5D II audio monitoring w iPhone 4-pin adaptor?

[Meca]

Hello,
Trying to monitor audio w a 5D II, using a 3.5mm socket to 4-pin pole jack plug adaptor. The cable is sold as a mic adaptor for iPhone etc., but seems to have the correct TRRS set up. As such audio goes only to the left headphone Am I in error trying this solution? Should I just get the sescom cable or is there anything in ML I can try? (Using latest ML builds & Canon firmware)

Apologies if posted before, I did have a look on the forum. Your assistance is *very* much appreciated. 

http://www.magiclantern.fm/forum/index.php?topic=2880.0
http://www.micronic.co.uk/store/item/1053/standard-3.5mm-microphone-adapter-for-ipad-ipod-iphone-works-on-video-audio-app