Lexicon 300L -, Owner'S Manual

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4-7
The Algorithms and their Parameters
SHLF modifies the low-pass characteristic of the rolloff control, turning it into a
shelving filter. SHL sets the gain of an output path which is mixed with the output
of HFC to form the main reverberant output. Both the pre-echoes and the
reverberation are affected. For example, if SHLF is set to -6dB, frequencies
below approximately HFC/2 will be boosted by 3.5dB; above approximately HFC
x 2, the response will be flat.
SHLF provides a method for making the spectral content of the reverberation
match the ideal spectrum for musical acoustics in rooms. For this application,
HFC should be set between 700 and 1.5kHz, with SHLF set between -12 and
-6dB.
A note about Pre-Echoes
Pages Four and Five contain four pre-echo taps with delay and level controls.
The taps are fed directly to the output wet signal rather than into the reverberator.
Pre-echoes can best be understood by visualizing a stage where the early
reflections are the sounds emanating from the rear and side stage walls directly
after the sound from the stage. Usually the rear stage wall reflection is earlier and
louder than those from the two side walls. The pre-echoes are actually clusters
of echoes, with the density of the cluster set by DIF.
The pre-echo delay parameters change the perceived locations of reflecting
surfaces surrounding the source. Level adjusts the loudness of the reflection.
For each of the LV (Pre-echo level) parameters, there is a corresponding DL
(pre-echo delay) parameter. Each of these sets the delay time in ms for one of
the pre-echoes. These are not affected by PDLY, so pre-echoes can be placed
to occur before or after the reverberation starts.
Random Hall Page Four
The DL pre-echo delay parameters have a resolution of 2 milliseconds.
The LV pre-echo level parameters have sixteen steps, calibrated in decibels.
The FB feedback parameters (for Delays 3 and 4 only) are adjustable in 6%
increments from -93% to +93%.
Pre-Echo 1, one second maximum to left channel.
Pre-Echo 2, one second maximum to right channel.
* A quick "double-click" on the DL1 or DL2 slider button will allow you to control
the delay with more resolution. To exit this fine control mode, double-click on the
button again.
RTM sets the reverb time for mid-frequency signals. Because low-frequency
reverb time (BAS) is a multiplier of RTM, RTM acts as a master control for the
reverb time.
SHLF
DL1*, LV1
DL2*, LV2
RTM (Mid-Frequency
Reverb Time)