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Electrostatic Loudspeaker History 19
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 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 elec-
trostatic speaker on his own time. He
soon thought of insulating the stators to
prevent the destructive effects of arcing.
By 1952, he had an electrostatic tweeter
element ready for commercial produc-
tion. This new tweeter soon created a sensation among
American audio hobbyists. Since Janszen’s tweeter element
was limited to high frequency reproduction, it often found
itself used in conjunction with woofers—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 sur-
passed 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 electrostatics permit the use of diaphragms that are
low in mass, large in area and uniformly driven over their
surfaces by electrostatic 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 1960s 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 limitations as the Quad. The KLH 9 could
play markedly 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 speak-
ers. 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 elec-
trostatic panels for the Servostatic, a hybrid electrostatic
system that was Infinity’s first speaker product. Other
companies 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 progressed 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 concepts.
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 disper-
sion properties of early models have been addressed by
using delay lines, acoustical 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 loud-
speaker products ever built.