IMAY I tried everything as you wrote. center speaker, turned off the subwoofer, then soon 028=01 nothing at all on that setting. then 028=04 there was a weak sound on that setting. but the volume on the ihu was at high max. balancer and fader in all positions. without change. despair.
normal sound on channels 1 and 3.
2.4.5. quiet weak
normal sound on channels 1 and 3.
2.4.5. quiet weak