Active crossover calibration (Altitude only)

Summary:

• What is an active crossover?
• Trinnov-specific capabilities
• Prerequisites before starting the calibration
• Filters available in Expert mode
  • Filter types
  • Filter slopes
• Step 1: set the crossover filters 
  • Basic mode
  • Expert mode
• Step 2: calibrate each speaker individually
  • Basic mode
  • Expert mode
  • Impulse response alignment
  • Power and direct response

• Next step in the calibration workflow
  
  

 

What is an active crossover?

An active crossover replaces the passive crossover network inside a multi-way loudspeaker.

Instead of driving the speaker with a single amplifier channel, the incoming signal is split into multiple frequency bands, each feeding a dedicated driver (woofer, midrange, tweeter, etc.) through its own amplifier channel.

This approach provides significantly greater control over:

• Crossover frequencies and slopes
• Time alignment between drivers
• Gain and polarity per driver
• Overall acoustic integration of the loudspeaker

 

 

Trinnov-specific capabilities

Trinnov's semi automatic active crossover calibration system is unique and supports:

• Up to 4-way active speakers
• Semi-automatic calibration driven by real acoustic measurements
• Both Basic and Expert modes
• Time-domain and frequency-domain analysis tools
  
  

 

Prerequisites before starting the calibration

Before starting the active crossover calibration, the following conditions must be met:

• Speakers declared as multi-way in the Routing page
  (see the dedicated Routing Configuration article)
• Each speaker way:
  • Properly connected to the correct amplifier channel or driver
  • Verified individually using pink noise
• Manufacturer specifications available, including:
  • Recommended crossover frequencies
  • Filter types and slopes

 

Filters available in Expert mode

In Expert mode, the Altitude allows full control over crossover filter types and slopes.

Filter types

Linkwitz-Riley (LR)

The default Trinnov crossover type.

• Flat summed response at the crossover point
• In-phase summation between adjacent ways
• Smooth transition between drivers

The most commonly used configuration is LR4 (4th order, 24 dB/oct), which offers an excellent balance between acoustic separation and summation accuracy.

Bessel

Optimized for time-domain behavior.

• Maximally flat phase response
• Best transient preservation
• Gentler roll-off than other filter types

Because of the gradual transition, the summed amplitude response may not be perfectly flat. Bessel filters are typically chosen when transient accuracy is prioritized over strict frequency-domain summation.

Butterworth

Optimized for magnitude response.

• Maximally flat magnitude per section
• Each section is –3 dB at cutoff

When summed, Butterworth filters can produce a +3 dB peak at the crossover frequency unless compensated. They provide a steeper roll-off than Bessel filters, but less ideal summation than Linkwitz-Riley.

 

Filter slopes 

The filter order determines the attenuation per octave. Higher orders provide steeper separation between drivers but increase sensitivity to alignment errors.

Linkwitz-Riley		Bessel		Butterworth
Order	Slope	Order	Slope	Order	Slope
L-R 2	12dB/Oct	Bsl 2	12dB/Oct	Bwth 1	6dB/Oct
L-R 4*	24dB/Oct	Bsl 3	18dB/Oct	Bwth 2	12dB/Oct
L-R 6	36dB/Oct	Bsl 4	24dB/Oct	Bwth 3	18dB/Oct
L-R 8	48dB/Oct			Bwth 4	24dB/Oct
				Bwth 6	36dB/Oct
				Bwth 8	48dB/Oct

 

Step 1 - Set the crossover filters

Basic mode

You only need to define the crossover frequency for each speaker.

All other parameters are handled automatically using Trinnov’s default filter model.

 

Expert mode

Each speaker way is configured independently:

• High-pass and low-pass filters
• Crossover frequency
• Filter type
• Filter slope
  
  

The filter graphs display:

• The theoretical response of each filter
• The reconstructed response, showing how adjacent ways combine in both frequency and phase

These visualizations are essential to understand the real impact of filter choices before measuring the speaker.

Horn EQ options

Two optional compensations are available:

• Constant-directivity horn EQ: +6 dB/oct from 3 kHz
• Half constant-directivity horn EQ: +3 dB/oct from 3 kHz

These are designed to compensate for the natural high-frequency roll-off of horn-loaded speakers, commonly used in commercial cinema environments.

 

 

Step 2 – Calibrate each speaker individually

Unlike a full system calibration, active crossover calibration is performed speaker by speaker, and not globally.

Each speaker is measured one way at a time, using a test signal that is already filtered according to the crossover settings defined in the previous step.

• A filtered test signal is sent to each speaker way in sequence
• Measurements are performed independently for each driver
• The goal is to acoustically align all ways so they behave as a single coherent loudspeaker

 

Basic mode

In Basic mode, the process is fully automatic.

Once the measurement is complete, you can proceed to the next step unless an error message is reported.

No manual adjustment is required at this stage.

 

Expert mode

In Expert mode, the Optimizer computes and exposes the parameters required for precise driver alignment:

• Delay
• Gain
• Polarity

These values are calculated automatically but remain editable, allowing expert users to refine the alignment when needed.

In addition to the crossover filter graphs, three diagnostic representations are available to validate and fine-tune the result.

Impulse response alignment

The Impulse Response graph displays the measured impulse of each individual driver after the calculated delay, gain, and polarity have been applied.

This graph allows you to:

• Verify that all speaker ways are time-aligned at the listening position
• Confirm correct polarity between adjacent drivers
• Identify misalignment between acoustic centers of the drivers

Correct impulse alignment is a prerequisite for meaningful crossover integration.

Power and direct response representation

This representation illustrates one of Trinnov’s most distinctive calibration principles: combining time-domain and frequency-domain analysis to achieve faster and more reliable results.

The graph overlays two traces:

• Power response
  The reconstructed response of the full loudspeaker, combining all ways as measured with the calculated delay, gain, and polarity. This representation includes room interaction and off-axis energy.
• Direct response
  The impulse response filtered in the time domain to exclude late reflections, isolating the direct sound arriving at the measurement position.

At the crossover region, both responses should be as close as possible.

A close match indicates that acoustic energy is correctly radiated toward the listening position, while a gap between the two typically reveals driver misalignment, causing energy to be radiated in unintended directions.

Both representations must be interpreted together to achieve optimal crossover integration.

Next step in the calibration workflow

Once the active crossover calibration is complete, you can proceed to the final decision in the calibration workflow: perform a single-point or multi-point full system measurement for the Optimizer

Refer to the Single or Multiple Measurements article to choose the approach best suited to your room and listening area.