Convolution is the process of multiplying the frequency spectra of our two audio sources: the input signal and the impulse response. By doing this, frequencies that are shared between the two sources will be accentuated, while frequencies that are not shared will be attenuated.

This phenomenon occurs when the input signal adopts the sonic characteristics of the impulse response, resulting in enhanced frequencies that are commonly present in both the impulse response and the input signal.

Steps to configure MIMO Convolver

1. Navigate to the IVP RTA tab and select Advanced from the ribbon bar. This opens the RTA Settings dialogue box.
2. On the RTA Settings dialogue box, select the Plugins tab.
3. Click on the folder icon to browse the xAF library path.
4. Set the port number under the Port box.
5. Enable the Bypass option (optional), if you prefer the input to be passed directly to the next plugin or output without undergoing any processing.
6. Click on Apply. The number of inputs, number of outputs, and plugin type will be automatically updated based on the provided signal flow.
7. Switch to the MIMO Convolver tab.
8. Set the number of Inputs, Outputs, and Filter Taps.
   

You can configure coefficients in 2 ways.

• Configure coefficients in Panel
• Configure coefficients through virtual prediction

Configure coefficients in the Panel

1. On the MIMO Convolver tab, click on Configure Coefficients. The Configure Coefficients panel launches with 2×2 filters.
   
2. Adjust the coefficients by either setting them to a flat value or importing them using CSV/XML files.
3. Click on Tune, after assigning coefficients.

A toast message “Tuning applied” appears.

Amplitude/Phase: When the coefficients are given and the “Amplitude/Phase” option is selected, the graph displays the value.

Coefficients:  When the coefficients are given and the “Coefficients” option is selected, the graph displays the values as per the below figure. You can change the graph style using the “Chart Style” option.

Line chart style: when “Chart Style” is selected as Line, the Coefficients graph.
Dot chart style: when “Chart Style” is selected as Dot, the Coefficients graph.

Group Delay: When the coefficients are given and the “Group Delay” option is selected, the graph displays the values.

Curves Legend: This option allows you to show the details of which graph tab (Amplitude/Phase, Coefficients, Group Delay) is selected.

On the selection of the Amplitude/Phase graph tab Curves Legend will show the below information.
On the selection of the Coefficients graph tab and Chart Styles ‘Dots’, Curves Legend will show the below information.
On the selection of the Coefficients graph tab and Chart Styles ‘Line’, Curves Legend will show information.
On the selection of the Group Delay graph tab, Curves Legend will show information.

Additional Functionalities

• Flat: This is used to make the graph flat by making coefficients to 0.
• Import: This function is used to import the coefficients for a single active filter. Click on the “Import” button, then enter the file path and click Ok.
  All coefficients for the selected filter will be imported, as shown in the graph. If the number of coefficients does not match the number of taps, a warning pop-up will appear. Click ‘Yes’ to import available coefficients or click ‘No’ to cancel the import.
• Export: This option is used to export coefficients for selected active filters into a CSV file.
• Export All: This option is used to export all active filters in one go. Click on the “Export All” button, enter the path and file name, then click Ok. An XML file will be created which has coefficients for each active filter.
• Import All: This option is used to import all coefficients in one go. Click on the “Import All” button, enter the XML file path, and then click Ok. All the given coefficients will be imported and can be seen in the graph.
• Read:  This is used to read from the target to display in the panel.
• Tune:  This is used to apply a tune for the given value.

Configure Coefficients through Virtual prediction

1. On the MIMO Convolver tab, click on Measurement Coefficients. The Virtual Tuning window appears.
   
2. Click Apply after selecting Measurement session from the drop-down list.
   
3. Go to the Routing [in] tab.
4. Set the inputs for “Plugin Host” (such as Generator1 and Generator2). These inputs will determine the channels from the Plugin Host that will be used.
5. Set the inputs for “Mimo Convolver” in order to route the PluginHost output channels to the sound card outputs.
   Example 1: PluginHost1 and PluginHost2, if the output of Plugin Host is fed to MIMO Convolver.
   Example 2: Generator1 and Generator2, if generator is fed to MIMO Convolver.
   
6. Go to the Analyzer tab and select Plugin Host (MIMO convolver) output as the channel source.
7. Set the Channel source (such as Generator1, PluginHost1, and MimoConvolver1) to display in the chart.
8. Once the settings have been updated, click Done.
9. Connect to the device through Plugin Host. For more details, refer to Plugin Host Setting.
10. Open Channels, and assign channels to Graph A and Graph B.

A chart with Genertor1, PluginHost1, and MimoConvolver1 outputs appears.

In the advanced generator setting window you can configure different generator modes and set the various parameter of the signal.

• Sine: A single sine wave adjustable in the audible range between 20 Hz and 20 kHz by SineFreq. The phase between the two output channels can be set by SinePhase.
• DualSine: Two sine waves mixed together to one mono output. The frequencies can be set via DualSineFreq1 and DualSineFreq2, the mixing gains by DualSineGain1 and DualSineGain2.
• Square: Similar to the standard sine wave but shaped as a square wave.
• Noise: This is a stereo noise generator mode. In the Random mode, a regular noise signal is produced. However, when the Noise Mode is set to Pseudo, a multi-sine signal is generated where a sine wave is produced on each frequency bin of the chosen analyzer FFT. The phases of all the sine waves are distributed randomly to create a signal similar to noise.
  This mode is used for spectrum analysis of static transfer functions, and it is essential to set the analyzer window function to Rectangle for optimal results, producing very smooth spectrums.
  The NoiseColor can be changed between Pink (-3 dB per octave fall off) and White (flat frequency spectrum).
  By adjusting the phase, the output can be coded in a way so that surround upmixers can pan the signal according to the adjusted angle. The output changes from mono at 0° to L/R uncorrelated at 90° to out of phase at +/- 180°.
• Dirac (Dirac Pulse): In this mode one sample wide pulses are generated. The time between two pulses is set by SignalLength.
• SinePulse: This mode generates sine squared pulses. The shape of the pulse is set by SinePulseFreq, the interval between two pulses by SinePulseInterval.
• SineBurst: In this mode sine bursts are generated. The frequency is set by SineBurstFreq, the length of the burst by SineBurstLength, and the interval by SineBurstInterval.
• LinSweep: This generates a sine sweep starting from SweepStartFreq and ending at SweepEndFreq. The length of the sweep is set via SweepLength. The frequency progress is linear.
• ExpSweep: Similar to LinSweep only with an exponential frequency progress.
• File: Click on the folder and select the wav file. Based on their selection, the number of channels present in the WAV file will be displayed here. For the selected file, each channel of the selected file will be used as the generator input.
  After selecting this mode, the user has to adjust the routing settings, hence number of channels depends on the selected file.

After changing the mode from file mode to any other mode, this routing adjustment has to be adjusted according to the user need and will be signaled by GTT as shown below.

Use the “Active” checkbox to either select or deselect all traces. When you select the checkbox at the top, all instances in the window will be automatically selected. Similarly, when the top checkbox is deselected, it will unselect all the traces in the trace window.

Additional Configurations

Loop: If you enable the “Loop” option while using Dirac, SinePulse, SineBurst, LinSweep, ExpSweep, or File mode, the generator will play the chosen signal repeatedly when the Play button is pressed. However, if the loop option is disabled, the generator will play time-limited signals upon pressing the “Play” button.

Delay: You can enter the Delay value. The delay represents the time interval between the input and output of the generator, indicating the time it takes for the generated signal to propagate through the system.

Gain: You can enter the Gain value. The Gain setting allows you to increase or decrease the volume or strength of the generated signal.

The signal generator has a stereo output. This is relevant for signals with adjustable inter-channel phase or stereo wav file playback.

The Graph display setting enables you to customize the appearance and behaviour of a graph or chart. These settings allow you to control the visual aspects of the graph, Min/Max of various parameters, as well as the overall layout style.

Following are settings you can configure in the “Graph” display.

• Set the Minimum and Maximum value for the Time/ Frequency/ Amplitude/ Spectrum/ Magnitude/ Phase/ THD parameter.
• Interval sets the delta of horizontal/vertical labels.
• Set Frequency axis as Logarithmic or Linear.
• Set Phase display as Wrapped or Unwrapped.
• Set the curve line thickness for Measured Data Line, Traces Line, and Target Traces Line.

After updating the graph settings, click on Done to save the changes. Ensure that values persist when importing or exporting a project.

Interval will be disabled for Log Scale.

Audio signal routing refers to the process of directing audio signals from a source to one or multiple destinations within an audio system. In audio systems, signal routing can be achieved through different methods, depending on the complexity and requirements of the setup.

On the Routing tab, the connections to the sound-out devices, plugin host, mimo convolved, and file recorder can be set.

The Sound Out channels 1 to 16 correspond to the channel pairs found in the “Streams” section of the “Sound Card” settings. Click on a control in the “Sound Out” column brings up a context menu from which you can choose a source.

Currently, the player is not supported as a source.

The Analyzer channels (excluding Average channels) can be set as a source for the recorder to any Routing sinks. The recorded data should be the same as the analyzer data if the Analyzer is set as the source for the recorder.

Upon clicking “Routing Preview,” a use case overview will appear to enhance the understanding of Routing.

Saving RTA Settings

Once you complete all the RTA settings, click on the “Save” option. A file save dialog box will appear, enter the file name, and click Save.

Upon clicking “Save” within the dialog box, all of the following settings will be exported to a file with the. rta extension in a human-readable JSON format.

• Generator
• Analyzer
• Audio Driver
• Display

Loading RTA File

Upon clicking the “Load” button, a file open dialog box will be displayed. Locate the desired .rta file and click “Open” to restore the RTA settings stored in that file. The loaded settings will take effect immediately.

If the sound card settings are invalid when you load the settings, a settings window will be launched. You will need to fix the sound card settings issue before being able to proceed further.

Upon clicking the “Apply” button, the sound card settings will be applied. Subsequently, you can modify other settings according to your preferences.

After importing the settings, it is necessary to reconnect the device.

The Advanced settings window comprises of the following settings.

RTA Settings window is now non modal, you can save the settings and validate without closing It.

Related Topics

• Plugin Host Settings
• Advanced Analyzer Settings
• Advance Generator Settings
• Graph Display Settings
• Mimo Convolver Settings
• Recorder Settings
• Routing Settings

 

In the Channels setting window the numerical measurements are displayed for each channel.

The channel viewer list contains the following columns:

• The first column indicates the color of the channel. This allows you to change the color of the channel by clicking on the color box.
• Name: Display the name of the channel. You can change the name in the Analyzer Settings dialog box.
• Offset: +/- Db shifting of measured and math operated channels.
• Enable: Channel enable and disable allow on display graphs on Analyzer window.
• Peak: The peak amplitude of the current block of analyzed audio samples.
• Rms: The sound level meter value, the unit as set in the Analyzer Settings (dBFS, dBV, dBSPL) with selected Weighting (A B C D).
• Thd: Total harmonic distortion in percentage (%).
• Thd+N: Total harmonic distortion plus noise in percentage (%).
• Delay: This value is calculated if Analyzer mode is set to ‘Delay’. The delay measurement is done by cross correlation between a reference channel and a channel that contains the reference signal that went through a certain path (example: amp – speaker – microphone). The delay can be calculated using the position of the maximum within the correlation result.
• Peak Freq: The frequency of the maximum level in the measured spectrum in Hz.
• Graph: Radio buttons allow you to quickly select the graph that displays that channel

By using the Peak, Rms, Thd, Thd+N, Delay, and Peak-Frequency buttons, you can select which values to display in the list.

In addition to assigning individual channels to specific graphs, you can also perform bulk assignments. If no channels are selected, you can use the “Move all channels to A, B, or Both” button to move all channels, including calculated channels, to the desired graph.

If one or more channels are selected, the same buttons will only move the selected channels to the desired graph.

You can use the “Select All” and “Select None” buttons to check or uncheck all channels, respectively.

The selector control located at the top left of the window enables you to choose which group of channels to display in the list: all channels (Graph A & B), only Graph A channels or only Graph B channels.

The channel window is designed to remain on top of other windows and can be resized as needed, making it easy to keep open for value observation while using the RTA.
Click on the “Advanced Settings” to perform additional configuration. For more details about Advanced configuration, refer to the RTA Advanced Settings.

Math operation on Live Channels

To perform math operations:

1. Select any two channels.
2. Click on the Calculate button to get the math operation result.
   Math operated channel is listed on the same view.
   

You can delete Math operated channel and as a tooltip, you can find which channels are selected for math operations.

Only one Math operated channel can be created for combinations of measured channels.

Using an Analyzer, you can measure and analyze various aspects of an audio signal. It can be used to measure characteristics such as frequency response, amplitude, distortion, and noise level.

You can configure following features to measure and analyze various aspects of an audio signal.

• Banding –  For breaking a signal into a number of different frequency bands, and encodes each one independently.
• Mode – For selecting different analyzer modes.
• Advance Settings – For configuring advanced analyzer settings, for more details refer to Advance Analyzer Settings

Banding

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In Spectrum or Multiplexer mode, it is possible to adjust the “Banding”. When the banding is turned off, all frequency bins of the spectrum are displayed, allowing for a highly detailed analysis. However, this setting requires more CPU power as the amount of data that needs to be calculated and displayed increases with the FFT size.

Spectrum mode is shown in the example below when Banding is turned off.

On the other hand, when banding is turned “On”, frequency bins are grouped together. The width of each group can be adjusted by fractions of an octave, such as Oct12, which means that one band has the width of a 12th of one octave.

Spectrum mode is shown in the example below when Banding is turned on.

Mode

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Using the Mode option, you can select different analyzer modes from the drop-down list. The available modes are listed below.

• Time: Displays source channels in the time domain (one block of 4096 samples).
• Spectrum: Displays the spectrum of the source channels.
• Multiplexer: Switches the RTA into a multiplexer mode where multiple source channels are combined into two average channels.
• Phase: Displays the magnitude and phase of the source channels. Phase can be wrapped and unwrapped using Graph Settings in the settings window. The phase measurement is done by a dual-channel FFT analysis.
• Delay: Displays source channels in the time domain. The delay measurement is done by cross correlation between a reference channel and a channel that contains the reference signal that went through a certain path (example – amp – speaker – microphone). From the position of the maximum within the correlation result the delay can be calculated. The calculated Delay value is displayed in the Channel viewer in the Delay column.
• IR: Displays the magnitude and IR of the source channels. This is an Impulse response measurement with an exponential sine sweep. When this analyzer mode is selected ‘ExpSweep’
• Generator mode is set, and you are not allowed to change to other modes. The ‘Play’ button is disabled in the Generator view and with the ‘Single’ button he can generate ‘ExpSweep’ once.

Microphone setup tasks such as calibration, channel selection, and mic compensation file selection can be done using the Mic Setup view. If analyzer source is Sound-In, its respective calibration and compensation files will be considered for magnitude curve correction.

The compensation file is only considered for magnitude curve correction; it has no impact on calculated metrics such as sound pressure level (SPL) and total harmonic distortion (THD).

A signal generator is an important feature that generates specific measurement signals. These signals can be sent to the device or system for evaluation.
To conduct audio measurements, it is essential to have specific measurement signals that can be produced using a built-in signal generator. You can generate a signal using the “Generator” button in the ribbon bar.

By utilizing the “On/Off” function, you can activate or deactivate a signal. It is possible to generate multiple signals using this feature. The number of signals visible in the “Generator” window is determined by the number of instances specified in the Generator settings.

The gain of the generator signal can be adjusted in 1 dB steps with the Gain control.

To configure the signal, click on the “Generator Settings” to open the advanced RTA setting dialogue box. Here you can configure different generator modes.

On the RTA setting dialogue box, enter the instance value or use the increase and decrease buttons to change the instance value.

Using the “Mode” option, you can select different signals from the drop-down list. The available modes are listed below.
For more details about advance generator settings, refer to the Advance Generator Settings.