Dell laptop Audio problem with headphones

Hi there,
I have an Dell XPS 11 Laptop which has this issue on audio output when I connect it to Head phones(or subwoofer), when I insert the jack plug, audio continues to play from internal speakers, when i set the headphones to be default, audio plays from internal speakers and when I plug headphones they can play fine, but when I try playing audio from YouTube, it plays through internal speakers even with the Headphones plugged in, what could be the problem ? How do I fix this?
