[vinhboy]

I assume if his wifi can pick it up with wireshark, then whatever is receiving should be able to pick up whatever his wifi send out. Right?

[detaro]

Not necessarily, the speakers could be in a different network, then they do not listen to what he sends directly. if the AP/router knows the multicast source is not in the wifi (and it probably does) it won't accept packets from there and not forward it to other networks.

Since it is multicast seeing the packet doesn't mean the path to a specific receiver goes through your network.