Bach 12E vs Marcinkiewicz ET3C. Loper
The Marcinkiewicz ET3C. Loper has a wider cup diameter, the Marcinkiewicz ET3C. Loper features a deeper cup, the Marcinkiewicz ET3C. Loper has a larger throat opening.
Cup Diameter
The Marcinkiewicz ET3C. Loper has a cup diameter of 25.10 mm / 0.9882 in compared to 24.50 mm / 0.9646 in on the Bach 12E — a difference of 0.60 mm / 0.0236 in. A wider cup generally produces a fuller, darker tone but requires more air support.
Cup Depth
The Marcinkiewicz ET3C. Loper has a deep cup while the Bach 12E has a shallow cup. Deeper cups favor a darker, richer sound; shallower cups provide more brightness and easier upper register.
Throat Diameter
The Marcinkiewicz ET3C. Loper has a wider throat (5.94 mm / 0.2339 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.