48
Manual del Usuario
/ DXI series /
User’s Manual
ANNEX I: LIMITERS AND HOW TO SET THEM CORRECTLY (cont'd)
The peak limiter predelays the sidechain signal,
resulting in a “zero overshoot” limiter, which is able to
catch all peaks and provide a reliable absolute
maximum setting for the output of any channel.
The predelayed sidechain is shown in green, with
the main signal in red. As the main signal arrives slightly
after the sidechain, the output from the unit does not
suffer from the overshoot problem.
Remember that this delay is only in the order of tens
of microseconds, and is a pre-delay – the sidechain is
moved back in time in relation to the main signal.
Inserting a delay into the main signal path of an
analogue dynamics processor will achieve similar
results, but with the penalty of delaying the main signal
by the amount of look ahead delay introduced.
Setting Accurate Limiter Thresholds – Program Limiter
The limiters built into your amplifier are intended to be used for loudspeaker driver protection, as opposed
to amplifier protection. The amplifier has additional limiters which can adapt automatically to both temperature
and incoming mains conditions to stay operational and playing music for as long as possible. The following
section describes how to set up the units' limiters to provide exceptional protection against driver overheating
and cone over-excursion. Most speaker systems are given a power rating in Watts RMS. This is the maximum
continuous power that the system will handle and often appears very conservative. In reality, as music
program is far from continuous in nature, the peak power of the system is much higher – up to ten times the
continuous figure. Any limiter, which is to protect the driver from damage, must be able to fulfil the following
tasks:
- Have an attack time which is calculated to allow transients through but keep the RMS level below the
speaker manufacturers specification;
- Have a release time which is sufficiently long to avoid the limiter itself modulating the program;
- Be intelligent enough to adjust the envelope of the limiter according to the frequency content of the
program material.
The RMS limiters are capable of performing all these tasks. The only parameter that the user must set
manually is the threshold, and it is crucial that this is done correctly.
The peak limiter follows the RMS limiter, has only two parameters to adjust – the release time and the
threshold. Note that the threshold is set to be a minimum of 2dB above the threshold of the program limiter –
setting the threshold to “10dB above” means that no more than 10dB of overshoot above the threshold of
the program limiter will ever be allowed.
The release time can also be automatically set if the RMS limiter has automatic time constants enabled
and so are set by the high pass filter frequency for that channel.
