Theatre Design & Technology - Dec 1974 - 25

TECHNICAL REPORTS

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THE GOLD EN GATE: AN ICELANDIC LEGEND MEETS THE AIRCORE TRANSFORMER
R. L. LOR EMAN

MAR lET TAC0LL EGE

When Marietta College decided to stage David
Stafanssen's The Golden Gate, a unique technical
problem presented itself. This dramatization of an
Icelandic legend requires a talking bag to interact
with various people during about three-quarters of
the play. The small burlap sack represents the soul of
Jon, the crusty husband of a simple religious woman,
Gunnar, determined to get her deceased husband
into Heaven b
ersonall trans ortin his unre entant soul up the mountain to the Golden Gate. The
play has been produced only a few times in
Iceland, Norway, and England - but never before in
America and no record was found to indicate how
this trick was staged, or if any attempt was made to
make the bag really talk.
Production discussions quickly produced several
requirements that clearly eliminated any system of
hiding loudspeakers or actors in the scenery or
wings. Gunnar was to carry the bag, place it in
various locations, and finally throw it through the
Golden Gate. During the course of the play the
"soul" had to speak 140-odd lines. These speeches
had to seem alive and spontaneous, from a point
so.urce, and be capable of movement about the stage.
The very character of Jon had to be embodied in that
small burlap sack which Gunnar was to carry and
protect from the "Enemy" (devil). In short, the bag
had to really talk.
Whatever the solution to this problem, there was
very little budget to cover expensive equipment.

solution were introduced: The volume and power had
to be controlled from the transmission end, and the
bag had to respond as if alive without any volume
adjustments being made on stage.
This led to the making of a large air-core transformer. The circuit for the whole system is shown in
simple form in Figure 1. The entire 20 x 30 ft. acting
area became the primary winding. It required about
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make an impedance load of 8 to 10 ohms. This was
wound around the stage perimeter, covered with
masonite strips, and connected to the 8 ohm speaker
output of a 10-watt PA amplifier already on hand.
This proved capable of inducing a weak, but usable
signal in a secondary coil placed anywhere within the
primary winding.
A standard telephone pickup coil was used as a
secondary winding. The signal induced in the
secondary coil was fed to an inexpensive converted
intercom station used as a pre-amp for a 2-watt I. C.
amplifier which fed a 4-inch speaker. All this was
fitted inside a homemade peg-board box, 6V2" x 7" x
3" (Figure 2), which could easily be carried in the
small burlap bag.
Experiments showed the only consideration limiting the size of the container was proximity of the
pickup coil and speaker windings. These elements
had to be about 3V2 inches apart to prevent
interaction.
The resulting capacity of this device proved quite
satisfactory. The actor playing Jon could speak into a
microphone from a position where he could see the
stage and react to both visual and audible cues,
projecting his voice to the bag via the primary
winding which would induce a signal in the secondary coil anytime it was within the area circumscribed by the primary winding.

Trailing a wire to the bag was clearly out of the
question. Citizen Band radio was not acceptable
because of poor quality and the likelihood of
unexpected intrusion on the channel used. The next
possibility seemed to be the so-called "wireless"
microphones. AM was eliminated because of poor
transmission quality, and experiments with FM
proved disappointing. Since FCC regulations severely limit the transmission power of "wireless"
microphones, the power to fill the house with sound
had to be at the receiver. This required using a large
FM receiver with an extended antenna and produced
an audible "white noise" unless the level was turned
down when the bag was not talking.

There was no audible hum, static, or other
extraneous noise in the system. Volume was completely controlled from the offstage position and no
adjustment was required in the pickup half of the
system other than to turn on the power supply before
it was carried on stage.

Thus two more important requirements for the

Signal strength was nominally uniform over about

THEATRE DESIGN AND TECHNOLOGY

DECEMBER. 1974

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