Electrostatic History - Martin Logan Motif X Manuel De L'utilisateur

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leCtrostatIC HIstory
In the late 1800's, any loudspeaker was considered exotic. Today,
most of us take the wonders of sound reproduction 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 con-
ventional cone loudspeaker drivers that we know today.
However, Lodge had no intention for his device to reproduce
music because in 1898 there was no way to amplify an electri-
cal signal! As a result, his speaker had nothing to offer over the
acoustical gramophones 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 amplified. 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 mechan-
ically cut record and possessed almost
30 dB of dynamic range. The acoustical
gramophone couldn't begin to repro-
duce 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, the decision was made to develop a complete musi-
cal playback system consisting of an electronic phonograph
and a loudspeaker to take advantage of the new recording
medium. The project to two young engineers, C. W. Rice and
E. W. Kellogg.
Rice and Kellogg had a well equipped laboratory at their dispos-
al. This lab possessed a vacuum tube amplifier with an unheard
of 200 watts, a large selection of the new electrically cut pho-
nograph records and a variety of loudspeaker prototypes that
had been collecting over the past decade. Among these were
Lodge's cone, a speaker that used compressed air, a corona dis-
charge (plasma) speaker, and an electrostatic speaker.
After a short time, Rice and Kellogg had narrowed the field of
"contestants" down to the cone and the electrostat. The out-
come would dictate the way that future generations would refer
to loudspeakers as being either "conventional" or "exotic".
Their electrostat was something to behold. This enormous bipo-
lar speaker was as big as a door. The diaphragm, which was
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Electrostatic History

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
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 system sounded like real music rather than the honking,
squawking rendition of the acoustic gramophone. Immediately,
they knew they were on to something big. The acoustic gramo-
phone was destined to become obsolete.
Due to Rice and Kellogg's enthusiasm, they devoted a consid-
erable amount of time researching the electrostatic design.
However, they soon encountered the same difficulties that even
present designers face; planar speakers require a very large
Rice and Kellogg had
narrowed the field of
"contestants down" to the
cone and the electrostat.
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, progress. However, dur-
ing the late 1940's, audio experienced 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.
In 1947, Arthur Janszen, a young Naval engineer, took part in a
research project for the Navy. The Navy was interested in devel-
oping a better instrument for testing microphone arrays. The test
instrument needed an extremely accurate speaker, but Janszen
found that the cone speakers of the period were too nonlinear
in phase and amplitude response to meet his criteria. Janszen
believed that electrostats were inherently more linear than cones,
so he built a model using a thin plastic diaphragm treated with a
conductive coating. This model confirmed Janszen's beliefs, for it
exhibited remarkable phase and amplitude linearity.
Janszen was so excited with the results that he continued
research on the electrostatic speaker on his own time. He soon
surface area to reproduce the lower fre-
quencies of the audio spectrum. Because
the management considered large speak-
ers unacceptable, Rice and Kellogg's work
on electrostatics would never be put to use
for a commercial product. Reluctantly, they
advised management to go with the cone.
For the next 30 years, the electrostatic
design lay dormant.