SPL 9945, User Manual

Page: 13 / 28

13
Operation
Compressor/Limiter
Limit
The Limit button switches the Compressor to limiter mode. The Gain
Reduction control serves the purpose of controlling the threshold. The
Limiter does not function as a peak limiter, in other words there is no
guarantee that all peaks are intercepted. It is therefore advisable when
modulating a subsequent unit that a headroom of 2 to 4 dB remains. Peak
limiters have a system-based disadvantage in that audible distortions are
heard considerably sooner.
Gain Reduction
The Gain Reduction control sets the intensity of compression. Turning the
control clockwise increases compression.The working area spans b
20 dB (counter clockwise limit) and -50 dB (clockwise limit).
The compressor applies the so-called ”soft-knee” characteristic, which
means that quiet passages are processed at a lower compression ratio than
louder passages. At maximal compression it operates with a ratio of 1:2.5 –
very effective dynamic limits are achievable when inconspicuous characteri-
stics are to be processed. The exact development of the compressor curve is
portrayed in the diagram 1 on page 24. When setting the compression rate
the Gain Reduction display in the display field is of great assistance. The
effect on the selected compression rate is scaled in 1.5 dB steps. Depending
on signal source and dynamic structure the reduction values should lie
between 4 and 8 dB to restrict higher peaks and to optimize the operation of
the subsequent recording system.
Noise Gate
The Noise Gate control monitors the noise gate by which soft disturbances
are reduced during signal pauses. When turned fully counter clockwise the
noise gate is switched off. By turning the control in a clockwise direction the
threshold value increases. This means that the Noise Gate closes relatively
earlier.
The processing span of the Noise Gate is between –100 dB (gate control
turned fully counter clockwise) and + 18 dB (gate control turned fully clock-
wise). The Noise Gate is therefore operable over the complete dynamic
range.
With a hysteresis of 6 dB the noise gate functions very stably: the point at
which the Noise Gate opens lies 6 dB above the point at which the Noise
Gate closes again. Definite closure and opening is therefore assured – the
most feared characteristic of ”fluttering” is excluded. Even critical signals are
cleanly processed.
The release-time setting takes place automatically. The automation, which
depends upon the program, adjusts itself to the release time of the musical
piece thereby ensuring optimal (undetectable) opening and closing.