T-44/48 Series Operation Manual
31
T-44/48 Series | rev.
firm. 1.258 and above
4.3.7 Limiters
The T-44/48 Series includes three limiters in the output signal path.
Please note that
whilst the Limiters in this product offer some degree of protection for amplifiers and drivers, Exel
Acoustics and its Tecnare brand cannot be held responsible for any damage which might occur
in these components.
4.3.7.1
VX Limiter
This is a peak-detecting signal limiter. The VX Mode parameter determines the style of
limiter. When Virtual Crossover (VX) mode is off, the limiter is controlled in a conventional
manner; the only controls being Threshold and Overshoot.
The Overshoot limiter prevents the signal from exceeding threshold during the attack
phase of the main limiter by more than a predetermined amount. The optimal Overshoot setting
is usually about 8dB. Lower Overshoot settings will sound progressively ‘harder’.
When VX mode is engaged, the user can choose the crossover point of a ‘virtual
crossover’, which gives two limiters per output so the user can individually limit the drivers in a
passive 2-way enclosure using individual thresholds, and optimised attack and release
characteristics for each. The Threshold of the second ‘Hi’ limiter is set relative to the threshold
of the first ‘Lo’ limiter.
The effect of the VX threshold and split frequency on the Limiter curve can be seen in
System Engineer.
This Limiter introduces some delay. In non-VX mode, this delay will depend on the
lowest high-pass frequency used in the crossover filters in a given Drive Module. In VX mode,
the delay is related to the Split frequency. This delay will be applied to all of the outputs in a
given Drive Module to keep them in phase.
Also see Latency Delays on page 33.
4.3.7.2
Tmax Thermal Limiter
The Thermal Limiter is intended to protect the driver against damage due to over-
heating. It models the temperature of the driver, and constrains the output signal level in order
to keep the average output power below a predetermined limit, applying attack and release
characteristics to go some way towards modelling the complex thermal circuit of a driver’s voice
coil and magnet assembly.
Three parameters are available for adjustment:
Threshold
– the continuous RMS voltage which the driver should be able to withstand. This is
calibrated at the output of the amplifier. The Thermal Limiter can be defeated by setting the
Threshold to the maximum “Off” value.
Attack
– The time-constant of the speed at which the driver heats up (in seconds).
Release
– The time-constant of the speed at which the driver cools down (expressed as a
multiple of the Attack time).
1
LIM
Thresh
Over
VxMode
Out_nam
20.0dB
2.0dB
Off
