Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!rutgers!ucsd!ucsdhub!hp-sdd!hplabs!hpda!hpcuhb!hpscdc!rkarlqu
From: rkarlqu@hpscdc.HP.COM (Rick Karlquist)
Newsgroups: sci.electronics
Subject: Re: Flame Speaker Demo.
Message-ID: <5770013@hpscdc.HP.COM>
Date: 13 Sep 88 23:00:16 GMT
References: <3376@crash.cts.com>
Organization: Hewlett-Packard, Santa Clara Div.
Lines: 16

I think there is some confusion here between the flame loudspeaker
of Popular Electronics in 1968 (yes we built one in my high school 
too) and the corona wind speaker first described in 1955 or so.
The Ionovac and I believe the Magnat are corona wind speakers,
not flame speakers.  I have a copy of the original paper describing
the design.  You put high voltage bias across a spark gap creating
a corona wind.  You then modulate this corona wind with a "grid"
element which was actually a ring surrounding the spark gap.  The
audio connects to the "grid".  A serious disadvantage of the device
is the large amounts of ozone produced.  In 1955, they were still 
selling ozone generators to "freshen the air, like after a thunderstorm"
and only later learned that ozone is an irritant with no beneficial
health effects (unless its in the upper atmosphere :-(  

I wonder if there's some way to make a speaker out of those "negative
ion generators" that seem to have replaced ozone generators.