I have a 5.1 speaker system, but on both SUSE 9.3 and Ubuntu 5.04, only the front right and left speakers and the subwoofer are working. I'm not getting any sound out of the two rear speakers or the centre speaker.

I've opened alsamixer and tried unmuting things and raising volumes, to no avail. (Curiously, the only parameters that seem to make any difference at all are PCM, Surround, and Duplicate Front, each of which has the effect of muting everything if I turn them off. So for example, Master doesn't affect anything, which seems strange...)

Does anyone have any suggestions? I'm really confused about this....

It utterly depends on your Sound Card. Mine works on all my systems. Be sure that in alsamixer "wave center" "wave surround" "center" "PCM" and "surround" chanels are enabled but all "LFE" chanels are disabled. LFE is to emulate matrix of 5.1 on 4 speaker systems

Thanks for the tip about LFE -- I didn't know what that was for!

As for wave center and wave surround, I don't see those parameters. I'm using alsamixer v.1.0.8. What do they do?

open terminal first!
$su
[root passwd]
#alsamixer
Configure bars with arrows, enable or disable service with "m" key.
When done ESC
#alsactl store

If you have 5.1 speaker system, be sure that LFE channels bars
are all way down and [off]. LFE channel is to generate 5.1 emulation
matrix on 4 speaker systems.


P.S. LOGOUT IS NEEDED!

I opened a terminal, and typed alsamixer, but I don't see "Wave Surround" or "Wave Center" anywhere.

I did turn down and mute the LFE bar, and restarted the machine, but I'm still not getting any sound out of my rear or center speakers.

I really appreciate your suggestions, but I can't get them to work for me. I'm still a newbie, so maybe that has something to do with it....

What card is that? If onboard AC97 that comes with NVIDIA and VIA chipset then it's 5.1 emulation for Microsoft only with lower channels passing through mike. In linux it won't work. If it's solid stand alone 5.1 card then operation I described above must work.
Also on SuSE there is a different way of doing this stuff:
Menu=>YaST=>Hardware=>Sound=>Volume
Adjust channels accordingly.
Again if you do not see the surround there it means that your 5.1 is emulation for Windows only. Sorry

The soundcard is integrated with my motherboard. I just opened alsamixer and it says that the card is NVidia CK804. I guess that means it's only "emulated" surround sound for Windows?

What does it mean for something to be "solid stand alone 5.1"? Are you talking about a separate sound card i.e. one that's not integrated with my motherboard?

Precisely! Hardware, not software. I also have NVIDIA chipset with integrated 5.1 onboard which works only for M$. I bought SB Live 5.1 and it works on all distributions. Even on BSD systems!
G'luck!

So I need to buy a new card?

Well, thanks very much for your help!

EDIT: By the way, how do you know this about the onboard surround sound not working on Linux? I've never seen a reference to that before....

I updated my suse to 10 and lost the sound as well.
I followed this:

and it worked.

Thanks