Thanks for the pointers. I do have the sense that my next moves are fine tuning speaker and listening position placement, targeted treatments, and subs.
A problem for me, or maybe just a hang up, is wanting to know what to expect with each change before throwing more money at it. I’ve already spent too much without a good plan. I have the least confidence in knowing what to expect of treatments.
As I should have expected, DSP.edu doesn’t start with DSP. It starts with reasons why we have DSP in the tool box.
Specifically I only got to minimum phase before getting hung up. Sounds important.
It’ll take more foundational knowledge and more than one read through to digest but REW Help - Minimum Phase discussion
https://www.roomeqwizard.com/help/help_en-GB/html/minimumphase.html is a lot of help and as good a place to start as any.
Thanks also for the MATHAUDIO recommendation HAL. It looks like a promising add on to Foobar which I have already to play with DSD.