but very little indication of how to assess a room and what to do about it once one does
I have only seen one reference on how to assess and that involved an A/V consultant with expensive equipment. Actually, you can probably get a good idea of what is happening in your room with bass using an SPL meter and REW, and there are inexpensive mikes that will measure from 30Hz-8kHz, but I suspect measuring higher frequencies would be quite a challenge.
There is lots of info on what to do to treat specific issues.
