Lexicon PCM 91 - REV - Time Parameters

Lexicon
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PCM 91 User Guide
BassBoost
A positive value for Gain may reduce low frequencies in program material.
Conversely, a negative value for Gain may increase low frequencies. BassBoost
allows compensation for this effect by boosting or cutting frequencies below
Crossover. The amount of boost or cut required is highly dependent on the
material being processed. Start by setting this control to the same value as the
Gain control, and then adjust it as necessary.
The Time row, available in every algorithm, contains parameters that affect the
time-based aspects of the reverb effect.
Low Slope and Mid Slope
These parameters are found in the all of the Inverse Rvb Time rows. Low Slope
determines the shape of the reverb envelope for low frequencies. When set to
0, the level of low reverb remains unchanged over its Duration, then cuts off
abruptly (depending on the amount of diffusion in use). Setting Low Slope above
0 causes the level of low frequency reverb to rise smoothly from soft to loud until
the sound is cut off. The greater the slope, the softer the initial reverberation and
the more pronounced its rise. With negative values, the low frequency reverb
drops from its initial level to a quieter one before cutoff. The lower the slope, the
more pronounced the dropoff. Mid Slope is similar to Low Slope, but applies to
middle and high frequencies. The actual frequencies affected are determined by
Crossover.
Mid Rt and Low Rt
Mid Rt sets the reverb time for mid-frequency signals. Because low frequency
reverb time (Low Rt) is a multiplier of Mid Rt, Mid Rt acts as a master control for
the reverb time.
Low Rt sets the reverb time for low-frequency signals, as a multiplier of the Mid
Rt parameter. For example, if Low Rt is set to 2X, and Mid Rt is set to two
seconds, the low frequency reverb time will be four seconds. For a natural-
sounding hall ambience, we recommend values of 1.5X or less.
Crossover
Crossover sets the frequency at which the transition from Mid Rt to Low Rt takes
place. This control should be set at least two octaves higher than the low
frequency you want to boost. For example, to boost a signal at 100Hz, set
Crossover to 400Hz. (This setting works well for classical music.) Crossover
works best around 400Hz for boosting low frequencies, and around 1.5 kHz for
cutting low frequencies.
Rt HC
Rt HC sets the frequency above which a 6dB/octave low-pass filter attenuates
the reverberated signal. It does not attenuate the reflections. High frequencies
are often rolled off with this parameter, resulting in more natural-sounding
reverberation. Setting a low frequency for this parameter can actually shorten
the reverb time, as it damps the audio as it recirculates.
Time