How to Reset all Sound Settings in Series 6 4K UHD TV(KU6470)?

It will Reset all Sound settings to their factory defaults and will remove all the changes that you have made.  

Press Home Button on Samsung Smart Control → Settings → Sound → Expert Settings → Reset Sound → Yes  

Pictorial representation to Reset all Sound Settings in your TV is as follows:

a). Press the Home Button on your Samsung Smart Control, to access the Home Screen.

b). Using the Directional pad on your remote, navigate to and select Settings.

c). Select Sound.

d). Select Expert Settings.

e). Using the Down Directional button, scroll down the list until you reach Reset Sound.

f). Select Reset Sound.

g). Select Yes to reset your sound settings.