So you want to watch a YouTube video on your phone and send audio to the Ray, rather than play the YouTube video on your TV?  I’m puzzled.

Yes. Only sound form YouTube or Neflix samsung app played on Ray. 

Terę is no problem with that on Iphones.

Don’t think there is a way from an android phone. iPhones can use Airplay I think but there is nothing like this for android

You might be able to use a Chromecast HDMI dongle to play to the TV and hence to the Ray.  Or possibly screen mirror your phone using a Miracast app.  That would depend on the capabilities of your TV, and I am not sure what audio quality you would get.