[emre]

I have the Harman Kardon sound system and I am having the same problem.
When playing spotify via wireless carplay, volume is remarkably lower compared to radio and saved music collection.

And yes, if I turn up the volume in carplay mode and then switch to radio or saved music it is too loud for me.

I don't like to play music loud in car. I keep the volume around 40% when listening to radio. If I switch to carplay I need to turn up the volume to around 60% and when I switch back to radio 60% is too loud for my taste and I have to turn it down.