Symetrix 565E - Paging with Ducking; Feedback Elimination in P.A. Systems and Stage Monitors

565E
17
Paging with Ducking
Many situations involving a “talking host” and any sort of musical background will require the
background music to drop in level whenever the host signal is present. By splitting the host signal,
part of it can be used to tell the 565E when to take action and lower the background source by an
amount determined by the threshold control.
q Set the compressor threshold so that all the gain reduction LEDs for the compressor are
illuminated when the host speaks. Although the display won’t show it, you can set the threshold
control even lower for more ducking action.
q Use the release control to vary the speed at which the music returns when the host stops
talking.
Feedback Elimination in P.A. Systems and Stage Monitors
Public address and sound reinforcement situations that require comp/limiting are often plagued by
feedback problems. The overall increase in level that results from compression can cause feedback
in the absence of signal, when the compressor releases and brings levels back up to normal.
q Set the compressor threshold for no more than 9 dB of gain reduction on normal signals.
q Set the expander threshold for 16 dB (or more) of gain reduction when the signal source is
silent, and 0 dB of gain reduction when the signal is present.
q Use the release control to make the expander follow momentary pauses.
q Since the successful implementation of this technique requires careful setting of the two
threshold controls, be prepared to fine tune the settings to match the levels of your system and the
vocalist’s style.
CH1 OUTPUT
-10 0dBu CLIP
CH1 LIMITER
-12 -6 -9 -3
-20 -4 -6 -2 -15 -10 -12 -8 -25
CH1 COMPRESSOR
CH1 EXPANDER
-18 -2 -12 -6
IN
+5 0
+10-10-3 +13
BYPASS
4-10
62.5+5
+20
-20-12
BYPASS
THRESHOLD (dBu) GAIN (dB)
10
1
RATIO (X:1)
FAST-40
+20 SLOW
RELEASE
-12
-25 0
565
DUAL
EXPANDER
COMPRESSOR/
LIMITER/
E
SLOW
BYPASS
FAST
RELEASE
+10
THRESHOLD (dBu) THRESHOLD (dBu)
-25
S
INPUT
AUDIO
INPUT
TO LINE
OUTPUT
TO MIC
INPUT
P
MA
PRE-AMP
MICROPHONE
PAGE
MIC
SPLITTER
KEY INPUT
TO SIDECHAIN FROM AUDIO
-6 -2 -4 -10 -8 -15 -12 -25
CH1 COMPRESSOR
CH1 EXPANDER
-2 -6 -18 -12
5-10
73+5
10
1
RATIO (X:1)
FAST-40
+20 SLOW
RELEASE
-12
-25 0
SLOW
BYPASS
FAST
RELEASE
+10
THRESHOLD (dBu) THRESHOLD (dBu)
-25