The Versatile Projectors,
Screen and Sound
The Drake, Plymouth, England. Kinematograph Weekly, 12. June 1958
|Read more at
The 70mm Newsletter
The spacious projection room at the Drake, showing
the two Philips Multi -Purpose projectors installed by Brockliss.
INSTALLATION by J Frank Brockliss Ltd., of the
Philips Multi-Purpose 70/35-mm. projectors at the Drake is the third of
its kind that the company has done this year. "The others were at the
Dominion, Tottenham Court Road, London, and the Gaumont,
Manchester. The installations were supervised by Frank Durban, director
and general manager of Brockliss.
This Philips projector is the
only one designed to run either 70-mm. or 35-mm. film, the
interchangeability being vital, since it is not to be expected that
there will ever be a continual flow of films in Todd-AO. Conversion from
one gauge to another takes only a few minutes, so that films of both
gauges can be included on the same programme.
The steadiness of the picture in
the previous installations has been the subject of comment; measurements
of 50 projectors have shown that vertical jump does not exceed 0.15 per
cent., and side weave does not exceed 0.2 per cent.—both figures
considerably better than accepted tolerances.
More in 70mm reading:
The Drake, Plymouth, England
The Technical Side. We Aimed at
In harmony with the new City
Demonstration of Our Faith in the Future
The Saga of Todd-AO
DP70 / Universal 70-35 / Norelco AAII
- The Todd-AO Projector
The sharpness of the picture
owes much to the projector. Obviously an aperture width of nearly two
inches would lead to severe buckling of the film were it not for the
curvature of the gate. A major difficulty heretofore in the design of a
curved gate has been to secure the accurate matching of gate runners and
skates; in the Philips projector this difficulty is overcome by the use
of flexible steel strip for the skates, which are tensioned to provide
adequate friction. The skates extend well below the gate to guide the
film on to the intermittent sprocket—an important factor in maintaining
However, the cooling of the aperture plate plays an
important part in preventing heating of the film. A pipe surrounds the
aperture carrying cooling water; the use of heat-conducting metals for
the aperture insert encourages the dissipation of heat, and after a
20-minute run at maximum arc current, the temperature of the gate does
not exceed 65 deg F.
Yet another factor making for sharpness and
steadiness of the picture is the massive lens mount, which is made
possible by reason of the fact that the lens does not have to be lifted
to open the gate. The lens mount is built like a machine-tool, with a
fine-thread focusing screw and a strong spring to prevent back-lash.
manufactured by the American Optical Co., have been supplied by Brockliss. They are fitted with "minifiers" - negative attachments
which make it possible to use lenses of shorter focus and therefore
Turning to sound; the magnetic sound head has a
cluster of ten cores - six for Todd-AO and four for "CinemaScope". The
entire cluster is well shielded, and each head has a Response curve flat
to within ± 2 Db. up to a frequency of 12 kc/s.
Optical sound is, of course,
used only for 35mm. prints, and the sound head embodies the same
magnifying system as other Philips projectors.
Most installations of the
Philips Multipurpose projector in other countries embody the complete
Philips sound channel, but the versatility of the machine is
demonstrated by the fact that at the Dominion and the Gaumont,
Manchester, the sound heads feed into a GB-Kalee sound system, and at
the Drake into Westrex.
ANDREW SMITH HARKNESS LTD. has installed what is
certainly one of the largest screens in Great Britain, at the Drake,
The company has made a special Perlux screen to
measure 66 ft. x 27 ft. for fitting into a screen frame 67 ft. x 32 ft.
Apart from size, however, it is, undoubtedly, one of the most
outstanding installations in this country: the curvature and tilt can be
altered automatically from the projection booth, from 3 ft. curvature
for Anamorphic films to 8 ft. for Todd-AO presentation.
Harkness' Perlux-screen was
chosen because it is the screen most suitable for this installation: a
silver or aluminised screen is not suitable to a deep curve due to the
heavy falling off in brightness when viewed at angles. The Perlux finish
maintains screen whiteness at all angles and has a uniform brightness
when viewed from any part of the auditorium.
The five speaker towers are also
by Harkness, and the two outermost move with the screen when the curve
is altered. The screen frame is also fitted with adjustable side
THE SOUND SYSTEM
Drake has been equipped by Westrex with a sound system to complement the
facilities for projecting 70mm six-track magnetic film, 35mm four-track
magnetic film and 35mm photo-track film.
Five stage loudspeaker
assemblies are provided for six-track-magnetic film, the sixth track
feeding 24 two-way "ambient" loudspeakers surrounding the auditorium.
Each of the five stage loudspeaker assemblies uses
four low frequency units mounted in a dual horn assembly and two high
frequency units. Apart from the six monitor loudspeakers in the
operating box, the theatre uses a total of 44 low frequency units and 34
high frequency units. Since the screen frame is articulated the outer
stage loudspeaker assemblies are mounted on mobile towers.
In the operating box two banks
of magnetic pre-amplifiers and two photo-track preamplifiers with
push-button change-over between the banks feed six banks of power
amplifiers, each of 80 watts rating.
The sound main control unit
includes a six-gang potentiometer and a separate potentiometer for
photo-track sound together with the more usual switching facilities. The
control of sound level for any type of presentation can be passed from
the operating box to a corresponding unit in the auditorium located in
the centre of the balcony.
The mixer of a three-channel
stage amplification system is also embodied in the auditorium sound
control unit. The two-way loudspeakers for the stage amplification
system are arranged around the proscenium arch and are fed from an
independent amplifier system, the low level circuits of which embody
A hi-fi type double turntable disc reproducer can
feed either the stage or ambient loudspeaker systems through the main
An entirely independent inductive loop hearing-aid
system is provided which allows any seat in the greater part of the
total seating capacity of the theatre to be used by a deaf person. The
deaf person will receive sound through his own personal hearing aid if
it is of an appropriate and modern type.
If his hearing aid does not
possess inductive pick-up facilities, then these facilities can be
provided by special hearing aids using external earphones provided by
One of the Hewittic I80A
projection arc rectifiers that has been installed in Plymouth
HEWITTIC glass bulb rectifiers have been installed
in the Drake, Plymouth, for supplying the three Ashcraft Super Cinex
projection arc lamps and the two Stelmar spot-lamps.
The equipment comprises, for
each projection arc, a six-phase rectifier rated for a maximum output at
180 amps; and for the spot lamps, a twin circuit three-phase rectifier,
each circuit being rated for a maximum output of 80 amps. The rectifier
circuits in each case are of the choke-controlled type and supply the
arc lamps without the employment of any ballast resistance.
In the case of the projection
arc supply rectifiers, provision is made to cover an arc current range
of 130/180 amps, and the required arc current loading within this range
is pre-selected by means of a combination of transformer and choke
Provision is also made to give a reduced current
for striking the arc followed by a direct step up to the full running
value, these current values being obtained by means of remote control
One control panel is provided for each arc lamp,
and this includes the strike and run control switches and ammeter, and
voltmeter for measuring the arc current and voltage.
| || |
|Go: back - top - back issues - news index|