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Page 4
Logos User's Manual
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
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 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
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 me-
dium.
By 1923, Bell Telephone Laboratories made the decision
to develop a complete musical playback system consist-
ing of an electronic phonograph and 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 collect-
ing 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.
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 genera-
tions 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
diaphragm, which was beginning to rot, was made of the
membrane of a pigs intestine that was covered with fine
gold leaf to conduct the audio signal.
When Rice and Kellogg began playing the new electri-
cally cut records through the electrostat, they were
shocked 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 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
difficulties that even present designers face; planar
speakers require a very large surface area to reproduce
the lower frequencies 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 thirty 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 gramo-
phones. Prior to the end of World War II, consumer audio
saw little, if any, progress. However, during 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.