well the first thing to shoot for is consistent tone, achieve this through long tones. also, what voicing do you use. i like the ee voicing and you want to try that

Unclear tone is due to lack of air support ( not what jazz guys call support that is different ) the support that lets one play with a very loose embouchure with hardly any lip over the bottom teeth. To practice this play with octave key D E F G and loosen the embouchure until it sound as if you are playing multiphonics ,,, The support that does not cause any change of color as you move up the scale. The support that permits octave jumps without any lipping the support that permits notes to move from one to the other without any holes . Any mouthpiece will do as long as it is decent s-90 or C* or Vand A17 or Rousseau or any well made mouthpiece with a med chamber ,,med table length ,,med opening ,,,with med reed,,, the rest is the indian not the arrow.