Your HTC One M9 comes with HTC's Boomsound. The phone has 2 front-facing speakers with a built in amplifier to deliver the rich audio you get from Boomsound with Dolby audio. The new Boomsound comes with support for 5.1 channel surround sound for your built-in speakers or for connected devices (HTC BoomSound with Dolby Audio is not available over HDMI, Bluetooth,Miracast, or USB audio out). According to HTC, "listeners can perceive more details in a rich and pleasant audio space whether its from the smartphone speakers or headsets." When you are listening to Music, use Boomsound Music mode. You will get a little more out of your bass with music mode. However, when you are watching a movie, switch it to Theatre Mode. It will sound a bit louder and accentuate the audio effects of the movie.
To change the setting while in your movie or song, drag down the notification bar. Choose Switch mode to toggle between Music mode and Theatre mode.
Use the headphones that came with your HTC one and you can choose the in-ear option to get the best experience out of your headphones. Boomsound makes audio on your HTC One M9 a truly unique experience for your ears. I am impressed with the sound quality on this phone.
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