USL CM-680 - Manual (Page 12)

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CM-680 I NSTRUCTION M ANUAL Ultra Stereo Labs, Inc.
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CM-680 I NSTRUCTION M ANUAL Ultra Stereo Labs, Inc.
You will need to supply the following materials:
• Shielded audio cable for connecting the CM-680 to the
cinema processor and power amplifier outputs.
• Four 10-32 x 1/2" screws to mount the CM-680 in the audio
equipment rack.
FEATURES
The CM-680 monitor has the following standard features:
• Eight-Channel Monitoring - allows you to monitor either the
processor or power amplifier outputs to left, center, right,
surround left, surround right, back surround left, back surround
right and subwoofer channels, in any combination via the switch
on the front panel (see illustration on pg. 5 - switch 5)
• Input levels from processor and power amplifier can be
adjusted independently - no huge level jumps when switching
between processor and power amplifiers.
• Bargraph display may be calibrated to the reference level
for your theatre – the projectionist can see auditorium levels
instantly.
• Designed to work with bi-amplified sound systems to
monitor the high and low frequency outputs from the left,
center and right channels.
Crossover Setup
Analog Crossover Card XTA-680: When using the USL, Inc. Crossover
card, the following parameters must be set: time delay, crossover frequency,
horn EQ, Screen EQ and output levels. See figure #6.
Make sure the NORMAL/BYPASS switch is set in the NORMAL position.
Determine the model number of the speaker system being used. (Figure #7
has a listing of several popular cinema loudspeakers.)
If your loudspeaker requires a 1.8 ms delay, turn “ON” all DIP switches on
the first row marked 1.8 ms. Refer to figure #7. Likewise a loudspeaker
requiring 1.4 ms delay should require all the DIP switches in the second row
to be turned “ON”.
For loudspeakers requiring only 0.7 ms delay, leave all the time delay DIP
switches “OFF”. Never turn on both rows of time Delay switches!
Next, set the crossover frequency. For 800Hz, turn all the crossover frequency
DIP switches in the first row “ON”. For 500Hz, turn all the DIP switches in
the second row “ON”. For 330Hz, turn all the DIP switches in the third row
“ON”. For 297 Hz, leave all the crossover frequency DIP switches “OFF”.
Never turn on more than one row of DIP switches.
Now, set the horn EQ and screen EQ DIP switches. Generally, all six DIP
switches should be “ON”. In some cinemas, the left and right speakers are
mounted outside the screen area. In this case, turn the left and right screen
EQ switches to “OFF”. Some high frequency horns are very flat to 20kHz.
In this case, you may want to turn the horn EQ switches to “OFF”. The horn
and screen EQ each provide about 8dB of boost at 20kHz. The combination
of horn and screen EQ results in about 16 dB boost at 20kHz.
Finally, set the output levels. Using a Real Time Analyzer and feeding a pink
noise signal from the cinema processor, set the appropriate ten turn pots
for a flat response around the crossover frequency and a total SPL level of
“85” on each of the front three channels. There should be enough range in
the output pots to allow setting the amplifier gains at maximum or at the 12
O’clock position.
The bypass crossover is fixed at about 500 Hz with no time delay. Using a
Real Time Analyzer and feeding pink noise from the center channel of the
cinema processor, set the bypass levels for flat response around 500 Hz
and an SPL level of 85. The NORMAL/BYPASS switch will need to be set
in BYPASS.