I've made the connection from my IMAC to the TV but, it doesn't work. I do get the desktop to show on the TV but, nothing else. In addition to the hdmi cable I have an audio cable connected. What am I doing wrong?

I plan to connect my IMAC to my smart TV via hdmi cable with a mini DVI adapter but, when I ordered the cable the manufacturer states that the mini DVI port does not support audio. Is this true and if so, do I need a cable from the mic port to the TV?