Bach 1½C vs Schilke 20D2d
The Schilke 20D2d has a wider cup diameter, the Schilke 20D2d features a deeper cup, the Bach 1½C has a larger throat opening.
Cup Diameter
The Schilke 20D2d has a cup diameter of 17.73 mm / 0.6980 in compared to 17.00 mm / 0.6693 in on the Bach 1½C — a difference of 0.73 mm / 0.0287 in. A wider cup generally produces a fuller, darker tone but requires more air support.
Cup Depth
The Schilke 20D2d has a deep cup while the Bach 1½C has a medium cup. Deeper cups favor a darker, richer sound; shallower cups provide more brightness and easier upper register.
Throat Diameter
The Bach 1½C has a wider throat (3.66 mm / 0.1441 in vs 3.65 mm / 0.1437 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.