Oukitel k12 sound quality low

Hi there,

I recently bought brand new Oukitel k12 from your store in Hong Kong, the phone is super excellent except the sound quality is really low! I turn on the volume to maximum, also I checked the sound setting it's turn to maximum as well, when I play music or a video the sound from the speaker is low! also if I use earphone/headphone the the sound quality still low! I'm wondering why is that! my old phone speaker quality is really loud!