Installer’s Guide
34
Set Up the Main Voice EQ
The
VGM-1041’s
seven-band parametric
Main Voice EQ
is where you tune your
entire sound system – residual mic responses, speakers, and room acoustics – to provide the
best sound. Often, “best sound” translates to,
gain before feedback
. The higher your
operators can turn up a mic without problems, the easier it will be for them to give the
audience the sound they deserve. Please see the
gain before feedback
discussion on pages
10 -- 11. Typically as a mic is turned up, overall response rises until its highest peak reaches
the point where feedback becomes objectionable – it shows up first as
ringing
-- an annoying
echo at the problem frequency. Turning it even higher yields the familiar “howl”. If we
adjust the EQ to attenuate sound at this peak, we get more room to turn up the mic – we
achieved this much more gain before feedback. Thus, by leveling the peaks and valleys of
your system’s overall response, you’ll also achieve the best gain before feedback.
By-Ear Method
This method takes
advantage of the effect
described above to
locate your response
peaks. Basically, you
increase a mic’s gain
until you begin to hear
feedback. For example,
it’s evident that the
peak (or
feedback
node
) labeled
1
here,
will sound off
first
as
gain is increased.
We then tune one of the EQ filters to flatten the peak that caused this feedback. This allows
you to turn up the mic further, in turn discovering the next feedback node. Continue this
process until the system tends toward feedback at several competing feedback nodes – this
indicates you’ve reached diminishing returns. Some helpful tips:
•
Perform this procedure
on
your “main” mic
, the one used the most
•
Temporarily
set this mic channel’s options
(see page 28):
o
Disable gating
, switch
De-Ess OFF
, and
Compression ON
.
•
Station an assistant
at this mic as if using it. Often their very presence affects the
mic’s acoustics. Occasionally have them speak (reading a book works well).
•
Increase
the mic’s control until you hear ringing. If you can’t get feedback with the
control advanced, use the
T
hotkey (see page 26) to obtain more gain.
•
To
find
the feedback node
frequency
:
o
Set a filter for narrow bandwidth and about -6 dB gain, then use the
U
p &
D
own keys to
sweep
the frequency
until the feedback goes away.
o
Or, use a Real-Time Analyzer (RTA) Smartphone app to identify the node.