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MartinLogan Logos Руководство пользователя онлайн [5/22] 169956

Page 5

Logos User's Manual

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 electro-

static 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 loud-

speaker. 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 fre-

quency 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. How-

ever, in actual use the Quad had a few problems. It could

not play 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 han-

dling 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 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 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 electro-

static 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. Advance-

ments 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 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.

MartinLogan Logos Руководство пользователя онлайн [5/22] 169956

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