An active crossover gets its input from the  pre-amp and sends the signal to multiple outputs, each connected to a power amp.
Each power amp drives only one driver.
    As the passive crossover is removed out of  the power circuit, the amp has now full control over the driver (damping).
The crossover is working on line level. This  allows the use of active components (opamps).
    This allows for more functionality than  possible with passive components.
Crossovers are covered in more detail here.
Active crossovers can be implemented using an analog circuit or using DSP.

The Model 10B features independently selectable crossover points for high-pass and low-pass, in case the speaker installation requires slightly overlapped, (or slightly staggered), response curves for the drivers. You can also independently select crossover slope, from 6, 12, or 18dB/Oct., where one driver requires faster cutoff than another in the same system. A fixed frequency plug in Linkwitz-Riley alignment with steep rolloff curves of 24 dB/Oct. is also available.

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DSP is using a processor to implement the crossover.
Instead of analog components, why not use a processor.
Playing  Redbook audio (CD) is 44.100 sample a second.
    Obvious the  processor has 1/44100= 0.000023 of a second to do the processing.
    In case of 192 kHz this is 0.000005 s.
    Obvious a DSP chip must be fast.
    The word length is also important to avoid audible artifacts due to  quantization errors.



The HDP must be placed between the pre- and the power amp.
The signal from the pre-amp is converted to digital.
The DSP is applied and the result is converted by the DACs.

DCN28 is a digital crossover, pre-amplifier and room correction in one unit.
DCN28 is supplied with the XOverWizard II advanced software which is a graphical tool to manipulate with inputs, outputs, gain, crossover frequencies, crossover slopes, equalization and delay. The software features measurement engine, post processing tools, optimizer engine with target option, output listing and direct transfer to the crossover setup environment.

A true digital amplifier, accepting PCM input and using PWM (Pulse Width
      Modulation) to amplify.
      The M/S-2150 XDM crossover package is designed to support front panel crossover
      design, thus totally eliminating the need for computer interface. All crossover
      filter design algorithms are implemented in the M/S-2150 XDM internal processing
      unit. Crossover filters are designed and loaded in a split of a second for
      immediate listening and evaluation. 
      Supported crossover filters are  Butterworth and    Butterworth squared 
      
      All filter cutoff frequencies can be set anywhere between 10 and 24 KHz with
      a resolution of 1 Hz and with  filter slopes from 6 to 72 dB/octave. 
As it is a 2 channel amp you can only use this with 2 way speakers.
You need 2 amps to drive a 2 channel 2 way speaker setup.
Amps can be synchronised.

• multi-point measurements of all loudspeakers
      • time-frequency analysis: the loudspeaker and the room are   separately equalized
      • automatic optimization of amplitude and phase response   according to target curves
      • intelligent active crossovers: automatic alignment of delays and gains for every   driver 

      Audio Performance
      Freq Response: +/- 0.1dB (20 to 30kHz)
      Dynamic Range: 115 dB typ (unweighted)
      CMMR: >100dB (50 to 10kHz)
      Crosstalk: < -100dB
      Distortion: 0.002% (1kHz @ +4dBu)
      
        Digital Audio Performance
      Processor (DSP): 40-Bit Floating Point
      Sampling Rate: 96kHz
      Analog Converters: Super Performance 24-bit
      Propogation Delay: 1.5ms
      1.75 – 7.75ms with FIR
      
        Audio Control Parameters
      Gain: -40 to +15dB in 0.25 dB steps
      Polarity: +/-
      Delay: Up to 650 ms per I/O
      
        Equalisation
      Variable Equalizers: 8 per I/O
      Type: Parametric, Hi-shelf, Lo-self,
                Phase (1st and 2nd order)
      Gain: -30 to +15dB in 0.25dB steps
      Bandwith: 0.02 to 2.50 Oct (Q=0.5 to 72)
      Graphic EQ: 1 per Input, 31 Band 1/3 Oct steps
      
        Crossover
      IIR Filter Type:
      2 Individual filters per input & output.
      Type - Butterworth, Linkwitz-Riley & Bessel.
      
      FIR Filter Type:
      2 Individual filters per Output.
      Type - Multi-Tap.
      Slopes: 6 to 48dB per Oct for IIR
      50 to1200 Taps for FIR
You can use software on a PC to implement an active crossover.

The DCN23 Kit is a stereo/dual mono 3-way stand alone digital crossover.
• High performance Burr-Brown converters
  • 24bit resolution
  • 96kHz sampling frequency
  • XOverWizard software
  • Optical isolated USB interface
  • 48 biquads total processing filters
  • 76bit processor precision
  • 21mS total delay option
  • Latency 1ms
  • 4 layer high performance PCB
  • Decoupling at all active components

The module has two 400Watt UcD modules implemented and is also available with a digital audio input AES/EBU, called the PSC2.400d version. The supply voltage is provided by a Switched Mode Power Supply (SMPS400) module, also a module from Hypex Electronics.
A PC controls the PSC2 through the USB port. This connection is used to upload the configuration and filter settings. It will also be possible to update the firmware through USB.


The “DLCP” is a complete hardware/firmware platform for digitally filtered (6 channels) and corrected active multiway loudspeakers. Digital response correction allows significant extra degrees of freedom in the acoustic design of a loudspeaker. Driver parameters can be selected for best efficiency and distortion instead of electrical damping, and the cabinet can now be fully optimized for radiation pattern.