Bach 18 vs Bach 7
The Bach 7 has a wider cup diameter.
Mouthpiece A
Bach 18
• Tuba
Cup diameter32.10 mm / 1.2638 in
Cup depthMedium
Rim width—
Throat diameter9.00 mm / 0.3543 in
Backbore—
Finish—
Material—
Best suited for
High-volume projection — open throat for power
vs
Mouthpiece B
Bach 7
• Tuba
Cup diameter33.25 mm / 1.3091 in
Cup depthMedium
Rim width—
Throat diameter9.00 mm / 0.3543 in
Backbore—
Finish—
Material—
Best suited for
High-volume projection — open throat for power
Cup Diameter
The Bach 7 has a cup diameter of 33.25 mm / 1.3091 in compared to 32.10 mm / 1.2638 in on the Bach 18 — a difference of 1.15 mm / 0.0453 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 9.00 mm / 0.3543 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.