Even with all bass off with full mid and treble the voice is still muffled compared to radio ect, but even this is not great
@Freebird: Thank you for your comment. I do not agree with it, but that's just how it is. If you want a solution I assume you have contacted Amazon HELP services who can give you real time solutions and can take over your account to check settings and stuff.
Actually, re-reading your post I am not sure what you need/want solved. Perhaps refine so that fellow customers (this is a Customer-2-Customer HELP forum) can help you :)
Good luck :) Cw
Edit: What voice? Music? Audible? Talk To Me? Briefing? Specific App?