13
INSTALLATION & OPERATION
position.
EQUALIZATION AND HOUSE LEVELS:
The equalizers are normally shipped with the
individual trimpots set for a flat frequency
response. The optional 1/3 octave equalizers used
for the stage channels are capable of cutting and
boosting each frequency band ± 10 dB. The indi-
vidual trimpots are single turn types, with the
mid position of each pot being flat (unity gain).
On the standard one octave equalizer cards, all
frequencies are cut and boost ± 10 dB with single
turn trimpots also.
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 equalize. Perform the equaliza-
tion (see diagram 3) and then adjust the output trim-
pot on the OUTPUT/MUSIC CARD so that 79 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 stage EQs
can be used which
gives an additional
6 dB of gain.
However, do not
boost the gain on
the EQ cards unless
it is absolutely necessary.
The optional 1/3 octave stage channel equalizers in
the MODIIB allow the same tuning results obtained in
professional room tuning filter sets used in high-end
sound playback applications. Sound contractors
learned, a long time ago, that boosting frequency
bands adjacent to bands that are cut introduce a phase
shift that the ear is very sensitive to. Although the test
instruments show a nice curve, the sound has a col-
oration that is not natural. For this reason, we encour-
age you to apply the minimum amount of boost and
cut whenever needed. Never over-equalize the sys-
tem. All frequencies may be cut and boosted by as
much as 7 dB in each of the 1/3 octave bands without
creating the above problems. The use of bass and tre-
ble controls on the equalizer has also been avoided to
further minimize phase shift. Each filter section uses a
single turn trimpot for adjustment. The equalizers are
factory set for a flat response during final QC test.
Before attempting to equalize be sure the stage speak-
er connections are properly polarized, the polarity of
the components in each speaker system is correct, and
the speaker devices are mechanically aligned accord-
ing to the manufacturer’s recommendations.
Remember that equalizers are used to tune the room,
NOT to correct poor speaker installation and align-
ment.
SUB-BASS LEVELS:
With the Pink Noise Generator Card plugged into the
Matrix Card slot, turn on the LEFT and RIGHT pink
noise switches. Turn off the Left and Right channel
amplifiers to prevent sound from the Left and Right
stage speakers from affecting this adjustment. Adjust
the SUB LEVEL trimpot on the Output Card for 90
dBC spl from the subwoofer. The installer may wish to
adjust for another level, depending on the amount of
subwoofer desired. Turn the Left and Right channel
amplifiers back on.
An alternative procedure is to turn on the LEFT and
RIGHT pink noise switches and adjust the SUB LEVEL
on the Output Card to “level out” the lower end fre-
quencies as viewed on an RTA set up in the auditori-
um. Do not turn off the Left and Right channel ampli-
fiers for the alternative method.
Plug the MATRIX Card back into its slot.
OPTIONAL 3-D MONO FUNCTION:
No adjustments are necessary for units equipped with
the optional 3-D Mono/Backup Card.
MUSIC LEVELS:
Set the MUSIC LEVEL control, located behind the
front panel on the right side of the Format Card, two-
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.
10
5
0
-5
-10
-15
31.5
63
125
250
500
1K
2K
4K
8K
16K
Diagram 3
dB
The optional 1/3 octave EQ card
