Output Eq; Limiters; Rms Limiter; Peak Limiter - powersoft M30D HDSP+ETH User Manual

FIGURE 30: The input eq layer.

10.8.3 Output eq

This page's general appearance is similar to that of the Input
Equalizer page, but presents several important differences.
The Output Eq. curve the amplifier employs is meant to be
created from the speaker manufacturer's data for the particular
loudspeaker cabinets or arrays the amplifier will be driving. It
provides a range biquad filter that can act as crossover or generic
IIR filter. From this page, the frequency response of each channel
can be adjusted in several ways. Discrete time delays can also be
inserted. The presence of every output eq. present in the device
layout is reported on the tabbed channel on the bottom left
hand side of the screen. The frequency response curves, together
with other View items, are color coded: blue for channel 1, red
for channel 2, green for channel 3, orange for channel 4. Every
channel allows regulation of filters, mute, gain, delay and polarity.
The displayed frequency response (and/or phase response) curve
is always obtained as the combined response of all currently active
filters.
FIGURE 31: The output eq layer.

10.8.4 Limiters

The function of the limiters is to protect voice coils from
burning out due to excess power being delivered over an extended
period of time or from excessively large signal peaks by limiting the
maximum output voltage of the amplifier. The limiter window is
accessible by clicking on the limiter block in the device layout view.
Every channel limiter is color coded: blue for channel 1, red for
channel 2, green for channel 3, orange for channel 4.

10.8.5 RMS limiter

Electromechanical transducers are highly inefficient; as such
they transform a significant amount of input power into heat. The
function of the RMS limiter is to protect the voice coils of speaker
FIGURE 32: The limiters dialog window.
drivers from burning out due to excess power being delivered over
an extended period of time. The RMS limiter is set by selecting a
desired maximum power value but acts by limiting output voltage;
by applying Ohm's law with a fixed reference 8 � load, the output
voltage level corresponding to the desired maximum output
power value is calculated as the square root of power times the
load resistance (8 �). It is possible to set the values of:
f Threshold in watts, with respect to an 8 � load.
f Attack time is the time between the moment the output
voltage exceeds the threshold and the moment of the onset
of the limiting action.
f Hold time is the length of time during which the limiting action
is maintained before the gain returns to normal levels because
the output voltage drops below the threshold level.
f Release time is the length of time over which the limiting
action is reduced and the gain is returned to normal following
the drop of the output voltage below the threshold level.

10.8.6 Peak limiter

The function of the peak limiter is to protect voice coils from
excessively large signal peaks by limiting the maximum output
voltage of the amplifier. It's possible set the values of:
f Threshold in volts, is the amplifier max output voltage level
corresponding to the maximum displacement of the speaker
diaphragm.
f Hold time is the time over which the limiting action is
maintained before the gain level is returned to normal after
the output voltage drops below the threshold.
f Release time is the length of time over which the limiting
action is reduced and the gain is returned to normal following
the drop of the output voltage below the threshold level.

10.8.7 Damping factor correction

The effect of cable resistance on a high power amplifier
performance becomes significant at low frequencies, as the cable
resistance can affect the output stage damping factor. Powersoft
Damping Control is a proprietary algorithm which compensates
for cable resistance. The user can enter cable parameters and the
algorithm calculates and applies the appropriate correction. A tool
to calculate the cable resistance is provided.
Damping factor correction can also be used to fine tune low
end nuances: a negative resistance leads to a punched bass while a
positive resistance leads to a tailed bass.
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