Originally Posted by Onetrack97
In general, when trying to integrate mains with subs, should I have a shared PEQ, Gain, & Delay, plus your suggestions from above?
Let's back up a little bit.
Your data showed the need for boosting the shared gain (AVR trim) by about 10 dB. This indicates the sub level was about 10 dB low during measurement. This means that when using all the gain blocks on a per-sub basis without a shared gain block, you need a fairly wide adjustment range for each per-sub gain block. This in turn can lead to wide differences between individual sub levels. If instead you use a shared gain block to do the "heavy lifting" of a large gain adjustment, you can then reduce the adjustment range of the individual sub gain blocks and more easily constrain the relative levels of the subs with respect to one another. The downside is that you're stuck with figuring out which sub should have no gain block in its path (there must be one, as you have a maximum of 3 gain blocks total allowed when you have 3 subs).
There's an analogous case with delays that applies to the non-HD miniDSP 2x4 units that's worth mentioning, even though you're not using one. These earlier units have a maximum delay of 7.5 msec, which is pretty limited. Often, a much larger delay adjustment range is needed. In that case, one would use a shared delay block in MSO with a wide range, including negative delay, implemented physically by the AVR in the guise of its sub distance setting. The AVR would then do the "heavy lifting" of a large overall delay adjustment if needed, while the non-HD 2x4 would make small individual delay adjustments. This setup also has the analogous problem of requiring one to figure out which sub should have no delay block (because there is a maximum of 3 delay blocks when 3 subs are used).
In your case though, the 2x4 HD has boatloads of delay range, so this problem doesn't come up. You can use an individual delay for each sub without a shared delay. I'd recommend allowing each delay to be negative on the minimum side of its range. If any negative delays do show up, they will be lumped into the AVR distance adjustment. A negative shared delay means "increase the sub distance relative to the as-measured condition".
1) Use a shared gain block to do the large sub gain adjustment as needed, with two individual sub gain blocks having a smaller adjustment range than the shared one.
2) For delays, use individual delay blocks for each sub, say -15 msec to +15 msec. The filter report will lump all negative delay into a sub distance increase if needed, while making the final per-sub delays positive or zero.
Shared PEQ are usually used when one wishes to get the MLP by itself as flat as possible as a final cleanup step per figure 42 of the tutorial
. If you do use shared PEQ, it should be as a final step after using individual PEQ to optimize multiple listening positions. Shared PEQ can't reduce the seat-to-seat variation of frequency response, but individual per-sub PEQ can.