First of all, I think the Right Channel is broken! To test it, I download this mp3 file, the sound start from left then go to right, you can find it here:
address: http://pan.baidu.com/s/1dDf4QK5 Pass: ibwa
if it tell you input a pass, then input the pass above!
Then, Sure! It's Mono! The External Speaker broadcasts all sound of both Channel!
And some more I should tell you is that, I root my Z1C following the guide:
Is there something wrong? Or the Z1C's External Speaker is just MONO?