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In 1947, Arthur Janszen, a young Naval engineer, took part
in a research project for the Navy. The Navy was interest-
ed
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
peri-
od were too nonlinear in phase and amplitude response
to
meet his criteria. Janszen believed that electrostats were inher-
ently 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 thought of insulating the stators to
prevent the destructive 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 limited to high fre-
quency 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 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
consumer 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 dif-
ficult 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
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 speakers. Roger West,
the chief designer of the Janszen
Corporation, became the presi-
dent 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 princi-
ple. Today’s electrostats use advanced insulation techniques
or provide protection circuitry. The poor dispersion proper-
ties 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.
18 Electrostatic History