You can easily adjust the volume to your choosing while setting your alarm on the Horizon 2. When setting your alarm, choose the Alarm Bell 1 or the Alarm Bell 2 on the top of the speaker. As you go through your settings when choosing an alarm time, it will give you the option to adjust the volume setting you wish to have on the alarm. Just simply adjust the volume by turning the volume knob on the top of the speaker. After you choose the volume, press the volume knob once to move to the next settings option. 
Please note: the alarm volume will gradually increase until you choose to either snooze or turn the alarm off completely.