.
john s -Did you use the piddly transformers they came with? As far as I recall, the impedance dropped to 1 or 2 ohms at 20kHz. I was thinking of buying a pair of Sowter transformers for mine, but that ups the cost a fair bit.
Seems indeed like Shackmans to me. Bought a pair at his home in New Barnett around 1978, indeed loaded with speakers (and 19forties UK interior).
He sold them in conjunction with 8 inch Dalesford Bextrene woofers and a pair of 2 mH ferrite coils. The woofers still perform their daily duties in a friend's 2 way speakers.
I never managed to have The ESL units sound anything other than outright horrible. Unfortunately I threw them away before I could do proper SPL measurements with IMP from 1993 on.
The transformers were very tiny indeed, the whole high tenson section mounted on a shoddy piece of timber. There was a wirewound pot of questionable qulaity included for woofer level matching.
Ah, brings back some audio memories from the UK audio business as it was in the late seventies.
Eelco
He sold them in conjunction with 8 inch Dalesford Bextrene woofers and a pair of 2 mH ferrite coils. The woofers still perform their daily duties in a friend's 2 way speakers.
I never managed to have The ESL units sound anything other than outright horrible. Unfortunately I threw them away before I could do proper SPL measurements with IMP from 1993 on.
The transformers were very tiny indeed, the whole high tenson section mounted on a shoddy piece of timber. There was a wirewound pot of questionable qulaity included for woofer level matching.
Ah, brings back some audio memories from the UK audio business as it was in the late seventies.
Eelco
Yes mine had a small transformer i could never understand the circuit on this it had a slow 6 db roll off to try and integrate the two units, which i mounted as close as possible, it was recommended in the HI/FI press at the time that 12db would have been better, which volt did on the units they sold,
mine sounded great, fantastic detail and clarity, the change in crossover frequency may have been when he was trying to get them lower and eventually had to go to a larger size to get the HZ down to 400,which would mean a different circuit design, there were times depending on the singer mostly i seem to remember female voice when it was noticeable and the sound jumped from the cone to the shackman unit,
as Boden mentions it was mounted on a piece of chipboard, but no pot on mine, from what i understand there appear to be ongoing changes as he tried different things, he had removed the details from the tranny before selling them, and Richard Allan Dalesford cone units, (i had forgotten the actual name)
i don't think the quality of the tranny is that important its just a voltage step up device i would think any small toroid would do as long as it had the same turns ratio, from what i remember it's not in the signal path, it's just bias voltage for the stators,
the diaphragm was stretched by hand and held with pieces of celotape and could lose their tension,
John S
Mine use a diode/capacitor voltage multiplier to get the HT for the diaphragm, -
and a step-up transformer for the audio signal-
"8986 ESL Transformer 1:100 CT 300Hz
Designed for mid/high band use with a 300 Hz crossover. Rated at 2000 volts maximum output. Fully shrouded style S only. Size F
Price: £121.40"
It's the audio transformer that I would like to replace. If yours didn't use this system, how did they step-up the audio?
"8986 ESL Transformer 1:100 CT 300Hz
Designed for mid/high band use with a 300 Hz crossover. Rated at 2000 volts maximum output. Fully shrouded style S only. Size F
Price: £121.40"
It's the audio transformer that I would like to replace. If yours didn't use this system, how did they step-up the audio?
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