Bach 18 vs Bach 4C
The Bach 4C has a wider cup diameter, the Bach 18 features a deeper cup.
Mouthpiece A
Bach 18
• Baritone / Euphonium
Cup diameter24.20 mm
Cup depthMedium
Rim width—
Throat diameter5.85 mm
Backbore—
Finish—
Material—
Best suited for
High-volume projection — open throat for power
vs
Mouthpiece B
Bach 4C
• Baritone / Euphonium
Cup diameter25.75 mm
Cup depthShallow
Rim width—
Throat diameter5.85 mm
Backbore—
Finish—
Material—
Best suited for
High-volume projection — open throat for power
Cup Diameter
The Bach 4C has a cup diameter of 25.75 mm compared to 24.20 mm on the Bach 18 — a difference of +1.55 mm. A wider cup generally produces a fuller, darker tone but requires more air support.
Cup Depth
The Bach 18 has a medium cup while the Bach 4C has a shallow 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 5.85 mm, 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.