Bach 18 vs Schilke 69C4
The Schilke 69C4 has a wider cup diameter, the Schilke 69C4 features a deeper cup, the Bach 18 has a larger throat opening.
Cup Diameter
The Schilke 69C4 has a cup diameter of 32.76 mm / 1.2898 in compared to 32.10 mm / 1.2638 in on the Bach 18 — a difference of 0.66 mm / 0.0260 in. A wider cup generally produces a fuller, darker tone but requires more air support.
Cup Depth
The Schilke 69C4 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
The Bach 18 has a wider throat (9.00 mm / 0.3543 in vs 8.33 mm / 0.3280 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.