26 | M-Drive | User guide
16 : 5.6.1. Disable External Knob
By clicking on this box is possible disabling the external attenuation knob, this must be
done in case of external processor like DSP-4 connected to M-Drive.
16 : 5.6.2. Current Limiter
Set a threshold limit and the attack/release time for the average (rms) output current.
16 : 5.6.3. Power Limiter
Ensures that the real part of the average output power does not exceeds the limits set
by the user.
16 : 5.6.4. Current Clamp
The Current Clamp is a faster acting current limiter. Current Clamp is meant to limit
spikes of current, effectively protecting the output stage and the connected loudspeaker
from dangerous high peak current: this is different respect the short circuit protection that
works by sensing decreasing rails values. The current threshold value does not indicate the
maximum output current, but the current level at which the limiter will start sensing spikes
of current. Output current level can exceed the clamp threshold considerably due to the
internal limiter design.
16 : 5.6.5. Efficiency Protection
Set the minimum threshold limit of the measured efficiency that triggers the protections
on the amp module. The pressure sensor continuously measures the acoustical output
power developed by the diaphragm: when the acoustical output power falls under
the expected output power, the efficiency of the system lower accordingly. This can
be occasionally caused by a fault either in the amp module or in the transducer motor.
Powersoft recommends to set the efficiency protection at least to 1/3 of the value of the
reference loudspeaker efficiency (Ref eff. no%, see below). The value 0 (zero) switches off
the efficiency protection. If the pressure sensor is not used, set the efficiency protection to
0 (zero).
16 : 5.6.6. Excursion Limiter
The excursion limiter keeps the loudspeaker cone displacement within a user defined
range. The threshold cone excursion is set in mm. The excursion limiter works through
a current loop, dynamically changing the value of a resistance proportionally to the
displacement of the cone with respect to its resting position. It is important to note that
this position is estimated; its accuracy depends on the precision of the connected speaker
physical parameters entered in the Physical Speaker Parameters section in the advanced
parameters window (see below). The Gain (ohm/cm) parameter sets the displacement/
resistance conversion factor, so as to regulate the intensity of the limiting effect. For a given
cone displacement, a higher gain value yields a more severe limiting action. The release
time determines the time needed for the limiter to release the cone. Please note that the
maximum cone excursion set in this window only determines the cone displacement value
that activates the effect of the limiter; it does not represent the maximum excursion the
cone will display. The limiter’s internal design allows for a certain margin between maximum
displacement threshold value and effective cone displacement, the latter being potentially
higher.
