I'm not sure why you are wondering whether you are imagining that it sounds different from your old phone. Its likely to be a different design, made to different standards, with different components and software. If you hear a difference there is one, whatever the reason. Are you certain that it actually sounds worse and not just different? Sometimes when a track you've played hundreds of times before sounds just a little bit different if seems like a fault rather than just different. Try some music that you're less familiar with.