Bach 17D vs Kelly 51D-EU
The Kelly 51D-EU has a wider cup diameter, the Kelly 51D-EU features a deeper cup.
How deep the cup is, from shallow (brighter, easier high register) to deep (darker, fuller sound).
Mouthpiece A
Bach 17D
• Baritone / Euphonium
Cup depthShallow
Best suited for
High-volume projection — open throat for power
vs
Mouthpiece B
Kelly 51D-EU
• Baritone / Euphonium
ProfessionalCup depth
Best suited for
Orchestral playing — large cup for full, dark tone
Professional euphonium
Cup Depth
The Kelly 51D-EU has a — cup while the Bach 17D has a shallow 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.