Multi-Sub Optimizer Tutorial (page 7)

A Second Look at Graphs

You can demonstrate the tuning feature by making another graph. From the main menu, choose Graph, New Graph. Under the Data category, choose Filter Channels. The five filter channels you defined now appear in the list. However, only one of them, Sub Channel 1, has any filters in it. Check the checkbox of only Sub Channel 1 from the list as shown below.

Choosing filter channels to plot
Figure 11. Choosing filter channels to plot

Press Apply. Under Format, General, change the graph title from SPL vs. Frequency to Sub Channel 1 Response vs. Frequency. Under Format, Axes, disable autoscaling of the left y axis and enter -20 for its lower limit and 20 for its upper limit. Press Apply. The frequency response of Sub Channel 1 is shown, but it's just a flat line because the PEQ boost is set to its initial value of 0 dB. If the properties of the parametric EQ FL1 are not shown in the properties window, go to the Config View and select FL1:Parametric EQ. In the Properties window, locate the Boost (dB) parameter and click the mouse on the right column of the Value field. The spin control should appear as in Figure 9 above. Press and hold the left mouse button down with the mouse cursor over the down arrow of the spin control while observing the graph. You might have to wait a few seconds because the initial changes happen slowly, but you should see the filter response of the graph change as you tune the Boost (dB) parameter. When it has reached its minimum value of -15 dB, the graph should look as below. This assumes the center frequency and Q of FL1 are set to their default values of 80 Hz and 2.0 respectively.

Parametric EQ response vs. frequency with 15 dB cut
Figure 12. Parametric EQ response vs. frequency with 15 dB cut

For now, set FL1 back to 0 dB boost. To do this, just enter the text into the right column of the Value field of the Boost (dB) parameter. You must press Enter for the change to be finalized. When the change takes effect, the text display of the value turns to bold. The graph of the response of Sub Channel 1 should once again be a flat line at 0 dB.

Assume that each of the four sub channels will contain the following filters:

The channel for the main speakers will have no filters, delays or gain blocks of any kind.

Add filters to each of the four sub channels you've defined so its configuration matches the list above. For each sub channel, add the PEQs first, then the low-pass filter, then the delay, then the gain block, beginning with Sub Channel 1. Then move on to the next sub channel. Performing the steps in that order will ensure that the reference designators (e.g. FL1, FL2 etc.) match up with the illustrations in this document. The 24 dB/oct Linkwitz-Riley low-pass filter is added using the Advanced sub-menu of the context menu for adding filters and is named “LPF Linkwitz-Riley 24 dB/oct” . If you accidentally add the wrong type of filter, just select it and press the Delete key to remove it.

For Users With Conventional Home Theater Setups

It's worth emphasizing that this tutorial uses data from a user whose intent was to implement a variant of the Geddes method for multiple subwoofer integration. This was described earlier in "A Note About The Project". The example should therefore be considered an unusual case of a type not usually implemented by people with conventional home theater setups. Except in such unusual cases, people with conventional home theater setups should not add a low-pass filter to each sub channel in MSO as mentioned above. This project is specific to the original user, Jag768, who provided the data. The vast majority of users will only add gain, delay and PEQ blocks to each individual sub channel, not a low-pass filter, as this low-pass filter is already provided by the AVR's crossover network.

Saving Your Work

Now would be a good time to save what you've done. Choose File, Save from the main menu or press Ctrl+S. Navigate to the tutorial's Project folder and save your file as tutorial_1. MSO will automatically add a .msop extension to the file. A file with a .msop extension is an MSO project.