A few years ago I added an external speaker to my FTM 350. It improved the performance of the radio. I was in the candy store yesterday and thought I would add another speaker for the other side of the cab of my truck as I remembered that the radio came with a one-to-two plug. I installed the second speaker, and only one makes noise. Is the one-to-two plug for some other purpose? How can I make both speakers work so the radio can be heard from both sides of the cab as the speakers on the back of the remote head really stink?