Animator: Change at runtime speed of animation clip in specific Layer

Unity Engine
1

How to change the speed of an animation clip. within a specific layer.
After hours of research and testing.

AnimatorController ac= animatorruntimeAnimatorController as AnimatorController;
ac.layers [1].stateMachine.defaultState.speed = 3f;
2

The documentation of my Animancer plugin has an explanation of how to change the speed at runtime to compare it with Mecanim (scroll down a bit for the runtime part).