I don’t know since when, but for a while now I am seeing this behavior in my KDE 4.14 desktop that when I increase or decrease volume using KMix, volume in othet KDE applications also increases or decreasing correspondingly. Basically it means, there are no separate controls for KMix and other KDE applications.
Tried to search on web, and came across this KDE bug
where it explains this is called “flat volumes”. Some people may like this feature, but not me right now.
is how to disable flat volumes.
flat-volumes = no
in /etc/pulse/daemon.conf to disable this system wide or in ~/.config/pulse/daemon.conf to disable for the user.