Orban 622B - 2: Sound Reinforcement

2:
SOUND
The
622 is a
versatile
sound
reinforcement
equalizer which can
function as
a
notch
filter and
broadband
equalizer.
Man/
reinforcement
systems
are mono.
In these
installations,
particularly
powerful
results
can be
obtained by
connecting
both
622B channels in
series .
A
total of
eight bands
are
then
available for
notch
filtering or
equalization.
House
Tuning:
In an
economy
installation,
the
622B (with
both channels
connected
in series)
can do a
surprisingly
effective
job of
tuning a
reinforcement
system to a
room
without the use of a
third-octave
filter set. Use
three or
four of
the bands
in their
narrowband
notching
mode
(BANDWIDTH full
counterclockwise)
to
notch
out
the major
ring modes.
This
is
most
effectively and
safely
done
if
there is a
limiter or
compressor
in the
circuit
before the
power
amplifier to
prevent
speaker
damage.
Advance
system
gain until
it feeds
back
at
a single
frequency. Make
sure
that
the limiter is
in
gain reduction
to
protect the
speakers.
Estimate the
frequency of
the
feedback, and
choose
a
band on the
622
which covers
it.
Turn the
BANDWIDTH control to
broad
,
and
turn the
EQ control
down to
-infinity.
Adjust
the
TUNING
control until
the
feedback
changes
frequency.
Continue
to adjust
the
TUNING control
until
the feedback
returns at
its
original
frequency.
Set the
TUNING control
half-way
between
the two
settings
where the
feedback
was
observed
to change
frequency.
Now reduce
the
BANDWIDTH to full CCW
(narrowband), and
readjust
the
TUNING
as
necessary
to keep
the
notch centered
on
the ring
frequency.
Finally, turn the
EQ control
up
toward
"0"
(or flat)
until
the
ring
frequency
reappears.
Back
off about
4dB, This will
leave
headroom so
that
the
ring
frequency
will
not
reappear
when the
system
gain is
increased
when
more ring
modes
are
tuned
out
later.
This
procedure
may be
repeated
with
the
new ring
frequencies
as
they
appear.
Usually
after the
first
four ring
frequencies
have been
eliminated,
the
"point
of
diminishing
returns"
is
reached.
The
remaining
bands
on the
622B are
now
available to
perform
broadband
equalization of
the
system.
Use a
pink-noise
generator and
third-octave
real-time
analyzer
for
most
precise
results.
However,
if your
budget
doesn't
permit a
third-
octave
analyzer,
use
your
ears.
Fortunately,
you only
have
four or
five
bands to
deal
with
—
not
a
whole
third-octave
set!
Notch
Filtering:
If
a
third-octave
filter set
is
available
for
broadband
equalization,
the
622B
may be
used
solely as a
narrowband
notch
filter
set to
eliminate
up to
eight ring
modes.
The notches
obtainable are
somewhat
sharper
than those
created
by
a
third-octave
equalizer.
Stage
Monitors:
The
622 is an
effective
stage
monitor
equalizer
because of
its
low cost
per
channel
and
notching
capabilities.
Follow
the
instructions
in
House
Tuning
above.
Individual
Driver
Equalizer:
Some
practitioners
have
discovered that
there
are
substantial
advantages
to
equalizing
each
driver
in a
complex
sound
reinforcement
system
with its
own
parametric
equalizer.
It is
claimed
that this
is the
best way
to
correct
for
individual
driver
response
anomalies
without
having
the
corrective
equalization
affect
other
drivers.
9