HTC One is equipped with Beats Audio speakers and you don't need to use headphones to enjoy the magnificent sound. Enable Beats Audio on HTC One and listen to music or watch movie, and see the difference.
To disable or enable beats Audio do as follows:
1. Open "Settings" App (Drag down notification bar)
2. Scroll down and find "Beats Audio" under "Phone" section
3. Tap it to turn on Beats Audio (Tap again to turn it off)