Active crossover

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 analogue circuit or using DSP.

Analogue

Bryston 10B $3050

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.

Marchand XM44 3 way $1200

• Available 1-way, 2-way, 3-way or 4-way.
• Steep 24 dB/octave 4-th order slope (Linkwitz-Riley) standard. Up to 48 dB/octave optional.
• Any slope available (6,12,18,24,30,36,42 or 48 dB/oct)
• Asymmetric or symmetric slopes (different slopes can be mixed)
• Crossover frequency 20Hz - 20 KHz.
• Subwoofer summing switch.
• Standard 12 position attenuators, 1 dB/step, for level control on all outputs; 24 position attenuators optional.
• Options: Balanced outputs/inputs, baffle step compensation, notch/boost filters, delay sections and bass boost filter (Linkwitz transform).
  

Rane AC 22S Active Crossover $ 449

• Stereo 2-Way, or Mono 3-Way
• Linkwitz-Riley Alignment with 24 dB per Octave Slopes
• Adjustable Driver Alignment Delays
• Infrasonic, Ultrasonic and RFI Filters
• Low Output Muting (2-Way)
• Mono Sub Output Option
• Constant-Directivity Horn EQ Option
• Input & Output Level Controls
• Fully Active Balanced XLR Inputs & Outputs
• Internal Universal Power Supply (100-240 VAC)

DSP

DSP is using a processor to implement the crossover.

Instead of analog components, why not using 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.

Behringer DCX2496 $ 439.99

• 3 analog inputs (one suitable as digital stereo AES/EBU input) and 6 analog outputs for maximum flexibility
• High-end AKM® 24-bit/96 kHz A/D and D/A converters for ultimate signal integrity and wide dynamic range (113 dB)
• Integrated sample rate converter for easy connection of external digital signals with sampling rates from 32 to 96 kHz
• Precise dynamic EQs for level-dependent equalization and extremely musical parametric EQs, selectable for all inputs and outputs/
• Several types of EQs (LP/BP/HP) for each input and output/
• "Zero"-attack limiters on all output channels for optimal speaker protection/
• Four different mono and stereo output operating modes
• Individual crossover filter types (Butterworth, Bessel and Linkwitz-Riley) with selectable roll-off characteristics from 6 to 48 dB/octave
• Adjustable delays for all inputs and outputs-allow manual or automatic correction for room temperature, phase and arrival time differences
• Additional sum signal derived from the A/B/C inputs offers a fourth internal input signal
• Future-proof ULTRADRIVE PRO software enables single or multi remote control via PC through RS-232 and RS-485 interfaces
• Link option via RS-485 network interface enables cascading of several ULTRADRIVE PROs
• 60 user-defined internal presets storable via PC software or on PCMCIA card
• Open architecture assures easy software updates
• Servo-balanced, gold-plated XLR connectors for all inputs and outputs
• High-quality components and exceptionally rugged construction for long life and durability
• Internal switch-mode power supply for maximum flexibility (100 - 240 V~), noise-free audio, superior transient response plus lowest possible power consumption

DEQX HDP-3 Preamp proccesor AUD 6575

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.

• Provides DEQX Calibrated™ speaker correction for passive speakers
• Provides DEQX-HD™ speaker correction for up to 3-way active speakers
• DEQX-HD™ active crossovers; 48dB/octave to 300dB/octave linear-phase
• Traditional active 3-way crossovers from 6dB/octave to 48dB/octave
• Frequency-response of speakers typically corrected from 6dB range to 1dB
• Automatically corrects phase and group- delay over typically 3ms window
• 32-bit, floating-point, 240-MFLOPS processing with dual SHARC DSPs
• Audiophile 24-bit 96kHz ADC-DSP-DAC processing and conversion
• Provides anechoic measurement and detailed display for speaker correction
• Provides room-measurement/display (non-anechoic) for room correction
• Calibration Kit provides DEQX-calibrated measurement microphone
• Two analog inputs: Unbalanced (2 x RCA) and Balanced (2 x XLR)
• Two stereo digital inputs: S/PDIF (1 x RCA) and AES/EBU (1 x XLR)
• Six analog outputs: unbalanced (6 x RCA)

Ground Sound DCN28 € 4.217,00

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.

• 4 Digital Inputs (AES3-Coaxial-Optical)
• 2 Balanced Stereo Analogue Input
• 1 USB Audio Soundcard Input (galvanic isolated)
• Digital controlled analogue attenuation on all outputs
• 4-way stereo true balanced outputs
• Digital PCM signal 32kHz-192kHz
• Included XOverWizard II advanced software
• Included Philips SRU6006 Remote
• Optinal application code for Philips Pronto remote
• Optinal code for Logitech Harmony Remote
• Big Dimmerble Dot Matrix display
• All in one Encoder Button controlling menu and values
• 4 Power Amplifier remote trig outputs for 12V relays
• Converter Resolution 24bit
• Sample rate 96kHz
• Total processing power: 180 biquads IIR
• Frequency response: 5-48kHz (-3dB)
• Latency input-output about 1ms
• Low Standby Power
• Dimensions: 430mm x 290mm x 100mm

HOLM Acoustics DSPre 1

Most active crossovers expect a analogue input.
If the crossover is done using DSP inevitably the analogue input has to be converted to digital (AD) first. Then the DSP is applied. The resulting signals are send to the DAC’s and converted to analogue again.

If your audio is digital you can save two DA – AD conversions if the active crossover uses DSP and accepts digital inputs. Holm is one of the very few I know applying the DSP straight on the digital input.
However it also accepts analogue inputs. They have to be AD'ed first of course.

• DSPre design:
  The DSPre unit is designed with the objective to have the least clutter in terms of controls.All other control of the quite advanced DSPre is done from the PC software DSPreLab.
• DSPre software DSPreLab:
  DSPreLab is the full featured PC application that transforms DSPre to a comprehensive speaker measurement tool and hold the power to transform these measurements into state of the art digital filters to run real-time on the DSPre. No PC needs to be connected during normal playback. The filter-type run on DSPre is FIR "Finite Impulse Filter" hence the name DSPreLab.
  
• Room adaption
• Individual filtering and correction of every driver
• Perfect summing of driver outputs
  
• Calibrated measurement microphone
  
• Jitter removal from any digital source - "Clock Flawless" system
  
• USB audio playback and recording of any input (adaptive 16 bit/48 kHz)
  
• Digital inputs TOSLINK, SPDIF, AES/EBU:
  Sample-rates from 11,025kHz up to 196kHz and are sample-rate converted to the internal 44,100 kHz processing rate.
  
• Analog to Digital inputs natively, no extra cost for A/D modules:
  DSPre do all the calculation digital domain and therefore analog input have to be converted into digital signals. Our preamplifier has two stereo Analog to Digital Converters for analog line signal. The ADC sensitivity can be adjusted to match the signal level of your analog source. ADC's convert to 24bit at 88,200 kHz Sample-rate.
  
• 6 analog outputs for stereo bass, mid and tweeter:
  The output digital to analog converters are module based in a manner to comfort your system. For conventionally filtered speakers only one stereo DAC is used. For 2-way and 3-way systems a second and third DAC is mounted, one DAC output for every speaker unit. The DACs are 24bit and are up-sampled to 352,800 kHz and anti-aliasing filtering is made outside the frequency band of the human ear, deemphasizing analog component performance. Volume control is achieved by lowering the DAC reference current for damping in the region 0 to -32dB, from -32dB and down the volume is adjusted inside the DACs 24bit multiplier. This way a analog attenuator is omitted in the signal-path, and there is only a minor bit-resolution-penalty at very low listening-levels.
• A model with digital out only is also available. This allows you to use the DACs of your choice.
  
• Band-less equalizer to tune to your preference:
  The DSPreLab software includes a band-less equalizer who have more than 16000 individual frequency-discretions for setting up to 100 EQ points.

Tact M/S 2150 XDM USD 4800.00

• 5 digital inputs and mic input
• Level balancing and time alignment
• Computerless digital crossover package
• Full blown 12 band parametric EQ
• 2-channel digital amplification width full spectrum Dynamic Room Correction

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.

Trinnov ST2 € 5890

• 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

PC

A multi-channel soundcard and the appropriate software allows you to do the DSP on a PC.

The Building of a Pure Digital System by Arthur Cheng gives a detailed description how to do it.

Thuneau - The Frequency Allocator

$149.00

DIY

Ground Sound DCN23 € 693,00

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

Hypex PSC2.400 € 347,00 excl. VAT

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.

Hypex DLCP € 550,00 excl. VAT

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.

MiniDSP $99