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28
In 1947, Arthur Janszen, a young Naval engineer, took part in
a research project for the Navy. The Navy was interested in
developing 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 con-
firmed 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 thought of insulating the stators to prevent the destruc-
tive effects of arcing. By 1952, he had an electrostatic tweeter
element ready for commercial production. This new tweeter
soon created a sensation among American audio hobbyists.
Since Janszen’s tweeter element was limit-
ed to high frequency reproduction, it often
found itself used in conjunction with woof-
ers—most notably, those from Acoustic
Research. These systems were highly
regarded by all audio enthusiasts.
As good as these systems were, they would
soon be surpassed by another electrostatic
speaker.
In 1955, Peter Walker published three articles regarding
electrostatic loudspeaker design in Wireless World, a British
magazine. In these articles, Walker demonstrated the benefits
of the electrostatic loudspeaker. He explained that electrostat-
ics permit the use of diaphragms that are low in mass, large
in area and uniformly driven over their surfaces by electro-
static forces. Due to these characteristics, electrostats have the
inherent ability to produce a wide bandwidth, flat frequency
response with distortion products being no greater than the
electronics driving them.
By 1956, Walker backed up his articles by introducing a con-
sumer product, the now famous Quad ESL. This speaker
immediately set a standard of performance for the audio
industry due to its incredible accuracy. However, in actual
use, the Quad had a few problems. It could not be played very
loud, it had poor bass performance, it presented a difficult
load that some amplifiers did not like, its dispersion was very
directional and its power handling was limited to around 70
watts. As a result, many people continued to use box speakers
with cones.
In the early 1960’s Arthur Janszen joined forces with the KLH
loudspeaker company, and together they introduced the KLH
9. Due to the large size of the KLH 9, it did not have as many
sonic limitations as the Quad. The KLH 9 could play marked-
ly louder and lower in frequency than the Quad ESL. Thus a
rivalry was born.
Janszen continued to develop electrostatic designs. He
was instrumental in the design of the Koss Model One, the
Acoustech and the Dennesen speakers. Roger West, the chief
designer of the Janszen Corporation, became the president
of Sound Lab. When Janszen Corporation was sold, the RTR
loudspeaker company bought half of the production tooling.
This tooling was used to make the electrostatic panels for the
Servostatic, a hybrid electrostatic system that was Infinity’s
first speaker product. Other com-
panies soon followed; each with
their own unique applications of
the technology. These include
Acoustat, Audiostatic, Beverage,
Dayton Wright, Sound Lab and
Stax, to name a few.
Electrostatic speakers have pro-
gressed and prospered because they actually do what Peter
Walker claimed they would. The limitations and problems
experienced in the past were not inherent to the electrostatic
concept. They were related to the applications of these con-
cepts.
Today, these limitations have been resolved. Advancements
in materials due to the U.S. space program give designers the
ability to harness the superiority of the electrostatic principle.
Today’s electrostats use advanced insulation techniques or
provide protection circuitry. The poor dispersion properties of
early models have been addressed by using delay lines, acous-
tical lenses, multiple panel arrays or, as in our own products,
by curving the diaphragm. Power handling and sensitivity have
also been increased.
These developments allow the consumer the opportunity to
own the highest performance loudspeaker products ever built.
It’s too bad Rice and Kellogg were never able to see just how
far the technology would be taken.
These developments allow the
consumer to own the highest
performance loudspeaker
products ever built.
English
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