I can confirm from experience this degree of difference is quite audible. I have just set my speakers up with a laser level after having had a new floor installed. The floor under the right speaker was 4mm lower than the left speaker - increasing the spike height to level the setup made a clearly audible improvement.


Streaming: Roon, NUC, QNAP869 NAS
2ch system: dCS Vivaldi, Audionet Stern, Audionet Heisenberg, Magico Q1
Retro system: 101/104/105, Red Rose Spirit