Bach 18D vs Schilke 51D
The Schilke 51D has a wider cup diameter, the Schilke 51D features a deeper cup, the Schilke 51D has a larger throat opening.
Cup Diameter
The Schilke 51D has a cup diameter of 25.55 mm compared to 24.20 mm on the Bach 18D — a difference of +1.35 mm. A wider cup generally produces a fuller, darker tone but requires more air support.
Cup Depth
The Schilke 51D has a medium cup while the Bach 18D has a shallow cup. Deeper cups favor a darker, richer sound; shallower cups provide more brightness and easier upper register.
Throat Diameter
The Schilke 51D has a wider throat (7.04 mm vs 5.85 mm). 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.