Getting error like this all the time are so annoying
ALSA lib pcm.c:2211:(snd_pcm_open_noupdate) Unknown PCM dmix:NVidia
if you have compiled alsa from source and can see the volume control, etc, but still speaker-test is showing all of the weird errors about device not found, or unkown PCM then it is probably the ~/.asoundrc file
The file will have a line that points by default to ~/asoundrc.asoundconf comment this line, and you should have your speakers back to life :)