Lexicon MPX 500 User's Manual

Reverb
Parameters

Adjust

Decay

HF Rlloff
MIX

PreDelay

BassMult

BassXvr

Rt HC

Diffusion

Size

Attack

Level

MPX 500 Parameter Descriptions

Adjust is a "magic" control whose function is different from preset to
preset. It usually controls several parameters but may also provide a set
of special values for a single control, for example "Fast" and "Slow" for a
parameter that is also adjustable to any value via another control.
Adjust has a range of 0 to 127 so as to provide a convenient attachment
point for a MIDI controller.
Decay controls reverb time for mid frequency signals. In Ambience,
Decay controls the length of the ambience "tail".
Sets the high frequency cutoff of a post-effect low-pass filter.
MIX controls the ratio of direct (“Dry”) vs. effect (“Wet”) signal in the
output. When the MPX500 is patched into a console, this control should
almost always be set to “Wet” (i.e. 100%).
Controls the time delay between the input of signal and the onset of
reverberation.
BassMult (called “Bass Multiply”) controls the reverb time for low­frequency signals; it works as a multiplier of the Decay (a.k.a. MidRT)
parameter. For example, if BassMult is set to 2x, and Decay is set to two
seconds, the low frequency reverb time will be four seconds. For a
natural-sounding hall ambience, BassMult should usually be between 1x
and 2x.
BassXvr (called “Bass CrossOver”) sets the frequency below which
BassMult applies.
Rt HC (usually called “Reverb Time Hi Cut”) sets the frequency above
which high frequencies are rolled off in the reverberated signal. This
causes reverberated signals to grow progressively darker and results in
more natural-sound because it simulates the effect of air absorption in a
real hall. Setting a low frequency for this parameter can actually shorten
the reverb time because it dampens the audio as it re-circulates.
Diffusion controls the degree to which initial echo density increases over
time. High settings of Diffusion result in high initial buildup of echo
density. (Echo density is also affected by Size, with smaller spaces
sounding denser.)
Size sets the rate of buildup of echo density after the initial period (which
is controlled by Diffusion). It also acts as a master control for Decay.
Size changes a reverb sound from very small to very large. Generally,
you should set the Size control to approximate the size of the acoustic
space you are trying to create before you adjust anything else. The size
in meters is roughly equal to the longest dimension of the space.
(Adjusting Size causes the program to re-load.)
Attack controls the sharpness of the initial response to an input signal.
High settings cause an explosive sound, while low settings cause the
sound to build up more slowly with time. Attack affects the level of sound
within only the first 50 milliseconds or so.
Level determines the amount of wet signal present in the output. It
functions similarly to Mix control except that it affects the Wet
component only. It is generally used to balance the overall output of two

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EkoDly L, EkoDly R

EkoFbk L, EkoFbk R

Inverse
Parameters

Duration

LowSlope,
HighSlope

Shape

Spread

MPX 500 Parameter Descriptions

or more programs when Mix is set to Wet.
In the reverb (Plate, Hall, Chamber, etc.) programs, these parameters,
called Delay Level Left and Delay Level Right, control the timing of
single reflections that occur early in the decay. These reflections
simulate the sound you might hear off of the back wall of a stage or
other reflective surface.
In the reverb programs, these parameters, called Echo Feedback Left
and Echo Feedback Right, control the amount of repeating echo that
simulates a flutter echo between parallel walls. The range of these
parameters is from -100% to 100%, with negative values producing a
polarity reversal. High values can cause signal overload.

This determines the length of time, in milliseconds, which passes before
the cutoff of output occurs.
These parameters are found only in the Inverse programs. LowSlope
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. 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.
HighSlope is similar to LowSlope, but applies to middle and high
frequencies.
Similar to Attack in the reverbs, it controls the buildup of those early
reflections, which most audibly create the sound of a real room.
Along with Size, this controls the timing between the initial reflections,
which most audibly create the sound of a real room. Shape and Spread
work together; if either is set to 0, the other has no effect.

Ambience
Parameters

Rvb Lvl

Tremolo
Parameters

Phase
Rate
Depth
Waveform

Rotary
Parameters

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In Ambience, short-decay early reflections create a real-room sound.
Rvb Lvl controls the amount of “extra” longer-decay reverb added to this
effect.

Phase determines the relative timing between the L and R channels.
Rate controls the speed of volume modulation.
Depth controls how much the volume is modulated.
Waveform determines how the volume is modulated with time. Values
are Sine (smooth modulation with polarity reversal), Rectified Sine
(smooth modulation with no polarity reversal), Triangle (linear ramp up
and down), Sawtooth (linear ramp up with sudden reduction), and
Square (level switches between maximum and minimum).

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