I recently upgraded with a fresh install Ubuntu 12.04 on my HP DV7-6135dx w/ Beats Audio.
The DV7 has 4 speaker and one Sub-woofer. Currently only two speakers are working.
Previously with 11.10 I fixed the problem by adding the line "options snd-hda-intel model=ref" to this file, "/etc/modprobe.d/alsa-base.conf" and then I would restart the PC.
When I attempted to use this fix with 12.04 I get no sound at all.