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Xmax Excursion Limiter
The Excursion Limiter protects the driver against excessive linear movement of the cone and voice-
coil which could otherwise cause mechanical damage. Since this movement (excursion) is largely
related to the inverse of the signal frequency, drivers are prone to being damaged by very low
frequencies. This limiter is progressively more sensitive at lower frequencies and, rather than varying
the gain to provide the limiting action, it uses a sliding high-pass filter to progressively curtail the
low-frequency response, effectively limiting the linear excursion to below the X-max specification of
the driver.
To set the limiter up, it is necessary to know the shape of the family of Excursion vs. Frequency
curves of the driver for various drive voltage levels. A curve should then be chosen where the slope is
high where it passes though the specified X-Max value for the driver. The peak voltage and frequency
of this point should then be noted.
The Xmax limiter is usually then set up using just two parameters:
Threshold
– the peak voltage of the point arrived at above. This is calibrated at the output of the
amplifier. The Excursion Limiter can be defeated by setting Threshold to the maximum "Off" value.
Frequency
– The frequency at which the above threshold voltage is appropriate.
Min
A further parameter "
" may also be available for more advanced applications. This allows the
increasing limiting action at lower frequencies to level-off below a certain frequency. In most
application, this would be left set to its default value of 5Hz.
Setting
Note: For further information on setting up limiters, please see the Application Note DE3457
Up Limiters
.
Bridge
When an amplifier pair is set to Bridge Mode, it uses two amplifier channels to drive one loudspeaker
with greater power. In this mode, only one set of Output controls is active per pair of amplifier
channels since both of the amplifiers in the pair are driven with the same signals, as determined by
before
the left-hand (lower numbered) channel of the pair controls. Bridge settings should be set up
recalling
Drive Module
Presets. Module Preset Recall will see a bridged pair of outputs as a single
channel.
Bridge Mode is enabled or disabled in the setup page of the System Engineer panel. When enabled,
the Bridge indicator on the device will be illuminated between the bridged channels.
When Bridged, the partner (even numbered) channel will not show any signal on the limiter meter,
neither will you be able access any of its parameters for adjustment. The Amplifier protection
indicator however will still operate.
Routing
source
The setup button in the System Engineer panel allows you to change the
from which each
output derives its drive signal. An output can be driven from any DSP input. This routing is the
fundamental means by which Drive Modules are created. Routing should always consume outputs
consecutively alphabetically and numerically. However, non-consecutive Drive Modules may be
Recalling Components
drive module
created using manual routing and
. See the
section of this user
manual for more information.
Driver
load
The optimal drive level may be adjusted for a given driver impedance using the
parameter by
clicking the gearwheel and selecting the appropriate output. See
Load
Matching.
The live measured impedance value is also shown in this view page. Since the device can only
measure this when there is a signal, the impedance is indicated as "?" when there is insufficient signal
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