Bach 18 vs Yamaha HR-31D4
The Yamaha HR-31D4 has a wider cup diameter, the Yamaha HR-31D4 features a deeper cup.
Mouthpiece A
Bach 18
• French Horn
Cup diameter16.15 mm
Cup depthMedium
Rim width—
Throat diameter4.50 mm
Backbore—
Finish—
Material—
Best suited for
All-round versatile — balanced cup for general playing
High-volume projection — open throat for power
vs
Mouthpiece B
Yamaha HR-31D4
• French Horn
Cup diameter17.28 mm
Cup depthDeep
Rim width—
Throat diameter4.50 mm
BackboreSemi-narrow
Finish—
Material—
Best suited for
Orchestral playing — large cup for full, dark tone
High-volume projection — open throat for power
Cup Diameter
The Yamaha HR-31D4 has a cup diameter of 17.28 mm compared to 16.15 mm on the Bach 18 — a difference of +1.13 mm. A wider cup generally produces a fuller, darker tone but requires more air support.
Cup Depth
The Yamaha HR-31D4 has a deep cup while the Bach 18 has a medium cup. Deeper cups favor a darker, richer sound; shallower cups provide more brightness and easier upper register.
Throat Diameter
Throat diameters are essentially identical at 4.50 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.