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Installation
The S R l l 2 B and SR116B may be operated free-standing,
either on their own feet or on a Shure A112A Tilt Bracket,
or suspended on a wall or ceiling using an A112A or an
A112D Wall Mount Swivel Bracket. In positioning the
Speakers for optimum sound coverage, care must be
taken to locate the Speakers away from areas where
they may interfere with the movement of performers,
audience, curtains or stage sets.
If the Speaker is to be used at low power on a con-
stant-voltage, 70-volt system, a Shure Model A102A
70-Volt Transformer must be connected between the am-
plifier and Speaker. The transformer should be located as
close to the Speaker as possible; therefore the optimum
mounting location just above the connector panel should
be used. Mounting of the transformer adds approximately
82 mm (3Y4 in.) to the total depth of the Speaker.
Checking Sound Coverage
When the Speakers, 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 Speakers, with minimal
differences in volume and tone, and no distortion or
"dead spots." A dead spot-for
audio purposes, an
audience area where no sound is heard, or where the
sound level is appreciably lower-may
mean that the
Speakers are not covering that area, or that the speaker
wires are connected out-of-phase. Proper phasing may be
readily determined by checking the connections on each
Speaker, but inadequate coverage generally requires re-
positioning the Speakers. The dead area should be care-
fully examined to determine that the problem can be
corrected without resorting to auxiliary speakers.
SERVICE INSTRUCTIONS
Speaker Servicing
1. Disconnect speaker cables from phone jacks or
terminal strip.
2. Using an ohmmeter, measure the resistance be-
tween the plus ( + ) and minus ( - ) terminal screws
or tip and sleeve of phone jack. The dc resistance
should be 5.5 to 7 ohms.
3. To gain access to the individual speakers, remove
the grille by pulling the two cloth tabs at the bot-
tom of the grille. Remove the screws securing the
horn/baffle
board assembly. Remove the horn/
baffle board assembly, taking care not to stress
the wiring.
4. Using an ohmmeter, measure the resistance of each
speaker voice coil. A clicking sound will be made
by a "good" speaker when an ohmmeter is con-
nected or disconnected. Note that the resistance of
each 8-inch speaker cannot be measured without
disconnecting one lead connecting the two speak-
ers. Each 8-inch speaker should measure between
11 and 13 ohms. With its leads disconnected, the
high-frequency driver should measure between 6.7
and 7.7 ohms.
5. If the above tests do not locate the problem unit,
apply a small ac voltage from an oscillator and am-
plifier to each speaker individually (approximately
4V, 50 Hz to 5 kHz for 8-inch speakers; approxi-
mately 2V, 3 kHz to 15 kHz for high-frequency
speakers).
W A R N I N G
Sound pressure levels generated by this test may
be damaging to your hearing. Aim speakers away
from listeners and toward sound-absorbent material
(curtains, blanket, etc.). Carefully adjust test signal
amplitude to avoid unnecessarily high sound pres-
sure levels for prolonged periods.
As the test signal frequency is varied, any erratic
buzzes or rattles indicate possible failure.
6. Reconnect, replace and tighten the 8-inch speak-
ers. Reconnect the high-frequency driver and re-
place the horn/baffle board and grille. Tighten all
hardware to avoid rattles.
High-Frequency Driver Replacement
To replace the high-frequency driver, follow these steps:
1. Remove grille assembly and horn/baffle board as
described in Speaker Servicing.
2. Remove leads from driver terminals. Note color
coding of speaker wires.
3. For earlier production units, remove three 6-32 x
1
Ye
in. screws securing high-frequency driver to
horn/baffle board. For later production units, re-
move two 10-16 x 1 in. screws holding driver
mounting plate to horn/baffle board. Remove driver
mounting plate and driver from horn/baffle board.
4. Replace driver diaphragm and voice coil assembly
as described in High-Frequency Diaphragm and
Coil Replacement instruction sheet.
5. For earlier production units, carefully place repaired
or new high-frequency driver in position over horn/
baffle/board, taking care to line up holes in driver
over holes in horn/baffle board. Be sure that driver
terminals are positioned downward (toward low-
frequency speakers). Replace three 6-32 x 1 % in.
screws, and tighten high-frequency driver assembly.
6. For later production units, carefully place repaired
or new high-frequency driver in position over horn/
baffle board with driver terminals downward (toward
low-frequency speakers). Position driver mounting
plate over driver, lining up holes in mounting plate
over threaded holes in horn/baffle board. Replace
two 10-16 x 1 in. screws, and tighten securely.
7. Replace removed driver leads. Note polarity mark-
ing on driver.
8.
~ssemble horn/baffle board and grille to enclo-
?
and fasten securely to avoid rattles.
Nameplate
Should it become necessary to replace or re-fasten the
front-panel nameplate, be sure to use a heavy-duty
weather-resistant
adhesive.
Goodyear
PLIOBOND
or
equivalent cement is recommended.
ACCESSORIES
The following optional accessories are available for use
with SR112B and SRl16B Speakers:
A112A Tilt Bracket permits 360" rotation of the Speaker
about a horizontal axis. Heavy-duty tubular steel with a
flat steel baseplate that provides stable floor or shelf for
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