I just installed a USB speaker that lsusb identifies as a GEMBIRD Honk HK-5002 USB Speaker.

It’s plug-and-play, and it works — not a great sound quality for music, but this is not what I want to use it for — save that the sound is either too loud (crackling and distorted) or, as soon as I try to lower the volume, it is muted.

I did some research and found the solution.

As sudo, open /usr/share/pulseaudio/alsa-mixer/paths/analog-output.conf.common to edit this section:

[Element PCM]
switch = mute
volume = merge
override-map.1 = all 
override-map.2 = all-left,all-right

Change the Volume value to ignore, and add a volume-limit, like this:

Element PCM]
switch = mute
volume = ignore 
volume-limit = 0.01
override-map.1 = all 
override-map.2 = all-left,all-right

You can change the volume-limit value to your liking, see the orginal post for more info on that subject.

Type pulseaudio -k to restart pulseaudio and, I hope so, enjoy your sound volume control working as expected.