Janeen

I just bought a RSB-11 soundbar/subwoofer. I can't get sound out of it at all. Got it connected to HDMI-ARC on the TV. That's plugged into the TV input on the soundbar. CEC on the TV is turned on. On the soundbar I did the hold-two-buttons for a few seconds to turn CEC on. And here's my silly question: is the Digital Optical cable required? Is that my problem? If so, I'll have to had back across town to Best Buy to get one. Thanks in advance for your answers!