Updating isn't real easy, nowadays the best way is just to wait until your distro releases a new version kernel. In the old days when alsa was not included in the kernel yet, most distro's had binary packages of those modules. I don't know (or think) that these still exist.
Of course if you want it now, there is another way. You'll have to have your kernel source (the version you're currently running), then go to
http://www.alsa-project.org and check out the docs. Alsa drivers are really well documented so you shouldn't have problems.
If you intend to do compile the thing, you should be sure that it will solve your problem, because it can cause many more. So, maybe look first if this bass output problem can't be solved by some setting.
good luck,
Elluva
