usb does not carry audio anything in terms of audio act the role of being an usb audio card and that mean one needs drivers
if Ultranova does not making working osx 10.9.X drivers the your usb audio card will not function
go to their site and see if they support your operating system
The Ultranova has an audiocard in it with 2 speakers connected as well. It works fine on my MBP which has the same software version as my iMac, but still doesn't work.
I've downloaded the driver for the Ultranova and everything should work fine, so I'm just lost.