Filter Panel

The Filter Panel provides controls for the Speaker Type, Bass Management Cutoff and filters for each of nine channels, which by default are titled Left, Right, Centre, SL, SR, SBL, SBR, Sub and Aux. Channels can be selected from the keyboard using Alt+number, 1 for the Left channel, 2 for the right etc. The text on the channel's tab is black if the channel has measurement data, grey if not. Above the channel selection tabs are buttons to set the Target Level and to control the process of locating peaks and assigning and optimising filters to correct them. The currently selected equaliser is shown at the top of the list of filters.

The channel names can be changed by right-clicking on the channel's tab, the new name is remembered for the next startup. There is an option to reset all the channel names to their defaults (Left, Right etc). The right-click menu also has a shortcut to the dialog for viewing/editing the measurement notes (for more information see the View menu entry).

Filter panel channel tab

Channels for which measurement notes have been entered show the notes icon on the tab. The notes themselves appear in the tooltip text for the corresponding tab.

Measurement Notes in Tool Tip Text

Set Target Level

The Set Target Level button button is used to measure the SPL the current channel produces when fed with a pink noise calibration signal at the Measurement Level. The resulting SPL then becomes the target level for the channel for subsequent filter adjustments. When the button is pressed a reminder window is displayed confirming the connections required, when OK is selected the Wizard first checks that the level from the SPL meter is suitably low when there is no signal, then generates the calibration signal and measures its level. The Target Level control in the Filter Panel is then set to the measured level.

The Target Level that has been measured for a channel remains valid as long as the SPL Meter is not moved and the AV processor volume, input level and measurement level are not altered. If any of these have changed, or if the channel is being re-measured with additional EQ filters or modified EQ filter settings, repeat the Target Level setting for the channel before making further measurements.

Find Peaks

Find Peaks button  Search for peaks in the measured data for this channel within the frequency range set by the controls below the button. Results are shown to the left of the graph, sorted by the amplitude of the peaks relative to the channel's target level. The peak data can be hidden/revealed via an item in the Graph menu or by using the corresponding shortcut keys.

Assign Filters

Assign Filters button  Assigns PK filters to correct peaks found by the Find Peaks function. Filters are assigned in order until either all peaks have been assigned a filter or all available filters have been used. Only filters with "Control" set to "Automatic" are used.

Optimise PK Gain and Q

Aptimise PK Gain and Q button  Iteratively adjust the gain and Q settings of the PK filters to obtain the best match to the shape of the peaks and hence the flattest corrected response. The optimiser tries to match the shape over a region either side of each peak's center whose boundaries are determined by the characteristics of the peak and the nature of the frequency response nearby. The matching of filter to peak is easiest to see when the Invert Filters box is selected.

Adjust PK Gains

Adjust Peak Gains button  This button adjusts the gains of all Automatic PK filters to bring the response at their centre frequencies to the target level. Q is not altered. The main use for this is to readjust gains after making some manual adjustments to the filter settings.

Speaker Type

Speaker Type selector  The Speaker Type for each channel can be set to "Bass Limited" (often referred to as "Small"), "Full Range" (often referred to as "Large"), "Subwoofer" (strictly speaking only applicable for the Sub channel) and "None". The setting is remembered for the next startup.

The Target Response shown on the Graph Panel reflects the Speaker Type, with a 12dB/octave high pass shape for Bass Limited speakers, flat for Full Range and a 24dB/octave low pass shape for Subwoofers.

Bass Management Cutoff Frequency

Cutoff Frequency selector  Bass Limited speakers and the subwoofer have an associated Bass Management Cutoff frequency. The default is 80Hz, frequencies from 30Hz to 150Hz in 10Hz steps are allowed. The setting is remembered for the next startup.

Target Level

Target Level control  The Target Level for a channel is the SPL the channel's speaker would ideally generate when fed a signal at the Measurement Level. This level is used to offset the Target Response correspondingly. The Wizard sets the Target Level for each channel, though it can be manually adjusted if required.

Trace Offset

Trace Offset control  The Trace Offset control for each channel allows the position of the channel's frequency response traces to be shifted. This only affects the position of the trace on the graph, not the actual data values. To change the data values for a trace by the offset amount (which is in dB), use the Add to Data button. Note that re-generating the frequency response from the impulse response using Apply Windows will cause the levels to revert to their original values, to re-scale the impulse response for a desired peak SPL figure in the frequency response use the Scale Impulse Response controls in the Impulse Response Controls graph group.

Filter Controls

Filter Controls

Each filter has:

The DSP1124P mode has an additional display showing frequency in the form in which is must be entered on that unit, i.e. as a one-third octave centre and a fine adjustment which ranges from -9 to +10.
BFD Pro Filter Controls

The Filters and Filters+Target traces in the graph area update as filter controls are adjusted.

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