Bach 6½A (small shank) vs Bach 9
The Bach 6½A (small shank) has a wider cup diameter.
Mouthpiece A
Bach 6½A (small shank)
• Baritone / Euphonium
Cup diameter25.40 mm
Cup depthDeep
Rim width—
Throat diameter5.85 mm
Backbore—
Finish—
Material—
Best suited for
Orchestral playing — large cup for full, dark tone
High-volume projection — open throat for power
vs
Mouthpiece B
Bach 9
• Baritone / Euphonium
Cup diameter24.72 mm
Cup depthDeep
Rim width—
Throat diameter5.85 mm
Backbore—
Finish—
Material—
Best suited for
Orchestral playing — large cup for full, dark tone
High-volume projection — open throat for power
Cup Diameter
The Bach 6½A (small shank) has a cup diameter of 25.40 mm compared to 24.72 mm on the Bach 9 — a difference of +0.68 mm. 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
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.