Which has a bigger cup — Bach 15 or Bach 9?

The Bach 9 has a cup diameter of 24.72 mm / 0.9732 in compared to 24.40 mm / 0.9606 in on the Bach 15 — a difference of 0.32 mm / 0.0126 in. A wider cup generally produces a fuller, darker tone but requires more air support.

How does cup depth compare between Bach 15 and Bach 9?

Both mouthpieces share a deep cup depth, so the sound character from depth alone will be very similar.

Bach 15 vs Bach 9

Name: Bach 9
Brand: Bach

The Bach 9 has a wider cup diameter.

Overall Comparison Cup Diameter Cup Depth Rim Width Throat Diameter Backbore Finish Material

The taper behind the throat leading to the shank. Affects projection and tone character.

Mouthpiece A

Bach 15

• Baritone / Euphonium

Backbore—

Best suited for

🎻Orchestral playing — large cup for full, dark tone

📣High-volume projection — open throat for power

Mouthpiece B

Bach 9

• Baritone / Euphonium

Backbore—

Best suited for

🎻Orchestral playing — large cup for full, dark tone

📣High-volume projection — open throat for power

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.