MartinLogan Source Speakers - Manual (Page 17)

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
conventional 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
electrical 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 vacu-
um tube. Before this, an electrical signal
could not be amplified. The loudspeak-
er, 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 (plas-
ma) 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”.
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
cut records through the electrostat, they were stunned and
impressed. The electrostat performed splen-
didly. 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.
T h e a c o u s t i c g r a m o p h o n e w a s
d e s t i n e d t o b e c o m e o b s o l e t e .
Due to Rice and Kellogg’s enthusiasm, they devoted a
considerable amount of time researching the electrostatic
design. However, they soon encountered the same difficul-
ties that even present designers face; planar speakers require
a very large surface area to reproduce the lower frequen-
cies of the audio spectrum. Because the management 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,
progress. However, during the late 1940’s, audio expe-
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.
Rice and Kellogg had
narrowed the field of
“contestants down” to the
cone and the electrostat.
Electrostatic History 17
E
LECTROSTATIC HISTORY