AirTools 6200 - Dynamics Processing Modules

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6200 Digital Broadcast Delay
Shelving Frequency - Determines where the boost or cut takes place.
For low shelf filters, all frequencies below this will be affected. For
high shelf filters, all frequencies above this will be affected. Technically,
the indicated frequency is the point where the filter has reached half
of its specified dB gain. For example, for +6 dB boost with a 1 kHz
frequency,thesignalisboostedby+3dBat1kHz.
Shelving Gain - Determines the amount of boost or cut applied.
Shelving Type - Defines the type of shelving filter in use (Low Shelf or
HighShelf)andtheaggressivenessoftheshelframp(Gentle,Normal
or Aggressive).
EXPANDER:
An expander reduces the gain of lower level signals thereby increasing
the total dynamic range. Above a user defined threshold setting, signal
levels remain unchanged. Below threshold, signals are reduced by
some degree. An expander reduces the level gradually for decreasing
input level. An expander can be used to reduce room noise during
pauses in speech or reduce noise floor during pauses in program.
Controls:
Bypass/Enabled - When bypassed, the input is sent unmodified to the
output. When enabled, the module processes the signal.
Expander Threshold - The level that the signal must exceed to open the
expander (let it pass signal).
Expander Ratio - The slope of the gain curve below the threshold point.
A high ratio setting begins to approximate the action of a gate.
GainReduction(Meter)-Againreductionmeterisprovidedsothat
the effect of the expander can be observed (present on Threshold and
Ratio menus).
Expander Attack - The duration of the input signal, over threshold,
required to open the expander. Faster attack times let shorter transients
open the expander.
Expander Release - The amount of time required for the gain to return
to the below-threshold value after the input signal falls below threshold.
COMPRESSOR:
A compressor reduces the dynamic range of signals above a user
determined threshold. Signal levels below the threshold remain
unchanged. A compressor can be used to tame transient spikes in
audio sources as well as reducing dynamic range to control wildly
varying levels while increasing intelligibility.
Controls:
Bypass/Enabled - When bypassed, the input is sent unmodified to the
output. When enabled, the module processes the signal.
Compressor Sidechain - Determines the mode of the compressor
module (Compressor or AGC). Certain controls are only applicable
within specific modes.
Compressor Threshold - The signal level above which the compressor
begins reducing the gain. Visually, the point at the knee (bend) in the
input/output curve. For peak stopping, set the threshold just below the
peak level that you want to stop. For dynamic range reduction, pick a
threshold setting that results in a few dB of gain reduction indication
with the signal levels that you are interested in.
Compressor Ratio - The ratio determines the degree of output
change for an above threshold change in the input. Generally ratios
under 10:1 are considered compression while those above 10:1 are
considered limiting.
GainReduction(Meter)-Againreductionmeterisprovidedsothat
the effect of the compressor can be observed (present on Threshold
and Ratio menus). It indicates the amount of gain reduction that
the compressor is currently applying. This meter is pre-output gain,
meaning changes to compressor output gain do not effect this meter.
Compressor Attack - The speed with which the compressor begins
the gain reduction process. Although your intuition tells you that you
want the fastest possible attack time, your ears will tell you otherwise.
Too fast attack times strip transients of their edges, dulling the
sound. Remember that momentary (brief) clipping is inaudible. Faster
attack times allow shorter transients to initiate gain reduction. On the
other hand, too long attack times can allow short transients to pass
unchanged, which may defeat the purpose that the compressor was
intended for.
Compressor Release - The release time determines the moment-
to-moment gain change in the compressor. Fast release times raise
the subjective level, while slow release times are more useful for
keeping levels under control. Very fast release times can cause audible
distortion, especially with low-frequency content.
Compressor Knee - The knee setting determines the compression
ratio during the transition from linear (below threshold) to compressor
operation. A soft knee makes this change gradually, while a hard knee
makes an abrupt transition. A soft knee curve may require several dB of
gain reduction before the actual compression ratio has reached the set
value. For general compression, use the soft setting. For limiting, use
the hard setting.
CompressorMakeup-Themakeupgaincontrolstheoutputgainofthe
module. If the compressor is reducing the signal level significantly, a
boost in the output gain may be required to maintain perceived volume.
SidechainHighPass-A150,300or600Hzsidechainhighpass
filter can be invoked in order to deter low frequency energy from
triggering expander/compressor action and the resultant unwanted gain
reduction.
Lookahead Delay - A lookahead delay can be enabled which allows the
module to better predict changes to incoming levels and thus provide
better dynamics processing. Enabling this delay results in an extra 2 ms
processing delay.
AGC:
AGC or Automatic Gain Control is a special case of a compressor with
its threshold set at a very low level, moderate to slow attack times,
long release times, and low ratios. It is intended to take signals of
indeterminate levels up to a target level while maintaining program
dynamics.MostAGCsincorporatesomesortofsilencedetection
to prevent the loss of gain reduction during silent periods. This is
the single feature that separates an AGC from a common, ordinary
compressor/limiter.
Use an AGC to remove some of the variation in level from a person who
isn’t trained on microphone control or to take some of the guesswork
out of setting up dynamics control of unfamiliar input sources. When
setting up the AGC, keep the attack and release times conservative
(perhaps 50ms/500ms for voice and 500ms/500ms for music).
When engaging the AGC mode of the Compressor, some controls are
repurposed, removed or replaced:
AGC Detector Thresh - The AGC Detector Threshold, or more
accuratelytheAARM(AutomatedAttackandReleaseMonitor)Detector
Threshold,isafixedthresholdbelowwhichtheAARMcircuitstops
calculating changes in gain. When the input signal level is below the
threshold, the AGC gain/attenuation will be locked, and therefore will
not be changing. Set this threshold to a level 10-20dB above the noise
floor of your input signal. It can be dangerous if the threshold is too
close to the noise floor, as this could cause the noise floor to be raised
in some cases. (Effective in AGC mode only).
Basic Setup