Warwick University have developed a flat speaker - I don't know how it differs from the NEXT flat speaker panels but may be f interest to those here http://www2.warwick.ac.uk/newsandevents/pressreleases/?newsItem=094d43f62056911801205e116e1d7a35
And here: http://www.warwickaudiotech.com/
And here: http://www.warwickaudiotech.com/
Electrostatic audio loudspeakers US patent 7095864.html
"An electrostatic transducer, such as a loudspeaker or microphone, comprises a multi-layer panel (1) incorporating an electrically insulating middle layer (2) sandwiched between first and second electrically conducting outer layers (3, 4). At least one of the layers has a profiled surface (6) where it contacts the surface of another of the layers. Furthermore a signal generator is provided for applying an alternating electrical voltage across the first and second layers (3, 4) to initiate vibration due to variation of the electrostatic forces acting between the layers, thereby serving as a loudspeaker (or for detecting variation of such electrostatic forces due to received vibration in the case of a microphone). Such a transducer can serve as a low cost audio loudspeaker which can be made lightweight and flexible so as to render it suitable for a wide range of applications, for example to provide sound reproduction in a home environment without requiring any bulky enclosure, or in a notebook computer or mobile telephone."
Regards
James
"An electrostatic transducer, such as a loudspeaker or microphone, comprises a multi-layer panel (1) incorporating an electrically insulating middle layer (2) sandwiched between first and second electrically conducting outer layers (3, 4). At least one of the layers has a profiled surface (6) where it contacts the surface of another of the layers. Furthermore a signal generator is provided for applying an alternating electrical voltage across the first and second layers (3, 4) to initiate vibration due to variation of the electrostatic forces acting between the layers, thereby serving as a loudspeaker (or for detecting variation of such electrostatic forces due to received vibration in the case of a microphone). Such a transducer can serve as a low cost audio loudspeaker which can be made lightweight and flexible so as to render it suitable for a wide range of applications, for example to provide sound reproduction in a home environment without requiring any bulky enclosure, or in a notebook computer or mobile telephone."
Regards
James
Thanks for that. In 1969 I built David B. Weems' "wild woofer" and CTS had some electrostatic tweeters (exactly as pictured in the patent) for $1 or so each in their catalog. A thin sandwich of felt and some gold sputtered film, I never got the transformer to make them work but the "data sheet" had pictured directly rectified 220 mains as a bias supply. 
They use 200V because they are so thin but doesn't that mean the displacement is small? SY?
They use 200V because they are so thin but doesn't that mean the displacement is small? SY?
Here is the other thread, same subject
http://www.diyaudio.com/forums/showthread.php?s=&threadid=141831&highlight=
dave
http://www.diyaudio.com/forums/showthread.php?s=&threadid=141831&highlight=
dave
Its a good idea. I've long wondered why electro-statics weren't done this way. Its simply an electro-static membrane on a fixed set of substrates. Usually one wants the restoring force to be just the tension in the membrane but thats not necessary. HOWEVER, the efficiency is directly dependent on the stiffness of the insulator and an insulator HAS TO BE stiffer than air. Hence, I'm betting that the resulting transducers are very inefficient. But of course this can be made up for by size. But size is cost and cost is limiting. SO in the end you have just another way to do an electrostatic loudspeaker, but its the same size and cost of its predecessors - no big gains.
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