preconditions:

• author has limited english knowledge
• 27" imac i5, 11,1, late 2009
• linux mint 11 installed and running
• poor sound of the built-in speakers
• hint: i use linux mint 11 in the language german; so you have to adapt some software names (if i doesn't know them in english.

procedure:

• install gnome-alsa-mixer (i used synaptic)
• run gnome-alsa-mixer (you can start using the linux mint 11 menu, topic multimedia)
• check surround speaker in the lower left corner of the gnome-alsa-mixer window.
• adjust (to your needs): master, front sp and surround.

kind regards