Yamaha HR-31B vs Yamaha HR-34B
The Yamaha HR-34B has a wider cup diameter.
The internal diameter of the cup, measured at the widest point inside the rim.
Mouthpiece A
Yamaha HR-31B
• French Horn
Cup diameter17.47 mm / 0.6878 in
Best suited for
High-volume projection — open throat for power
vs
Mouthpiece B
Yamaha HR-34B
• French Horn
Cup diameter18.07 mm / 0.7114 in
Best suited for
High-volume projection — open throat for power
Cup Diameter
The Yamaha HR-34B has a cup diameter of 18.07 mm / 0.7114 in compared to 17.47 mm / 0.6878 in on the Yamaha HR-31B — a difference of 0.60 mm / 0.0236 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.