Crossover
Purpose
Crossovers divide the frequency spectrum into two or more bands that can be processed independently and sent to separate power amplifiers. Crossovers are constructed of Low Pass and High Pass Filters, and their controls relate to the corresponding controls of their component filter sections. Crossover devices have been constructed with 2, 3 and 4 bands and maximum slopes of 24, 36 and 48dB/octave. Crossovers consume DSP resources proportional to the number of bands and their maximum filter slope. Select the smallest Crossover which fulfills the requirements for your application. Once compiled, filter slopes may be adjusted downward with the Slope Controls but no DSP resources will be recovered by doing this.
Controls (Standard and Deluxe)
Indicates an overload condition in the crossover filter section. Such an overload condition can be rectified by reducing either the Input_Level or the Output_Level.
Allows inversion of the polarity of the signal at the output of each crossover frequency band. The crossover filters generate phase shifts dependent on Filter Type and Slope. For correct combination of frequency components the Output Invert controls of each band should be set as described in Crossover Output Invert Recommendations
Allows muting the output of each crossover frequency band.
Allows adjustments of the crossover points. The first control sets the frequency at which the lower frequency band begins to cut out. The second control sets the frequency at which the higher frequency band begins to cut in. For optimally smooth combination of frequency components, the two Crossover Frequency controls associated with a crossover point should be set to the same frequency.
Allows adjustment of the output level of each crossover frequency band.
Additional Controls in Deluxe Crossover
Inverts the polarity of the signal entering the crossover filter sections.
Mutes the signal entering the crossover filter sections.
Adjusts the level into the crossover. Adjustments made to this control are reflected in the input meter.
It is possible to create an overload condition within the crossover device if this control is set above +0dB. Such an overload may be shown on the input meter.
Shows the RMS signal level entering the crossover filter sections.
Setup... Block
Different digital filtering techniques produce different Response Characteristics allowing the crossover to be tuned to specific applications. Choices are Bessel, Butterworth or Linkwitz-Riley.
Note: The Filter Type selection affects all bands of the crossover.
Another Note: When the Linkwitz-Riley filter type is selected, Filter Slopes are only available in even multiples of 12dB/octave. Slope control settings may be changed when the filter type is switched to Linkwitz-Riley to enforce this constraint. Slope settings will not be restored when switching back to Butterworth or Bessel filter types.
The slope indicates the selectivity of the crossover between frequency bands. The first control sets the slope at which the lower frequency band cuts out. The second control sets the slope at which the higher frequency band cuts in. For Butterworth or Bessel filter types, 6dB/octave to maximum slope for the device selected (absolute maximum of 60dB/octave) in 6dB/octave increments. For Linkwitz-Riley filter type, 12dB/octave to maximum slope for the device selected (absolute maximum of 60dB/octave) in 12dB/octave increments.
For an optimally smooth combination of frequency components, the two Slope controls on adjacent bands corresponding to crossover point should be set to the same slope. Different slopes can be specified at different crossover points without adversely affecting signal combination.
Schematic
2 Output Crossover
3 Output Crossover
4 Output Crossover
Advanced Topic
The Crossover Devices are constructed of a Meter, a Level, High Pass Filters and Low Pass Filters. In situations where the metering and/or input level control is not required, they may be removed by editing the device resulting in some savings of processing power.