B&W electronics dm70 Instruction Manual - page 16
A prime design p o i n t of the 701 is that it is
free-standing. This makes it possible easily
to remove the unit in the event of damage
etc., and service being required, thus avoid-
ing the transportation of entire heavy and
bulky system.
Crossover and Filter U n i t
The 500 Hz. crossover frequency between
the DW13/5 bass u n i t and the 701 electro-
static unit ensures that both these transducer
elements operate over their o p t i m u m fre-
quency ranges. Care has been taken in the
design of the low-pass section of the f i l t e r
to ensure that m a x i m u m amplifier damping
may be transferred to the bass unit by the
use of heavy gauge copper in the series in-
ductor, over a ferrite core. In addition, an
impedance- and level-controlling transformer
forms a part of the bass unit filter.
The power supply and high-pass filter for
the 701 electrostatic unit is solidly and
safely housed in a steel case. The mains lead
is captive, f o r safety.
Cabinet
The cabinet is constructed of 25mm chip-
board; in the case of the " C o n t i n e n t a l "
version, the curved f r o n t f o r m e d f r o m 19mm
p l y w o o d . The grille materials (earthed metal,
f r o n t and rear f o r the electrostatic) have
been chosen to give minimal deterioration
of the acoustic performance.
The " S t a n d a r d " version of the cabinet is
available in teak or walnut veneers and a
choice of walnut veneer or satin w h i t e finish
f o r the " C o n t i n e n t a l s . "
Acoustic Loading
The acoustic loading for the bass drive u n i t
is of the " i n f i n i t e b a f f l e " t y p e , synthetic
damping material being used to achieve
o p t i m u m system " Q " . A resonance-control-
ling removable pad is fitted to the rear of
the electrostatic.
Sensitivity
17 watts into nominal impedance required
to produce a sound level of 95 dB. at one
metre at 4 0 0 Hz
Power Handling
The D M 7 0 is suitable f o r high quality amp-
lifiers w i t h true RMS o u t p u t s of between
25 and 100 watts, w i t h double fuse pro-
tection on C and CA versions.
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Electrostatic Unit model 701