Actual Plasma Tweeters

Massless Speakers Part 2


Dr. Siegfried Klein, The Ionovac and Magnat, 1946
The loudest plasma loudspeaker

There's a lot more material online about Dr. Siegfried Klein, rightly so, as he has contributed the most to the field of massless loudspeakers with two distinctly different commercial designs created over 4 decades.  He was a prolific inventor and developer of massless tweeters from the '50s through to the '80s.  Using the ions in the brand name of his first tweeter, the Ionophone is actually a plasma tweeter as was the later Magnat MP range of tweeters.

Siegfried Klein
Dr. Siegfried Klein
The earliest article from Klein was in L'Onde electrique in 1946, laying out the grounding for his first tweeter the Ionophone made by DuKane in 1951.  The first reviews in 1952 from the same magazine and also Wireless World were both favourable.

Klein's own paper in Acta Acusitca in 1954 was followed by 3 patents (with more in other countries) in 1956 and 1958.  He used these patents and intellectual property to license his designs for manufacture around the world by other companies.  These were notably the Electrovoice T-3500 in 1958 and Fane Acoustics Ionofane (and Ionofone depending on what you read) from 1960. The Ionofane was used by Bowers & Wilkins as the tweeter in their P-2-H loudspeaker and for a short period the Ionofane was licensed by Sony for sale in Japan.  Even as late as 1974 a German company called Tecnac created a clone.

The Ionofane

These were all based on the same basic design of a slim horn loaded quartz tube plasma generator and a valve based amplifier and RF biasing circuit.  This was an all in one assembly intended to be incorporated into a larger loudspeaker that had conventional dynamic midrange and woofer drive units for the lower frequencies.

All of these were moderately successful with perhaps almost 2000 sold, especially considering that this was an expensive option for a tweeter. Klein did well to exploit the intellectual property and properly license the design out to other companies.  This would be in ideal situation for an inventor who would like their invention to be manufactured around the world.  It would seem that these tweeters were manufactured up to the late 60's before interest slowly petered out, there's likely only a limited market for such a design before the market gets saturated.

In 1978 Klein took a different approach in a couple of ways, with a different design and this time teaming up with just one company.  This was also licensed for distribution in the USA in 1980 by Dahlquist Corp but they shelved it and customers there had to wait for Magnat USA to sell it years later in 1987.  The Magnat MP range of tweeters (patented across 1980,81 and 84) while also based on an RF circuit had the plasma struck across open electrodes surrounded by a distinctive ball shaped grounded mesh.  The mesh provided both a safe ground and RF shield.  Another inner silver plated shield acted to catalyze the ozone back to oxygen. The substantial black block base encased a solid state circuit and was intended to be placed on top of an existing loudspeaker rather than built inside the case.  L'Audiophile also gave this a positive review in 1980.

As the original Ionophone was created quite some time ago the patents and IP have been expired for a while.  Vaugn Loudspeakers recreated the Ionovac in 2016, with revised modernised circuitry and is now on sale as part of their full range speaker.

Part 3 - A Stiff Breeze

How Old?
Actual Plasma
A Stiff Breeze
Popular Plasma
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Future Thinking
 
 
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