Bach 10½A vs Bach 9
The Bach 9 has a wider cup diameter.
Mouthpiece A
Bach 10½A
• Cornet
Cup diameter15.90 mm
Cup depthVery deep
Rim width—
Throat diameter3.66 mm
Backbore—
Finish—
Material—
vs
Mouthpiece B
Bach 9
• Cornet
Cup diameter16.05 mm
Cup depthVery deep
Rim width—
Throat diameter3.66 mm
Backbore—
Finish—
Material—
Cup Diameter
The Bach 9 has a cup diameter of 16.05 mm compared to 15.90 mm on the Bach 10½A — a difference of +0.15 mm. A wider cup generally produces a fuller, darker tone but requires more air support.
Cup Depth
Both mouthpieces share a very deep cup depth, so the sound character from depth alone will be very similar.
Throat Diameter
Throat diameters are essentially identical at 3.66 mm, so resistance feel will be comparable.
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.