I just bought a 1963 Conn Victor 22B. It came with a Bach 3C mouthpiece which gives the horn a full, darkesh sound, so I'm making a switch from using my Rudy Muck 17C for this horn. It plays beautifully but low Eb, D, and Db, washes out when I play a chromatic scale up and down. I guess it's worse on the way down. It's like air has just come out of a tire. I'm pretty sure it's not my breathing because the low C played after those notes is full and rich............help!