Page 54/82
NEXO
A
NALOGUE
PSTD
C
ONTROLLERS
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. 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 amS12)
