Here is Shakespeare's his definition of a true Christian leader and teacher.
This is the job description of someone who is truly called to lead the living Christian church.
The "imagined" voice refers to the preacher's voice having a divine tone of authority, grace and wisdom that creates an imaginary effect in congregations of hearing the very voice of God, Himself.
To note: the "Speaker" in the English Parliament is the person who presides, who has authority, judges correctly and fairly. He implements the rules and duties of members of the House of Commons:
"How deep you were in the Books of God.
To us, the Speaker in His Parliament;
To us, the imagined voice of God Himself;
The very opener and intelligencer
Between the grace - the sanctities of heaven,
And our dull workings."
Henry IV Part II iv.ii