Recently I upgraded to the latest ZS620KL_WW_90.11.162.58 and the sound quality got even worse! It wasn't great to begin with, the Audio Wizard is perhaps the worst audio effects tool I've worked with.
I'm using Creative ONE Bluetooth headphones on the default headphones setting in the Audio Wizard and all I hear is overloaded bass! I tried different headphone profiles (what a terrible idea to add presets instead of an actual EQ! Why? Because my headphones are not there and thousands of others).
Is there any way to at least revert back the sound, I can't listen to my usual playlists because all I hear is overloads.