B&W electronics 70 User Instruction Handbook - page 9
- 9 -
It was further decided that the concept of Model 70 should
be one of an international product and, whilst paragraph two
detailing a high power handling capacity was consistent with
World markets, certain other design and constructional features
were laid down as being essential :-
a) That the system be in a modular form allowing
easy assembly by overseas agents.
b) That the bass chamber loading, consistent always
with the ultimate performance, be relatively
simple and capable of being accurately copied in
distant markets where it is obviously uneconomical
to ship complete systems.
c) As an extension of 2) that all units be easily
removable to facilitate speedy servicing in overseas
markets where technical service facilities are
limited.
DESIGN PERAMETERS
It has been generally accepted for reasons too well known
to be repeated that, if a loudspeaker system is aiming at
optimum performance, the frequency spectrum should be split.
The precise division of frequencies to be handled by the various
units and reasons for the crossover frequency chosen will be
discussed later in this release, but initially let us survey the
alternatives dealing first with frequencies below 400 H z .
The alternatives are electrostatic or moving coil units and
it was decided at an early stage in the design that the latter
method showed obvious advantages. For example, on an existing
full range electrostatic loudspeaker very careful measurements
were made and total harmonic distortion at 60 Hz with 15 watt
r.m.s. input was in the region of 50%. On an alternative full
range electrostatic American design which was sampled, the
dimensions of this unit were such as to exclude its use in the
majority of home installations. Whilst a very selected few may
accept panels in their lounge some seven feet high and three
feet Wide it was felt that on appearance alone the points
discussed in the introduction were in no way catered for.
As a result of long discussions between the writer and
Mr. Dennis Ward it was felt that the moving coil system should be