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
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 electro- statics 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 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, Beveridge, 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 dis- persion 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.
