Bach 11C vs Bach 9
The Bach 9 has a wider cup diameter, the Bach 9 features a deeper cup.
The internal diameter of the cup, measured at the widest point inside the rim.
Mouthpiece A
Bach 11C
• Baritone / Euphonium
Cup diameter24.70 mm / 0.9724 in
Best suited for
High-volume projection — open throat for power
vs
Mouthpiece B
Bach 9
• Baritone / Euphonium
Cup diameter24.72 mm / 0.9732 in
Best suited for
Orchestral playing — large cup for full, dark tone
High-volume projection — open throat for power
Cup Diameter
The Bach 9 has a cup diameter of 24.72 mm / 0.9732 in compared to 24.70 mm / 0.9724 in on the Bach 11C — a difference of 0.02 mm / 0.0008 in. A wider cup generally produces a fuller, darker tone but requires more air support.
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.