Bach 12E vs Schilke 40B
The Bach 12E has a wider cup diameter, the Schilke 40B has a larger throat opening.
Cup Diameter
The Bach 12E has a cup diameter of 24.50 mm / 0.9646 in compared to 22.51 mm / 0.8862 in on the Schilke 40B — a difference of 1.99 mm / 0.0783 in. A wider cup generally produces a fuller, darker tone but requires more air support.
Cup Depth
Both mouthpieces share a shallow cup depth, so the sound character from depth alone will be very similar.
Throat Diameter
The Schilke 40B has a wider throat (5.95 mm / 0.2343 in vs 5.85 mm / 0.2303 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.