Manual

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2.4.2 General Limiter Operation
There are many methods and approaches to programme limiting that are favoured amongst
users. In general however, these fall into the two main categories described below.
The least intrusive kind of limiting is achieved with a fast attack and a relatively slow release,
adjusted to suit the general timing of the music. Very long decays, often favoured in classical
music productions, can be achieved with the Oxford limiter by using a combination of both
release and hold times. Due to the look-ahead processing, the Oxford limiter also has a
significant range of attack time that can be used without peak level overshoot. This means
that a slower and gentler limiting can be achieved during the onset of loud passages within
the programme material, without breaching maximum level, as set by the threshold control.
2.4.3 Maximising Loudness with the Limiter
A recent popular use of programme limiting aims to maximise the relative loudness and
average modulation of music by reducing the short-term peak levels within the programme
waveform. This makes it possible to increase the overall volume (gain) of a piece without
getting obvious overloads (red lights) on the final mastered work. The success of this method
depends on the amount of peak reduction that can be obtained without objectionable loss of
quality to the programme. Maintaining the quality of the peaks, without reproducing their
maximum levels, relies on a degree of ‘peak remodelling’.
The basic approach to this function is to initially set attack, hold and release controls to
minimum, for fastest possible action. Then reduce the threshold control to progressively
reduce the gain of the programme, only during the very short periods where peaks occur. The
sound of the peaks can then be adjusted by increasing the attack period to soften the edges
such that a degree of realism is retained, despite the reduction of instantaneous levels during
that period. Since the Oxford limiter has a fairly large look-ahead period, it is possible to
increase the attack time significantly without allowing the peak levels to pass. It is therefore
possible to re-model the limited peaks considerably in real time, retaining good programme
realism despite large degrees of peak reduction. If it is necessary to increase recovery times
after peaks, for instance due to LF modulation content, it is better to use the hold control for
this purpose, as the recovery time is faster for a given overall period than by increasing the
release time. The programme level can then be increased so that the new peaks just reach
maximum level again. Depending on the material, average programme modulation may be
increased by 6dBr or more by using this method.