Bach 18 vs Yamaha HR-30B
The Yamaha HR-30B has a wider cup diameter, the Bach 18 features a deeper cup, the Bach 18 has a larger throat opening.
Cup Diameter
The Yamaha HR-30B has a cup diameter of 17.27 mm / 0.6799 in compared to 16.15 mm / 0.6358 in on the Bach 18 — a difference of 1.12 mm / 0.0441 in. A wider cup generally produces a fuller, darker tone but requires more air support.
Cup Depth
The Bach 18 has a medium cup while the Yamaha HR-30B has a shallow cup. Deeper cups favor a darker, richer sound; shallower cups provide more brightness and easier upper register.
Throat Diameter
The Bach 18 has a wider throat (4.50 mm / 0.1772 in vs 3.90 mm / 0.1535 in). A wider throat allows more air through, increasing volume and projection but reducing resistance.
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.