Bach 12 vs Yamaha AH-38D4
The Bach 12 has a wider cup diameter, the Bach 12 has a larger throat opening.
Mouthpiece A
Bach 12
• Baritone / Euphonium
Cup diameter24.50 mm / 0.9646 in
Cup depthDeep
Rim width—
Throat diameter5.85 mm / 0.2303 in
Backbore—
Finish—
Material—
Best suited for
Orchestral playing — large cup for full, dark tone
High-volume projection — open throat for power
vs
Mouthpiece B
Yamaha AH-38D4
• Baritone / Euphonium
Cup diameter18.90 mm / 0.7441 in
Cup depthDeep
Rim width—
Throat diameter5.25 mm / 0.2067 in
BackboreStandard
Finish—
Material—
Best suited for
Orchestral playing — large cup for full, dark tone
High-volume projection — open throat for power
Cup Diameter
The Bach 12 has a cup diameter of 24.50 mm / 0.9646 in compared to 18.90 mm / 0.7441 in on the Yamaha AH-38D4 — a difference of 5.60 mm / 0.2205 in. A wider cup generally produces a fuller, darker tone but requires more air support.
Cup Depth
Both mouthpieces share a deep cup depth, so the sound character from depth alone will be very similar.
Throat Diameter
The Bach 12 has a wider throat (5.85 mm / 0.2303 in vs 5.25 mm / 0.2067 in). A wider throat allows more air through, increasing volume and projection but reducing resistance.
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.