Among vivo X series, the initial ones were powered by MTK SoC. However, vivo X5 Max is powered by Qualcomm new SoC msm8939, which is also called Snapdragon 615. MSM8939 is upgraded from Snapdragon 400 series, different from Snapdragon 600 and Snapdragon 800. Previous call quality reviews which are mainly based on Qualcomm snapdragon 800 architecture. Today, we will have a look at call quality of vivo X5 Max.