Multi-Sub Optimizer Reference Manual (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.

Example of Disallowed Delay Configuration
Figure 1. Example of Disallowed Delay Configuration

This can be remedied in several ways. One way is shown in Figure 2 below.

An Alternative to the Configuration of Figure 1
Figure 2. An Alternative to the Configuration of Figure 1

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.

Another Alternative to the Configuration of Figure 1
Figure 3. Another Alternative to the Configuration of Figure 1

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.

Additional Delay Restrictions for Sub-Only Configurations

For sub-only configurations, only the relative delays between subs are meaningful. Any delay configuration such as Figures 2 or 3 above implies a shared or common delay among all subs. But such a shared delay does not affect integration of the subs with one another at all. A shared delay is only useful for integration of subs with main speakers. With "sub plus mains" configurations, such a shared delay models the sub distance setting of the AVR or preamp/processor. Allowing such a shared delay for sub-only configurations would cause convergence problems for the optimizer, so they are disallowed. Therefore, for sub-only configurations containing N individually controlled subs, only N - 1 delays are permitted, as shown in Figure 4 below.

Legal Delays for Sub-Only Configurations
Figure 4. Legal Delays for Sub-Only Configurations

For sub-only configurations, it's necessary to figure out which sub channel should end up with no delay block. Instructions for doing this can be found in "Normalizing Gains and Delays" in the "Tips and Tricks" section.

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.