My headphones volume is more than just good. Do you use bluetooth headphones
or aux? Because I've noticed that the sound gets worse when using blutooth.
And also you can try an app that I use, to boost the bass. But you can also increase the volume with it etc. The app is called Bass booster which is free on play store. But there's also a pro version. (I use pro)
But unfortunately I can't post the links since I just signed up to xda.
Sent from my GT-I9105P