Bare wire actually creates the best contact with the terminal because it avoids making additional connection points which can fail. This would have a negative effect on sound quality. I have had speaker wire oxidize on me in the past (jacket turned yellow) and I did not notice any difference in sound quality then the speaker wire I have now which is also even a higher gauge.

I’m armed and I’m drinking. You don’t want to listen to advice from me, amigo.

-Max Payne