Multi-Sub Optimizer Reference (page 7)
Adding Filters, Delays and Gains
Once you add filter channels, you can add filters, delays and gains to them. To do so, right-click on the Filters category node under the newly-created channel. This presents a context menu allowing the addition of various filter types (delays, gains and polarity inversions are considered "filters" for this purpose).
Restrictions on Filters, Delays and Gains
The available filters depend on whether the chosen channel is a main or sub channel, as well as what filters have already been added to that channel in certain specific cases. For instance, once a delay has been added to an individual subwoofer channel, another cannot be added to that same channel, as this would cause problems for the optimizer. If a delay or gain cannot be added, MSO shows the menu item as grayed out. For example, attempting to create the configuration of delays shown below in Figure 1 is disallowed.
This can be remedied in several ways. One way is shown in Figure 2 below.
The leftmost delays in each of figures 1 and 2 above represent delays added to the Shared Filters node under Subwoofer Channels in the Config View. If you try to add a fifth delay to the configuration of Figure 2 in an attempt to obtain the configuration of Figure 1, you will find that MSO has disabled the menu option to add the delay. Of course, any of the four channels in Figure 2 can be chosen as the one without a delay block.
Another permitted delay configuration is shown in Figure 3 below.
This configuration has no delay block under the Shared Filters node of Subwoofer Channels in the Config View. Allowing negative delays is permitted, and can be a useful technique if the delay implied by the AVR subwoofer distance setting used when the measurements were performed is larger than the optimum value.
An exactly analogous situation exists with gains as well. MSO prevents configurations that will cause the optimizer trouble, and the preferred configurations for sub gains are analogous to the delay configurations of figures 2 and 3 above.
Delays and Gains Not Allowed in Main Channels
Delays and gains cannot be added to main channels. It's assumed that mains distance and level trims have been set correctly prior to performing measurements. Relative gain and delay are accomplished using adjustments to subwoofer channels only. Reductions in delay of the sub channels relative to the as-measured condition are accomplished by allowing negative delay values. A negative delay means that the delay should be reduced relative to the as-measured condition, which corresponds to increasing the subwoofer distance setting in your AVR from what it was when the measurements were performed. These distance changes will be shown at the end of the filter report, which you can view after the optimization is run.