Search the internet for the pinout on the Bose sub. I don’t know where you would find a DIN to RCA adapter, but it appears to be what is needed.

Since this is a Bose issue and not a Sono issue, searching a Bose community would probably get better results. 

With some Bose systems the subwoofers is also the amp, connected to the small speakers with a specific for Bose connector. Could this be the case with your set up? Can you post some pictures?

Thanks 106rallye - you might be correct as the Jewel Cube speakers connect to the sub-woofer and not to the Bose amp/radio/CD player/Aux unit - perhaps you can tell from these pictures?

I do not see this will work. The Bose is not just a sub.

Unfortunately, you are right I suspect - that is what Bose told me...