• One operates on the whole frequency range (wide band VCA).
• The other element works selectively as a dynamic equalizer (LF-VCEQ).
Depending on the nature and origin of the servo signals, either one or the 2 combined elements is used to
process the Audio signal. This feature allows more efficient processing while reducing audible effects.
Displacement control
The signal from the sense input is fed through a shaping filter producing a signal proportional to the voice
coil displacement. This control signal is compared to a fixed value and if exceeded, the LF-VCEQ is
activated with very short attack time to reduce speaker excursion.
Temperature control
Sense input is fed to a shaping filter to create a voltage proportional to the instantaneous voice-coil
current. The signal is integrated over time to simulate heat buildup in the specific driver. When the
resulting voltage exceeds a preset threshold, the VCA is activated to limit the voice coil temperature within
its safety range. On PS15TD and on PS10TD (serial number above 868), power compression is also
simulated by lowering the high frequencies when temperature protection is acting on the bass
loudspeaker.
Dynamic control
To reduce audible « pumping » effects due to very long time constants of temperature detection signals,
an alternate integration is also processed with a shorter time constant. Whilst anticipating the temperature
protection and reducing its unwanted effects, action of this signal also improves dynamics control.
Peak Limiter
The above mentioned devices provide reliable protection against potential speaker over-heating and over-
excursion. Nevertheless driving the cabinets at very high peak voltages (with oversized amplifiers) as well
as delivering distorted signals might be dangerous for the speakers. The Peak limiter is both useful for :
• Maintaining good sound quality at high levels (it will reduce amplifier distortion).
• Increasing protection reliability (limiting peak voltages to levels that speakers can permanently withstand,
and reducing the occurrence of subsonic signals delivered by overloaded amps)
.
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