Here's the problem. I have dual speakers on my BenQ monitor. For as long as I can remember (i.e. since the day i bought this system 2 years ago), music has been playing from the two above mentioned speakers. I also have a headphone with an inbuilt mic, which I use for sound recording or DJing purposes on an online radio station.
About two days ago, sound suddenly stopped playing from my monitor's speakers, and instead started playing from my headphone.
I've checked the monitor's wire connections, and although I'm not sure if they're where they're supposed to be, I know that the connections are tight and secure.
Try taking disconnecting the headphone from the speaker. If the headphone was plug in the monitor drive, not the speaker. Unplug both headphone and speaker wire and plug the headphone in the old speaker spot, and the speaker in the old headphone spot.