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

Not including actual system components as such, but replacing my wood, then steel turntable stand with concrete blocks. Literally grounded, anchored, and solidified everything in my main analog only system.

Other than components, the things that made the biggest difference were:

Townshend podiums

Quality power cables

Using a laser measuring device to set the distance/angle of my speakers

Gary

Without a doubt, joining this forum and ending up with this

Sound wise:

Besides speakers and components - Went from spikes in cups on a raised wood floor to Herbie’s Threaded Stud Gliders. stopped random room resonance and cleaned up the bass.

Use:

Moved system out of basement quasi cave to den. I listen every day now.

Detached house. Able to play whenever I wan't. Well if the Mrs don't mind :)