Kelly 24AW vs Kelly JACOBS-SS
The Kelly JACOBS-SS has a wider cup diameter, the Kelly 24AW features a deeper cup.
Cup Diameter
The Kelly JACOBS-SS has a cup diameter of 31.75 mm / 1.2500 in compared to 31.24 mm / 1.2299 in on the Kelly 24AW — a difference of 0.51 mm / 0.0201 in. A wider cup generally produces a fuller, darker tone but requires more air support.
Cup Depth
The Kelly 24AW has a very deep cup while the Kelly JACOBS-SS has a medium cup. Deeper cups favor a darker, richer sound; shallower cups provide more brightness and easier upper register.
Material
The Kelly 24AW is described as Lexan polycarbonate, and the Kelly JACOBS-SS as 316 Surgical Stainless Steel. Material affects mass, warmth, and how quickly the piece responds.
Which is better?
The Kelly 24AW is designed for general playing, while the Kelly JACOBS-SS targets orchestral use. Your best choice depends on your musical context.