[AMRadio] Followup: "Isophon Lautsprecher" Info

[Merz Donald S]

Is there nothing that you guys can't answer? After a while, I'd start to think that yunz (that's pure Pittsburgh-ese) were making this stuff up. But then I get valid links to accurate information on the web. Sheesh...

Craig Sawyers came up with the most thorough reply, complete with link. The speakers pictured look like a later model of the ones I have. Apparently these will require a bias voltage. 

Once again, thanks to all for your replies and help.
73, Don Merz, N3RHT

-----Original Message-----
From: greenkeys-admin at mailman.qth.net
[mailto:greenkeys-admin at mailman.qth.net]On Behalf Of Craig Sawyers
Sent: Monday, December 01, 2003 3:22 PM
To: greenkeys at mailman.qth.net
Subject: RE: [GreenKeys] What's A "Isophon Lautsprecher"?


In the 1950's Isophon produced a very high frequency electrostatic speaker
for 7kHz and upwards.  This was a single-ended design, which usually
produces quite a lot of distortion - but only if the diaphragm excursion is
large.  By limiting the frequency to the very upper end of the audible range
the excursion is kept to a few microns, keeping the distortion low.

There is a reference to these on
http://www.audiocircuit.com/9041-esl-circuit/Commercial/Isophon-ISO/9041CMISO.htm which also has links to specific designs with pictures.

Do these look anything like yours, Don?

Craig

> -----Original Message-----
> From: greenkeys-admin at mailman.qth.net
> [mailto:greenkeys-admin at mailman.qth.net]On Behalf Of Merz Donald S
> Sent: 01 December 2003 19:43
> To: amradio at mailman.qth.net; boatanchors at theporch.com;
> greenkeys at mailman.qth.net; 'Glowbugs (E-mail)
> Subject: [GreenKeys] What's A "Isophon Lautsprecher"?
>
>
> Hmmm...What I have here is 2 small packages about 3 inches square
> and 1 inch deep. The label on each one says "Isophon Lautsprecher
> St HB 7  S228". Inside each package is a 1/2 inch thick bakelite
> and aluminum assembly with a grille on one side and 2 wires on
> the other. The label on the back of each of these is the same as
> on the package. Molded into the back of each one is "Made in
> Germany". Hmmm...it doesn't say "made in West Germany" and it is
> too old to be made in post-USSR-breakup Germany. So I conclude
> that these were made in pre-war Nazi Deutschland.
>
> Anyone? Any Guesses? Any referrals to someone who might know?
> These were found in an estate in a paper Cameradio bag on which
> was written "electro-static".
>
> Any that's all the clues I've got to give you. Any help appreciated.
> Thanks.
> 73, Don Merz, N3RHT
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