Bach 12 vs Bach 25
The Bach 12 has a wider cup diameter.
Mouthpiece A
Bach 12
• Tuba
Cup diameter32.75 mm / 1.2894 in
Cup depthMedium
Rim width—
Throat diameter8.33 mm / 0.3280 in
Backbore—
Finish—
Material—
Best suited for
High-volume projection — open throat for power
vs
Mouthpiece B
Bach 25
• Tuba
Cup diameter30.60 mm / 1.2047 in
Cup depthMedium
Rim width—
Throat diameter8.33 mm / 0.3280 in
Backbore—
Finish—
Material—
Best suited for
High-volume projection — open throat for power
Cup Diameter
The Bach 12 has a cup diameter of 32.75 mm / 1.2894 in compared to 30.60 mm / 1.2047 in on the Bach 25 — a difference of 2.15 mm / 0.0846 in. A wider cup generally produces a fuller, darker tone but requires more air support.
Cup Depth
Both mouthpieces share a medium cup depth, so the sound character from depth alone will be very similar.
Throat Diameter
Throat diameters are essentially identical at 8.33 mm / 0.3280 in, 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.