Kelly 51D vs Yamaha SL-48L-GP
The Kelly 51D has a wider cup diameter, the Kelly 51D features a deeper cup.
How deep the cup is, from shallow (brighter, easier high register) to deep (darker, fuller sound).
Mouthpiece A
Kelly 51D
• Trombone
ProfessionalCup depth
Best suited for
Orchestral playing — large cup for full, dark tone
Professional euphonium and trombone players
vs
Mouthpiece B
Yamaha SL-48L-GP
• Trombone
Cup depthMedium
Best suited for
High-volume projection — open throat for power
Cup Depth
The Kelly 51D has a — cup while the Yamaha SL-48L-GP has a medium cup. Deeper cups favor a darker, richer sound; shallower cups provide more brightness and easier upper register.
Which is better?
Neither mouthpiece clearly dominates the other — the right choice depends on your embouchure, playing style, and the sound you're after. Try both if possible.