Normally, use the left front speaker as your reference. Once you set it to what volume you want, i.e., 75db on your meter, then adjust the trim of each of the other speakers to match the 75db mark. Do NOT use the volume control except for on the front left channel. When you have gone through the volume trim on each channel, and they all match at 75db, then you are set. You can also use a higher or lower reference level than 75db.