If you are using the y cable to connect your iphone 5 with the 30 pin lightening adapter to play music or pandora on your mini and have found you only get music coming out of one side of your speakers which I did and couldn't figure out why... I finally figured out how to correct it.
Go to your phone settings. Go to music. Turn on - Sound Check. This should fix the problem. This is for those of us who do not have mini connect but want the joy of listening to pandora via our iphone.