New USB speakers don't respond to Output volume settings.

[kj]

Kind of like Gareth is saying, I bet the digital info is being sent straight to the speakers, and the speakers basically have an audio interface built in. So the volume has to be set on the speakers. Or now that I think about it, perhaps they don't use Core Audio? Do you have to install a driver for the speakers? Is there one available? Idk, just thinking out loud.

Edit: there do seem to be audio devices that are not, or are not fully, core audio compliant. That could be the prob.