Logitech Z-4 Computer Speakers "sub mean screen" Questions

...screen appear HD (I dont know what means) then my left speaker nothing action means no sound appear...when i pressed diagnostic button..everything goes well... Any solution on this... Your kindest ...

...sub is quiet. Any sugestions? Hello gameboy798, these are instructions to "Fix the Sound / Audio." Part1 From the "Desktop Screen." [Right / Alt] click on the Volume Icon. Once the 'window' ...