Lexicon 300L - REV 1 Owner's Manual page 92

Chamber Page One
RTM sets the reverb time for mid-frequency signals. Because BAS is a multiplier
of RTM, RTM acts as a master control for the reverb time.
BAS sets the reverb time for low-frequency signals, as a multiplier of the RTM
parameter. For example, if BAS is set to 2x, and RTM is set to two seconds, the
low frequency reverb time will be four seconds. For a natural-sounding hall
ambience, we recommend values of 1.2x or less.
XOV sets the frequency at which the transition from RTM to BAS takes place.
XOV should be set at least two octaves higher than the low frequency you want
to boost. For example, to boost a signal at 100 Hz, set XOV to 400 Hz (This
setting works well for classical music). XOV works best around 400 for boosting
low frequencies, and around 1.5 kHz for cutting low frequencies.
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.
TDC sets the frequency above which sounds decay at a progressively faster
rate. When set relatively low, it gives a darker tone to the reverberation,
simulating the effect of air absorption in a real hall. TDC also helps keep the
ambience generated by the program from muddying the direct sound.
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 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
The Algorithms and their Parameters
RTM (Mid-Frequency
Reverb Time)
BAS (Bass Multiply)
XOV (Bass Crossover)
SIZ (Size)
TDC (Reverb Treble Cutoff)
PDLY* (Pre-Delay)
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