Yup, i also realized this as well. On the 4S it seems like the trebe is maxxed out and the bass is completly turned off. I have an iphone 4 right next to me when comparing and the 4 sounded much more realistic with both trebe and bass at the right level.
Hope they can fix this.......... and yes it sounds perfect when listen to the song in the music app.
Hope they can fix this.......... and yes it sounds perfect when listen to the song in the music app.