Symetrix 425 - Applications; Removing Noise from Vocal Tracks

8. Applications
Here are a few applications that the 425 lends itself to. The following applications make one
assumption: settings for the threshold control(s) are a function of each individual system's
actual operating level. Wherever specific threshold settings are mentioned, they are referenced
to either a particular gain reduction level as indicated by the meter, or to a O dBu input level.
8.1 Vocal Level Smoothing
This application assumes that the voice source does not vary tremendously in level. Examples
of this include narration, commercial voice-over production, seminar speaking, etc.
2.51.3
THRESHOLD (dBu)
-25 +10
SLOW
FAST
-2
-4 -6 -8
2
10
1
RELEASE RATIO (X:1)
BYPASS
-10
-40
-25 -15 -12 -10
COMPRESSOR
q Lower the threshold setting until the gain reduction display
begins to show compression, then continue lowering the
setting until the display shows 6-9 dB of gain reduction on
peaks.
q To eliminate noises like paper rattling or breathing, try
using the downward expander.
8.2 Removing Noise from Vocal Tracks
Sometimes, due to the more abrupt nature of gating, it may be more appropriate to clean up a
noisy vocal track with a downward expander. The 425's expander is smooth, and can clean up
vocals without cutting into phrasing.
-30 -5
BYPASS
-2 -6 -12 -18
SLOW
FAST
RELEASETHRESHOLD (dBu)
+5
-20
EXPANDER
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 the phrasing.
8.3 Constant Level Paging
All too often, paging announcements are either sub-audible, or distorted. The problem is the
result of changing input levels from different users (timid Tom vs Sam Screamer) and
unpredictable environmental circumstances. To optimize system levels for intelligibility
without overload, use the compressor section to even out levels, and the peak limiter to put a
clamp on Sam Screamer.
q Set the compressor threshold for 6 dB of gain reduction
with normal paging levels.
q Set the peak limiter threshold for 6 dB of gain reduction
when Sam Screamer is on the system.
q All normal signals will be slightly compressed, and really
loud signals will activate the peak limiter. With these
settings a shy person will be audible, and the guy who
thinks he has to shout won't be too loud, or cause
distortion.
2.51.3
THRESHOLD (dBu)
-25 +10
SLOW
FAST
-2
-4 -6 -8
2
10
1
RELEASE RATIO (X:1)
BYPASS
-10
-40
-25 -15 -12 -10
COMPRESSOR
8-1
Rev 2.0, 10/29/93