OPTIMOD SURROUND PROCESSOR OPERATION
3-53
A typical setting of the Bass>LFE BASS COUPLING control is 3 dB, which caps the pos-
sible dynamic LFE boost at 3 dB. Some may prefer 0 dB, which precludes any dynamic
LFE boost.
2B Master Attack
sets the attack time of the Two-Band Compressor master com-
pressor (above 200Hz).
2B Bass Attack
sets the attack time of the Two-Band Compressor bass compressor
(below 200Hz).
2B Master Comp Ratio
and 2B Bass Comp Ratio set the compression ratio of the
Master compressor and Bass compressor respectively at their thresholds of compres-
sion. Beyond threshold, the ratio increases with increased gain reduction until it be-
comes ∞:1 at the amount of gain reduction (in dB) set by the 2B
MASTER KNEE con-
trol. When you adjust these controls, the thresholds of the multiband compressors
change automatically so that the total amount of gain reduction stays approxi-
mately the same. (This automatic adjustment is internal to the 8685’s DSP; the MB
THRESH controls’ displayed settings do not show it.)
To achieve a classic soft knee characteristic, set the 2B
MASTER COMP RATIO control to
1:1 and set the K
NEE control to the gain reduction in dB at which you wish the com-
pression ratio to level off to ∞:1. The maximum setting produces the softest knee.
Setting the K
NEE to 0 dB produces a classic hard knee curve with ∞:1 compression ra-
tio regardless of the setting of the 2B
MASTER COMP RAT IO control.
See Figure 3-2 on page 3-54 for the curves of output level vs. input level for various
settings of the K
NEE and RATIO controls.
2B Knee
(see 2B MASTER COMP RAT IO above).
2B Breakpoint
The release rate (measured in dB/second) in the 8685’s compressors
is constant when the gain reduction is higher than the control’s setting, and expo-
nential when the gain reduction is lower than the control’s setting.
When the release is exponential, the release rate is proportional to the amount of
gain reduction. Do not confuse this with the reverse exponential characteristic trig-
gered by setting the 2B
RELEASE SHAPE control to EXPONENTIAL. In this case, release
commences slowly and then speeds up as it progresses.
The 2B
BREAKPOINT control is only active when the 2B RELEASE SHAPE control is set to
L
INEAR.
Compression-induced audio density remains constant when the gain reduction is
above the 2B
BREAKPOINT setting. When the gain reduction is below the 2B
BREAKPOINT setting, density decreases proportionally to the amount of gain reduc-
tion.
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