B&W electronics 70 User Instruction Handbook - page 11
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decision to be taken that the Electrostatic transducer, subject
to performance being the first consideration and price secondary,
was the best method to approach the final design. The
following conditions on the basic design were, therefore,
decided upon :-
1) That the bottom four octaves should be dealt with
by Moving coil unit and that a development
programme be launched to meet the stringent
requirements laid down.
2) That an Electrostatic transducer be developed
for frequencies above 400 Hz with the possible
addition of a "super tweeter", should this be
found to be necessary. That within this basic
design considerable work would be needed in
terms of improved distribution pattern and
increased power handling capacity on Electrostatic
units. Existing samples which were measured
showed this to be two of their weaker features.
DETAILED DISCUSSION ON BASIC UNITS FORMING THE
COMPLETED MODEL 70 SYSTEM
Mid High Frequency Electrostatic Unit.
It is not the intention of this release to provide
production techniques or information which have been expensive
both in terms of time and effort and which have made it
possible for us to successfully manufacture an Electrostatic
unit. Sufficient to say that at an early stage full reference
was made to all existing patents on Electrostatic units as it
was in no way our intention to infringe these and to produce
new material on which we ourselves could lay patent claims.
The problems which we overcame concerned such matters as
diaphragm stability, methods of diaphragm coating, A.C.
protective insulation as between fixed plates, mechanical
stability and many other factors which, to the uninitiated, may
seem simple but formed a major part of the considerable
development expense in which we have been involved.