10
CALIBRATION
The Sound Systems should be turned on for at least one
hour before alignment. All doors should be closed and the
exhaust fan should be running if the MOD V is placed in an
equipment rack.
Note: Before plugging or unplugging cards in the MOD V
during calibration, be certain power is removed from the
MOD V. Otherwise, damage to cards or the processor may
result!
EQUIPMENT REQUIRED:
Sound Pressure level meter, real time analyzer with a cali-
brated microphone, dual trace oscilloscope, multimeter, a
tuning wand and appropriate test loops.
B CHAIN CALIBRATION:
PRELIMINARY:
It is desirable to have a SMART PINK NOISE GENERA-
TOR CARD and, optionally, an EXTENDER CARD for
performing the calibration and testing of the MOD V. Note:
Make sure the SMART Pink Noise Generator Card has the
following minor modification: There must be a jumper wire
between pins 4 & 5 of the edge connector as viewed from
the component side. This allows the Surround switch to
simultaneously feed pink noise to both Left and Right
Surround channels. A future version of the Pink Noise
Generator card will have separate Left and Right Surround
switches.
The PINK NOISE card may be plugged directly in without
the extender card, but it is easier if the extender card is used
with the PINK NOISE card. The PINK NOISE card plugs
into the MATRIX CARD position for setting house EQ lev-
els and into the PREAMP CARD position for setting sub-
bass levels. The PINK NOISE CARD has seven switches.
The bottom switch is used to select NORMAL or CHOO-
CHOO modes. The top six switches are used to turn indi-
vidual channels on and off. These channel switches are
three position, with center position being off, the top posi-
tion giving an in phase signal and the bottom position giv-
ing an out of phase signal. There is a built-in high quality
pink noise source which feeds these switches.
If a Pink Noise Card is not available for the MOD V cali-
bration, then an external pink noise source may be used
instead. Feed the external pink noise source into the DIGI-
TAL inputs on the rear of the MOD V for the following
checks. Set the pink noise source level for .55 volts RMS.
You must use an analog meter to measure this voltage level.
Special Note: The factory settings for digital levels on the
External Input/NR Switching Card should be left as they are
while using an external pink noise source. This will ensure
that the house levels are set correctly. Normally, the digital
input levels on the External Input/NR Switching card do not
need adjustment, but if they must be adjusted, do so AFTER
setting house levels. See the DIGITAL LEVEL SETTINGS
at the end of the B CHAIN CALIBRATION section for
more information.
For the following procedures, select STEREO by pushing
the appropriate button on the front panel. Also, set the front
panel MASTER FILM FADER to the CAL line, and the
trim faders to the 12 o’clock position.
EQUALIZATION AND HOUSE LEVELS:
The equalizers are normally shipped with the individual
trimpots set for a flat frequency response. The 1/3 octave
equalizers used for the stage channels are capable of cutting
and boosting each frequency band ± 10 dB. The individual
trimpots are single turn types, with the mid position of each
pot being flat (unity gain).
The dual-channel surround equalizer card is a full octave
band type. All frequencies on this card are also cut and
boost ± 10 dB with single turn trimpots.
Remove the MATRIX CARD from its slot and set it aside.
Plug the PINK NOISE CARD into the MATRIX CARD
slot. Make sure the NORMAL/CHOO-CHOO switch is in
the NORMAL position. Turn on the appropriate switch on
the PINK NOISE CARD for the channel you wish to equal-
ize. Perform the equalization and then adjust the output
trimpot on the OUTPUT/MUSIC CARD so that 85 dBC spl
is measured in the auditorium. Do this for the five main
channels (Left, Center, Right, Left Surround & Right
Surround). If more gain is needed, then the gain pot on the
ISO Cinema playback standard states that 1/3 octave bands
should be tuned for flat response to 2 kHz, with a 3
dB/octave rolloff above 2K.
The optional extender card can be used with the Pink Noise
Card to calibrate the MOD V. This allows easier access to
the Pink Noise Card.
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