Hi there! I'm a new user of Linux Mint Nadia and I had the same problem with Ubuntu before. I have a 5.1 Audio System and doesn't work all of them, only the 2 frontals speakers works. I have run "lspci" on terminal and the result is: 00:1b.0 Audio device: Intel Corporation 5 Series/3400 Series Chipset High Definition Audio (rev 06), I'm working with Pulse Audio but there is no way to make work all the 6 speakers, I've tried all the tricks that I found on Internet but none works. My motherboard is an Intel DH55TC.
Somebody have any ideas to solve that?