I have Z680's hooked up to my xbox through a digital cable, and while
playing games no voice comes from the center speaker, only sound
effects.
Voices are really quite, and if anything is happening at the same time
someone is talking you can barely hear what they say, so I have to turn
it up really loud, and then explosions and things like that are even
louder.
This happens on all my games and DVDs, can anyone help me figure out why
this is happening?

If I plug my xbox into my TV and just use my TV speakers voice levels
are fine.
Same thing with gamecube I bought a Y adapter and hooked it up and some
thign swere loud and others were quiet.
Thanks for the replies in advance.