Bach 12C vs Bach 17
The Bach 12C has a wider cup diameter, the Bach 17 features a deeper cup.
Mouthpiece A
Bach 12C
• Trumpet
Cup diameter15.20 mm / 0.5984 in
Cup depthMedium
Rim width—
Throat diameter3.66 mm / 0.1441 in
Backbore—
Finish—
Material—
vs
Mouthpiece B
Bach 17
• Trumpet
Cup diameter15.10 mm / 0.5945 in
Cup depthVery deep
Rim width—
Throat diameter3.66 mm / 0.1441 in
Backbore—
Finish—
Material—
Cup Diameter
The Bach 12C has a cup diameter of 15.20 mm / 0.5984 in compared to 15.10 mm / 0.5945 in on the Bach 17 — a difference of 0.10 mm / 0.0039 in. A wider cup generally produces a fuller, darker tone but requires more air support.
Cup Depth
The Bach 17 has a very deep cup while the Bach 12C has a medium cup. Deeper cups favor a darker, richer sound; shallower cups provide more brightness and easier upper register.
Throat Diameter
Throat diameters are essentially identical at 3.66 mm / 0.1441 in, so resistance feel will be comparable.
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.