Bruno Tilz 211-D 7 vs Kelly 31
The Bruno Tilz 211-D 7 has a wider cup diameter, the Kelly 31 features a deeper cup, the Bruno Tilz 211-D 7 has a larger throat opening.
Cup Diameter
The Bruno Tilz 211-D 7 has a cup diameter of 19.00 mm / 0.7480 in compared to 17.53 mm / 0.6902 in on the Kelly 31 — a difference of 1.47 mm / 0.0579 in. A wider cup generally produces a fuller, darker tone but requires more air support.
Cup Depth
The Kelly 31 has a — cup while the Bruno Tilz 211-D 7 has a shallow cup. Deeper cups favor a darker, richer sound; shallower cups provide more brightness and easier upper register.
Throat Diameter
The Bruno Tilz 211-D 7 has a wider throat (4.30 mm / 0.1693 in vs 3.80 mm / 0.1496 in). A wider throat allows more air through, increasing volume and projection but reducing resistance.
Material
The Bruno Tilz 211-D 7 is described as unspecified, and the Kelly 31 as Lexan polycarbonate. Material affects mass, warmth, and how quickly the piece responds.
Which is better?
The Bruno Tilz 211-D 7 is designed for catalog playing, while the Kelly 31 targets general use. Your best choice depends on your musical context.