MartinLogan Center Channel speaker - Manual (Page 17)

Electrostatic Loudspeaker History 17
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 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 frequency reproduction, it
often found itself used in conjunction with woofers, most
notably, woofers 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 on electrostatic
loudspeaker design in Wireless World, a British electronics
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
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
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 electro-
static 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 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 addressed. 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, 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.