Bach 15EW vs Bach 18C
The Bach 15EW has a wider cup diameter.
The internal diameter of the cup, measured at the widest point inside the rim.
Mouthpiece A
Bach 15EW
• Baritone / Euphonium
Cup diameter24.30 mm / 0.9567 in
Best suited for
High-volume projection — open throat for power
vs
Mouthpiece B
Bach 18C
• Baritone / Euphonium
Cup diameter24.20 mm / 0.9528 in
Best suited for
High-volume projection — open throat for power
Cup Diameter
The Bach 15EW has a cup diameter of 24.30 mm / 0.9567 in compared to 24.20 mm / 0.9528 in on the Bach 18C — a difference of 0.10 mm / 0.0039 in. A wider cup generally produces a fuller, darker tone but requires more air support.
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.