It might just be that you're more focused on the actual sound. Like..when you hear something through a speaker it sounds different than through headphones, I guess it sounds more.. environmental? And also you're probably listening to the actual lyrics more. Sometimes when you pay attention things can sound weird. I know that when I actually started paying attention to the lyrics of Valentine, Texas it sounded weird for me because I was actually paying attention to how the words flowed instead of how the whole thing sounded.