PRESONUS StudioLive24.4.2 - Page 131

PreSonus StudioLive
™
24.4.2
130
Quick Start:
Level
Setting
Overview Controls Connecting
to a
Computer
Scenes,
Presets &
System
Menu
Technical
Information
Trouble-
shooting
& Warranty
Tutorials
8 Tutorials Owner’s Manual
131
Quick Start:
Level
Setting
OverviewControlsScenes,
Presets &
System
Menu
Technical
Information
Trouble-
shooting
& Warranty
Tutorials
Tutorials 8
Software
Universal Control,
Capture, and
Studio One Artist
Hookup
Hookup
Software
Universal Control,
Capture, and
Studio One Artist
Connecting
to a
Computer
A Brief Tutorial on Dynamics Processing 8.28.2 A Brief Tutorial on Dynamics Processing
Why do the best consoles in the world put compressors on every channel?
The answer is simply that most instruments need some form of
compression, often very subtle, to be properly heard in a mix.
Why do we need noise gates?
Consider the compressed vocal example discussed earlier; you now have a
20 dB dynamic range for the vocal channel. Problems arise when noise or
instruments (air conditioner, loud drummer, etc.) in the background of the
vocal mic become more audible after the lower end of the dynamic range is
raised. You might attempt to mute the vocal between phrases in an attempt to
remove the unwanted sounds; however, this would probably end disastrously.
A better method is to use a noise gate. The noise-gate threshold could be
set at the bottom of the dynamic range of the vocal, say -10 dBu, such that
the gate would shut out the unwanted signals between the phrases.
If you have ever mixed live sound, you know the problems cymbals can create
by bleeding through the tom mics. As soon as you add some highs to get some
snap out of the tom, the cymbals come crashing through, placing the horn drivers
into a small orbit. Gating those tom mics so that the cymbals no longer ring
through them will give you an enormous boost in cleaning up the overall mix.
Dynamics processing is the process of altering the dynamic range
of a signal, thereby enhancing the ability of a live sound system
or recording device to handle the signal without distortion or
noise and aiding in placing the signal in the overall mix.
8.2.2 Types of Dynamic Processing
Compression/Limiting
Punch, apparent loudness, presence—these are just three of the many
terms used to describe the eects of compression/limiting.
Compression and limiting are forms of dynamic-range (gain) control. Audio
signals have very wide peak-to-average signal-level ratios (sometimes
referred to as dynamic range, which is the dierence between the loudest
level and the softest level). The peak signal can cause overload in the audio-
recording or sound-reinforcement chain, resulting in signal distortion.
A compressor/limiter is a type of amplier in which gain is dependent on the
signal level passing through it. You can set the maximum level a compressor/
limiter allows to pass through, thereby causing automatic gain reduction
above some predetermined signal level, or threshold. Compression refers,
basically, to the ability to reduce, by a xed ratio, the amount by which a
signal’s output level can increase relative to the input level. It is useful for
lowering the dynamic range of an instrument or vocal, making it easier to
record without distorting the recorder. It also assists in the mixing process by
reducing the amount of level changes needed for a particular instrument.
Take, for example, a vocalist who moves around in front of the microphone while
performing, making the output level vary up and down unnaturally. A compressor
can be applied to the signal to help correct this recording problem by reducing
the louder passages enough to be compatible with the overall performance.
How severely the compressor reduces the signal is determined by the compression
ratio and compression threshold. A ratio of 2:1 or less is considered mild
compression, reducing the output by a factor of two for signals that exceed
the compression threshold. Ratios above 10:1 are considered hard limiting.
As the compression threshold is lowered, more of the input signal is
compressed (assuming a nominal input-signal level). Care must be taken
not to overcompress a signal, as too much compression destroys the
acoustic dynamic response of a performance. (That said, overcompression
is used by some engineers as an eect, with killer results!)
Limiting refers to the processing that prevents the signal from getting any
louder (that is, it prevents any increase in the signal’s amplitude) at the output.
Compressor/limiters are commonly used for many audio applications. For example:
A kick drum can get lost in a wall of electric guitars. No matter how
much the level is increased, the kick drum stays lost in the “mud.” A
touch of compression can tighten up that kick-drum sound, allowing
it to punch through without having to crank the level way up.
A vocal performance usually has a wide dynamic range. Transients (normally
the loudest portions of the signal) can be far outside the average level of the
vocal signal. Because the level can change continuously and dramatically, it is
extremely dicult to ride the level with a console fader. A compressor/limiter
automatically controls gain without altering the subtleties of the performance.
A solo guitar can seem to be masked by the rhythm guitars. Compression can
make your lead soar above the track without shoving the fader through the roof.
Bass guitar can be dicult to record. A consistent level with good attack
can be achieved with proper compression. Your bass doesn’t have to
be washed out in the low end of the mix. Let the compressor/limiter
give your bass the punch it needs to drive the bottom of the mix.
Compressors — Terminology
Threshold. The compressor threshold sets the level at which compression begins.
When the signal is above the threshold setting, it becomes eligible for compression.
Basically, as you turn the threshold knob counterclockwise, more of the input
signal becomes compressed (assuming you have a ratio setting greater than 1:1).
Ratio. The ratio is the relationship between the output level and the input level.
In other words, the ratio sets the compression slope. For example, if you have the
ratio set to 2:1, any signal levels above the threshold setting will be compressed
such that for every 1 dB of level increase into the compressor, the output will
only increase 0.5 dB. This produces a compression gain reduction of 0.5 dB/
dB. As you increase the ratio, the compressor gradually becomes a limiter.