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e
leCtrostatIC HIstory
In the late 1800's, any loudspeaker was considered
exotic. Today, most of us take the wonders of sound repro-
duction for granted.
It was 1880 before Thomas Edison had invented the first
phonograph. This was a horn-loaded diaphragm that
was excited by a playback stylus. In 1898, Sir Oliver
Lodge invented a cone loudspeaker, which he referred to
as a "bellowing telephone", that was very similar to the
conventional cone loudspeaker drivers that we know today.
However, Lodge had no intention for his device to repro-
duce music because in 1898 there was no way to amplify
an electrical signal! As a result, his speaker had nothing
to offer over the acoustical gramo-
phones of the period. It was not until
1906 that Dr. Lee DeForrest invented
the triode vacuum tube. Before this, an
electrical signal could not be ampli-
fied. The loudspeaker, as we know it
today, should have ensued then, but
it did not. Amazingly, it was almost
twenty years before this would occur.
In 1921, the electrically cut phonograph record became
a reality. This method of recording was far superior to the
mechanically cut record and possessed almost 30 dB
of dynamic range. The acoustical gramophone couldn't
begin to reproduce all of the information on this new disc.
As a result, further developments in loudspeakers were
needed to cope with this amazing new recording medium.
By 1923, Bell Telephone Laboratories made the decision
to develop a complete musical playback system consisting
of an electronic phonograph and a loudspeaker to take
advantage of the new recording medium. Bell Labs
assigned the project to two young engineers, C. W. Rice
and E. W. Kellogg.
Rice and Kellogg had a well equipped laboratory at their
disposal. This lab possessed a vacuum tube amplifier
with an unheard of 200 watts, a large selection of the
new electrically cut phonograph records and a variety of
loudspeaker prototypes that Bell Labs had been collecting
over the past decade. Among these were Lodge's cone,
a speaker that used compressed air, a corona discharge
(plasma) speaker, and an electrostatic speaker.
14
Electrostatic History
After a short time, Rice and Kellogg had narrowed the
field of "contestants" down to the cone and the electrostat.
The outcome would dictate the way that future generations
would refer to loudspeaker as being either "conventional"
or "exotic".
Bell Laboratory's electrostat was something to behold. This
enormous bipolar speaker was as big as a door. The dia-
phragm, which was beginning to rot, was made of a pig
intestine that was covered with fine gold leaf to conduct
the audio signal.
When Rice and Kellogg began playing the new electrically
Rice and Kellogg had
narrowed the field of
"contestants down" to the
cone and the electrostat.
The acoustic gramophone was destined to become obsolete.
Due to Rice and Kellogg's enthusiasm, they devoted a
considerable amount of time researching the electrostatic
design. However, they soon encountered the same diffi-
culties that even present designers face; planar speakers
require a very large surface area to reproduce the lower
frequencies of the audio spectrum. Because the manage-
ment at Bell Labs considered large speakers unacceptable,
Rice and Kellogg's work on electrostatics would never
be put to use for a commercial product. Reluctantly, they
advised the Bell management to go with the cone. For the
next 30 years, the electrostatic design lay dormant.
During the Great Depression of the 1930's, consumer audio
almost died. The new electrically amplified loudspeaker
never gained acceptance, as most people continued to
use their old Victrola-style acoustic gramophones. Prior to
the end of World War II, consumer audio saw little, if any,
rienced a great rebirth. Suddenly there was tremendous
interest in audio products, and with that, a great demand
for improved audio components. No sooner had the cone
become established than it was challenged by products
developed during this new rebirth.
cut records through the electrostat,
they were stunned and impressed. The
electrostat performed splendidly. They
had never heard instrumental timbres
reproduced with such realism. This sys-
tem sounded like real music rather than
the honking, squawking rendition of the
acoustic gramophone. Immediately, they
knew they were on to something big.
progress. However, during the late 1940's, audio expe-
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