mrlowbrass

Double buzz is from your lips being too hard or too far apart. When you play loud, the tendency is for your body to get tense and that will obviously cause your embouchure to get too hard. Also, when you are moving a lot of air, your lips will have the tendency to blow apart, causing two different buzzes from each of your lips, hence the term "double buzz." When you play loud, keep your lips relaxed and close together. It'll solve all of your problems with the Double Buzz.