Bach 10½EW vs Bach 9D
The Bach 9D has a wider cup diameter.
The internal diameter of the cup, measured at the widest point inside the rim.
Mouthpiece A
Bach 10½EW
• Cornet
Cup diameter15.90 mm / 0.6260 in
Best suited for
Lead / commercial — shallow cup for brightness and range
vs
Mouthpiece B
Bach 9D
• Cornet
Cup diameter16.05 mm / 0.6319 in
Best suited for
Lead / commercial — shallow cup for brightness and range
Cup Diameter
The Bach 9D has a cup diameter of 16.05 mm / 0.6319 in compared to 15.90 mm / 0.6260 in on the Bach 10½EW — a difference of 0.15 mm / 0.0059 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.