There's definitely a cadence behind how televangelists speak. But if you were to listen to one broadcasting in say Minnesota, I don't think you'd hear the Southerness to the speech if the evangelist was a native.
Prayer voice is something I struggle with intellectually. On the one hand it's good to have a voice distinct from our normal speech that helps set prayer apart from normal speech. We should be addressing God differently than we address other human beings. On the other hand though, I find the prayer voice to be somewhat creepy now that I'm older. I find while I don't want to use phrases or terms that infer a sort of buddy familiarity with God, I do feel like we should talk to God the way we might address a loving parent. Submissive, friendly, and some other adjectives I can't find words for. The way we teach kids to speak when praying though sounds wrong to me.