Technical information

APPENDIX 12
Dynamic EQ/Signal Enhancement
Continuing with the notion of the ML4 as an EQ, consider the possibilities of
the multi-band expander. The expander in the ML4 can decrease or increase
signal levels once they drop below a selected threshold. By using the multi-
band expander, a dynamic EQ can be created.
For example, a breathy vocal sound could be realized by boosting low levels in
the high-frequency bands. Or a consistent bottom end can be achieved with a
kick drum or bass guitar by increasing low levels of the lower frequency bands.
Such techniques also highlight why there is a multi-band gate in the ML4:
When low-level signals are boosted, some noise  oor increase can occur. So
the gate threshold can be placed at some level below the expander threshold
level to reduce or remove unwanted signal.
Noise Reduction Using the Gate and Expander
Often the desired signal content is contained in predominantly one or two
bands of the four bands in the ML4. This can be observed from the X OVER
page in the metering section of the ML4 user interface, by selecting the IN
or OUT dynamic plot modes. The crossover frequencies can be adjusted so
a minimum number of bands contain the desired signal (dialog in the  eld),
and the remaining bands have only background noise. Now the Gate and/or
Expander can be used to reduce signal levels in these bands once they fall
below a selected threshold. The Expander in the desired signal band can be
used to increase signal levels for occasional dropouts (for example, an actor
moves o the mic axis brie y). The Compressor in the desired signal band can
control signal peak levels and obtain a relatively constant output level.
Multi-band Gating of Close Proximity Instruments
The multi-band Gate in the ML4 can be used to remove background noise from
instruments in close proximity to each other. A good example of this is the
typical drum kit. The kick, snare, hi-hat, toms, and so on are all usually mic’ed
separately, but signal from adjacent drums elements ‘leak’ into each other’s
tracks. A single-band gate is often used to only ‘open’ a track when signal
from the desired drum element is actually being played. However, many drum
elements have overlapping frequencies, and so the use of a multi-band gate
can readily solve many problems previously unmanageable. The kick drum can
have a less sensitive gate in the low bands (lower threshold) and the other
bands can be more sensitive (higher threshold) can block out background
noise that would have been otherwise impossible to remove.