What one change to your room, system, or setup made the biggest improvement?

Acoustic treatments, first, the first reflection point did so much for mids and treble and imaging, but then years later I moved some panels and soffit traps to block perpendicular walls to attenuate boundary interference, and THAT was what ultimately solved my 25 year problem with bass in a 23.5 x 20 ft room. It wasn't modes at all, it was the cancellation of multiple freq in the bass region from BI. Second best effect was moving 2 subs away from the mains and out into the room but at the sides. Third was a combined ground system, Synergistic Research plus Puritan Ground Master. The combination created a balance that neither alone could.

To the OP - room is the biggest factor in the system 

Going from mp3 to Tidal.  Brought tears to my eyes.

Love the the dummies cuz they solve all the world's problems. Research is comming out a couple treatments with led may help psychiatric problems.guess those guys in the 60s were on to something.enjoy the music and experiments.

Gummies now that I got rid of ai