Comment 84 for bug 1553685

I have got the same problem too on Lenovo y720. Speakers sound so tinny, no deep bass at all, and the subwoofer does not works at all.
I don't know if it's of any help, but when I install Ubuntu in virtualbox, I suddenly have at least double the amount of audio settings, everything from subwoofer to deep audio, to bass, to high quality audio is working. Alsamixer also got lots of more settings.
In the virtualbox, the audio chip for some reason went from Realtek ALC233 (on native ubuntu), to Analog devices AD1980. The sound card went from just intel HDA on native ubuntu, to Intel 82801AA-ICH.

Follow my post with pics on askubuntu:
https://askubuntu.com/questions/1070640/ubuntu-drivers-in-virtual-machine-different-than-native-ubuntu