I'm using Audio MIDI Setup on my 27" iMac running Mavericks to ouput sound to 2 devices (both iMac speakers and a Big Jambox, a bluetooth speaker), it works but with some latency. I tried drif correction in Audio MIDI Setup but doesn't change a thing.
How can I output sound to multiple devices without the latency issue ? I'm pretty sure that's possible. Maybe with a 3rd party software?