If the Column is to be used at a low power on a
constant-voltage, 70-volt system, a ShureA102A 70-Volt
Transformer must be connected between the amplifier
and Columns.
WARNING
If the A102A Transformer is to be mounted
to the Column, it should be positioned at
the lower rear, just above the jack panel,
in order to improve Column stability.
Note that the Transformer should also be electrically
located as close to the Column as possible; therefore
the optimum mounting location just above the jack
panel should be used. Mounting of the transformer
adds approximately 82 mm (31/4 in.) to the total depth
of the Column.
SR103 Column Installation
The SR103 Column may be operated free-standing,
or suspended by means of: (1) chains or armored
cable attached to the four mounting screws, one at
each upper and lower side corner (see Figure B), or
(2) a Shure Model A103A Wall Mount Speaker Column
Bracket. In operating the SR103 Column in a free-
standing mode, the same considerations should be
given regarding placement and security as were stated
for the SR102 Column: platform stability, minimal traffic
and air current avoidance. Use physical restraints if
necessary.
To suspend the Column, first loosen the 5/16-18
mounting screws at each side corner. (Note that these
four screws may be replaced by four 5/16-18 x 11/zV
eyebolts-not supplied-if desired.) To avoid the pos-
sibility of loosening of the mounting bolts or eyebolts
due to vibration, it is recommended that a commercial
sealant such as LOCTITE Grade C or pipe joint com-
pound be applied to the screw threads before tighten-
ing them. Be sure that the chain or cable used is of
sufficient strength to restrain the Column; at least
135 kg (300 Ib) test strength is recommended.
WARNING
It is extremely important that both the me-
thod of securing the chain or cable and the
mounting surface are adequate to support
the weight of the Column. Inadequate sup-
port in Column and wall/ceiling mounting
hardware, mounting chain or cable, or wall
or ceiling mounting surface may result in a
hazardousoperating condition. When mount-
ing the Column in a plaster, or plaster-
board, or other thinwall-type ceiling or wall,
be sure to fasten hardware to firmly sup-
ported studs or beams. A backplate secur-
ing the hardware on the opposite side of
the wall should be used if wall construction
permits.
Carefully attach the ceiling chains or cables to the
upper mounting screws at the desired height. Attach
the remaining wall or ceiling chains or cables to the
lower mounting screws, and draw them up to the wall
or ceiling to form the desired angle of the Column
toward the audience. Secure all chains or cables
firmly, and tighten the speaker mounting screws. (For
instructions on mounting the SR103 Column using
the wall bracket which permits 19O of horizontal pivot-
ing, 18O of tilt-up and 12O of tilt-down, refer to the data
sheet supplied with the bracket assembly.)
Checking Sound Coverage
When the Columns, amplifier and other equipment
have been installed and connected, apply a fairly con-
stant level signal to the system (preferably program
material) and walk around the audience area. Listen
for a smooth, even output from the Columns, with
minimal differences in volume and tone, and no dis-
tortion or "dead spots."
A
dead spot-for audio pur-
poses, an audience area where no sound is heard, or
where the sound level is appreciably lower than the
rest of the audience area
-
may mean that the
Columns are not covering that area, or that the Column
speaker wires are connected out-of-phase. Proper
phasing may be readily determined by checking the
connections to the terminal strips on each Column to
make sure they are the same, but inadequate coverage
generally requires repositioning the Columns. The dead
area should be carefully examined to determine that
the problem can be corrected without resorting to aux-
iliary speakers.
SERVICE INSTRUCTIONS
Speaker Servicing
1. Disconnect speaker cables from phone jacks and/
or terminal strip.
2. Using an ohmmeter, measure the resistance be-
tween the plus
(+)
and minus
(-)
terminal screws.
The dc resistance should be 11 to 15 ohms (16
ohms nominal impedance) when strapped for 25-
volt operation, and 44 to 60 ohms (64 ohms nomi-
nal impedance) when strapped for 70-volt operation.
3. The SR102 and SR103 Columns are symmetrical
and contain two identical "sets" of four speakers
(see Figure
K).
If a speaker is suspected of being
faulty, the fault may be localized to one of the
two sets of speakers as follows. With all strapping
removed, measure the resistance between the plus
(+)
and 3 terminals. A normal condition in the top
set of speakers is indicated by a nominal reading
of 26 ohms. Measure the resistance between the
negative
(
-
)
and 2 terminals. A normal indication
in the bottom set of speakers is indicated by a
nominal reading of 26 ohms.
4. To gain access to the individual speakers, remove
the six Phillips head screws securing each trim
strip to the front of the Column. The front-panel
grille and foam pad assembly can now be removed,
exposing the speaker configuration.
(NOTE: When removing the assembly, be careful
not to separate the grille from the foam pad.) Re-
move the vertical wood retainer strip spanning the
8-inch speakers.
5. When the faulty condition has been localized, re-
move the top or bottom &inch speaker, depending
