Danley DNA SC48, Руководство пользователя

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When VX mode is engaged, the user can
choose the crossover point of a ‘virtual crossover’, which
incorporates 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
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).
Also see Amplifier Gain
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.