how do i turn on usb speaker on MacBook
How do I turn on the USB speakers plugged in to my MacBook Air
iPhone 4S
there really is no such thing as a pure usb speaker usb speakers are external audio cards with speakers connected
and require a device driver from the manufacture to work
Setting USB speakers as default audio output?
more
https://www.google.dk/search?q=mac+change+audio+to+usb+speaker&ie=&oe=