cepts were used in the first full-range, push-pull electro-
static loudspeaker capable of producing high acoustic
pressure levels, which was exhibited during a meeting of
The American Physical Society in January, 1953.
The Model Nine introduces almost no distortion at
all in the process of converting electrical signals to acoustic
signals, throughout its very wide frequency range, and
therefore tends to emphasize deficiencies in the performance
of associated equipment. It is incumbent upon the user to
employ only very high quality auxiliary equipment, and to
insure that program material is of commensurate quality,
if optimum enjoyment is to be derived.
NOTE
Low-frequency noise (turntable rumble, tape flutter, record
thumps ), even if it is inaudible, must be kept to a minimum.
Whereas such noise will cause the voice coil of a good electro-
dynamic woofer to wander or bob around within its air gap,
in the Model Nine it will tend to saturate the core of the signal
step-up transformers. The acoustic result in both instances is
the same, i.e., the response at low audible frequencies tends to
become intermittently non-linear, and audible distortion tends
to occur on high-level passages, when these include low-fre-
quency components.
All parts of the Model Nine will operate satisfactorily and
continuously under normal conditions in the home or studio.
Care should be taken, however, not to expose any portion of
the system to temperatures in excess of 110
0
Fahrenheit for
prolonged periods of time. None of its component parts are
affected by the moisture content of the air except when the
relative humidity approaches 100% at temperatures near
100
0
Fahrenheit. Any Model Nine so exposed may suffer a
temporary degradation of performance, but generally will need
only to be left in a suitable environment for a short period of
time to regain fully its original performance.
N. B. - Do Not expose the Model Nine to spray of any kind,
including the mist from aerosol bombs or manually sprayed
cleaning agents, insecticides, deodorizers, etc. 1f the rear grille
needs cleaning, it should be done only with a damp cloth .
•
4
.,
OPERATION
Figure 1: Installing the power supply on the terminal
board at .the base of the panel. Both locating pins
(indicated by arrows) should be engaged at the same
time.
Setting Up
A medium-size Phillips-head, and a small Phillips-head
screwdriver are the only tools required for assembly. After
each panel has been laid face down on a non-abrasive sur-
face, such as a rug, so that the terminal board on the black
base faces UP, the black satin-finish can which houses the
bias supply and step-up transformer network can be installed
with the large round-head wood screws that are packed
within the top of the large carton.
NOTE
The power supplies are interchangeable; however, the
proper installation of the cans on each panel is such that the
labels identifying Right and Left face UP when the panel
is in an upright position. An inspection of the geometry of the
base terminal board and the terminal boards in the cans will
disclose clearly which panel is to be equipped with the can
labelled Right and which one is to have the can labelled Left
installed on its base. The mating of the plugs and sockets of the
two terminal boards is automatic when the locating pins are
inserted into the second hole from the upper end of the flange
on each side of the can. Make sure that BOTH locating holes
are over the locating pins before lowering the cans into place.
DO NOT PLUG IN THE AC CORDS TO ENERGIZE THE
BIAS SUPPLY UNTIL AFTER THE CANS HAVE BEEN
INSTALLED ON THE BASES OF THE PANELS.
5
