Lexicon 300L - REV Owner's Manual page 70

SPR works together with SHP to control the duration of the initial ambience
created by the 300L. Low SPR settings result in a rapid onset of reverberation
at the beginning of the envelope, with little or no sustain. Higher settings spread
out both the buildup and sustain.
As SHP is advanced, reverberation builds up more slowly and sustains for the
time set by SPR. With SHP in the middle, the buildup and sustain of the
reverberation envelope emulates a large concert hall (assuming that SPR is at
least halfway up, and that SIZ is suitably large—30 meters or larger.)
SIZ sets the rate of buildup of diffusion after the initial period (which is controlled
by DIF). It also acts as a master control for RTM and SPR. The SIZ control
changes a reverb sound from very large to very small. Generally, you should set
the SIZ control to approximate the size of the acoustic space you are trying to
create, before adjusting anything else. The size in meters is roughly equal to the
longest dimension of the space. Moving SIZ while a signal is present may cause
audible transients on critical material.
The apparent size of the space created is actually a combination of the settings
of the SIZ, SHP, and SPR controls. Small acoustic spaces are characterized by
a rapid buildup of diffusion. However, both small and large spaces frequently
have an uneven buildup of initial reverberation. This uneven buildup is controlled
by the SPR and SHP controls.
HFC sets the frequency above which a 6 dB/octave low-pass filter attenuates the
processed signal. It attenuates both pre-echoes and reverberant sound. High
frequencies are often rolled off with this parameter, resulting in more natural
sounding reverberation. HFC is typically set betwen 2kHz and 6kHz.
PDLY adjusts an additional time delay between the input of signal and the onset
of reverberation. The control is not intended to mimic the time delays in natural
spaces. In real rooms the build-up of reverberation is gradual, and the initial time
gap is usually relatively short. Natural spaces are best emulated by setting SHP
at a middle value and adjusting SPR for the desired effective initial reverb
envelope.
Additional delay added with the PDLY control can increase the initial time gap
slightly, emulating a situation where reverberant pick-up microphones are
located much further from the source than the main microphones. If more than
about 30ms of pre-delay is added, this additional delay can add clarity with some
music, but it can also sound unnatural. Large pre-delays can be useful for slap-
echo effects.
* A quick "double-click" on the slider button will allow you to control this delay with
more resolution. To exit this "fine control" mode, double-click on the button
again.
The Algorithms and their Parameters
SPR (Spread)
SIZ (Size)
HFC (High Frequency Cut)
PDLY (Predelay)*
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