I got a nice pair of Logitech Z-5 speakers for my apartment at the university but directly stuggled with volume control. It was somewhat working, but only in the range from 90-100%, 90 being whisper quiet and 93 being rock concert loud.
I found an easy workaround:
Open the file /etc/pulse/default.pa as root:
gksu gedit /etc/pulse/default.pa
Search for the entry “load-module module-udev-detect” and change it to
load-module module-udev-detect ignore_dB=1
Kill pulseaudio (but plug out the speakers beforehand as they are at max volume after)
You should now be able to control the volume of the speakers with the remote that comes bundled.
In the panel, the sound widget will not show the right volume.
The computer switches automatically between the laptop and logitech speakers if you plug them in the usb.
More information: https://wiki.ubuntu.com/DebuggingSoundProblems/KarmicCaveats#Volume