Bach 17D vs Yamaha AH-37C4
The Bach 17D has a wider cup diameter, the Yamaha AH-37C4 features a deeper cup, the Bach 17D has a larger throat opening.
Cup Diameter
The Bach 17D has a cup diameter of 24.20 mm / 0.9528 in compared to 18.60 mm / 0.7323 in on the Yamaha AH-37C4 — a difference of 5.60 mm / 0.2205 in. A wider cup generally produces a fuller, darker tone but requires more air support.
Cup Depth
The Yamaha AH-37C4 has a medium cup while the Bach 17D has a shallow cup. Deeper cups favor a darker, richer sound; shallower cups provide more brightness and easier upper register.
Throat Diameter
The Bach 17D has a wider throat (5.85 mm / 0.2303 in vs 5.25 mm / 0.2067 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.