Yamaha mLAN Mixer Owner's Manual page 32

EXPAND
An expander is similar to a compressor except that it works on signals below the threshold level. By
reducing signals below the threshold level, the expander attenuates low-level noise, effectively increasing
the dynamic range and improving the signal-to-noise performance. An expander set to an infinite ratio
(i.e., :1) is essentially a gate. The following two graphs show typical expander curves. The one on the
left shows an expander with an expansion ratio of 2:1 and a hard knee setting. The one on the right
shows an expander with an expansion ratio of 2:1 and a soft knee setting of 5.
+20
Expansion ratio = 2:1
+10
0
Knee = hard
–10
–20
–30
–40
–50
–60
–70
–70 –60 –50 –40
Parameter
THRESHOLD
–54 dB to 0 dB (55 steps)
OUT GAIN
0.0 dB to +18.0 dB (0.5 dB steps)
KNEE
hard, 1, 2, 3, 4, 5
ATTACK
0–120 ms (1 ms steps)
5 ms–42.3 s (fs = 48 kHz)
RELEASE
6 ms–46 s (fs = 44.1 kHz)
RATIO
1:1, 1.1:1, 1.3:1, 1.5:1, 1.7:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 5:1, 6:1, 8:1, 10:1, 20:1,
THRESHOLD
—This determines the level of input signal required to trigger the expander. Signals above
the threshold pass through the expander unaffected. Signals at and below the threshold level are attenuated
by the amount specified using the Ratio parameter. The trigger signal is sourced using the KEY IN parameter.
OUT GAIN
—This sets the expander's output signal level, and can be used to compensate for the over-
all level change caused by the expansion process.
KNEE
—This determines how expansion is applied at the threshold point. When set to hard, expansion
at the specified ratio is applied as soon as the input signal level falls below the specified threshold. For
knee settings from 1 to 5, however, expansion is applied gradually as the signal falls below the specified
threshold, creating a more natural sound.
ATTACK
—This determines how soon the signal is expanded once the expander has been triggered.
With a fast attack time, the signal is expanded almost immediately. With a slow attack time, however,
the initial transient of a sound passes through unaffected. Attack times from 1 to 5 milliseconds are a
good place to start.
RELEASE
—This determines how soon the expander returns to its normal gain once the trigger signal
level exceeds the threshold. If the release time is too short, the gain will recover too quickly causing level
pumping (i.e., noticeable gain fluctuations). If it is set too long, the expander may not have time to
recover before the next low-level signal appears, and it will be expanded incorrectly. Release times from
0.1 to 0.5 seconds are a good place to start.
RATIO
—This determines the amount of expansion. That is, the change in output signal level relative
to change in input signal level. For a 2:1 ratio, for example, a 5 dB change in input level (below the
threshold) results in a 10 dB change in output level. For a 5:1 ratio, a 2 dB change in input level (below
the threshold) results in a 10 dB change in output level.
Threshold = –10dB
–30 –20 –10 0 +10 +20
Input Level (dB)
+20
Expansion ratio = 2:1
+10
Knee = 5
0
–10
–20
–30
–40
–50
–60
–70
–70 –60 –50 –40
Range
32
Threshold = –20dB
–30 –20 –10 0 +10 +20
Input Level (dB)
:1 (16 steps)