The Yin & Yang of masterful speaking.
Power is an outgoing energy. Engagement is an ingoing energy. Our voice is an instrument of power; it sends sound waves out to our listeners. Our eyes and ears are instruments of engagement; they take light and sound waves in from our listeners.
Most of us understand "public speaking" as being all outward. We are told to PROJECT our voice (the right idea). We are also told to fake engagement by POINTING our eyes AT people (the wrong idea).
Masterful speaking requires an openness and vulnerability to our listeners. When balanced and mixed with power, this engagement allows both listener and speaker to be changed and to grow.