<div id="mediaplayer"></div>
<script>
$("#mediaplayer").kendoMediaPlayer({
    autoPlay: true,
    media: { title: "Kendo UI for jQuery: Welcome and Overview", source: "https://www.youtube.com/watch?v=UbkbVBNYZMc" }
});

setTimeout(function () {
    // get a reference to the media player widget
    var mediaPlayer = $("#mediaplayer").data("kendoMediaPlayer");
    // check the current volume of the player
    mediaPlayer.volume();
    // sets the current volume to 50
    mediaPlayer.volume(50);
  }, 1000);
</script>