While I think you meant output some TVs have menus to enable speakers when the headphone is plugged in. This is not standardized so you have to check the manual and return TVs that don't do this.
I bought a SONY XBR65X810C 65" CLASS XBR (amazing purchase) a week ago and cannot figure out how to have a set of Turtle Beach X12 headphones hooked up directly to the the headphone input and thumb drive ports on the tv and still have sound coming through the tv speakers. This style of connection switches my tv to headphones only and mutes tv speaker sound. Basically I want the ability to have duplicate sound coming from my headphones (for me) as well as the tv speakers (for my wife). I live in an apartment so I don't want to invest in a surround sound system and be a terrible neighbor but want to continue having movie quality sound through my headphones and allow my wife to enjoy tv speakers while we watch stuff together because she doesn't mind that.
I've tried using the red and white sound connector inputs that came as a bolt-on option with the Turtle Beach headphones as well to connect my headphones as an external audio system (like I used to do with my older Sony Bravia 46") but that doesn't seem to be working here. I've tried both sound output choices through the tv display options (tv speakers/audio system speaker choices with both combinations of headphone connection) and I cannot seem to find a way to duplicate sound from the tv speakers AND my headphones simultaneously. Any advice??