Bach 15E vs Yamaha SL-46BS
The Yamaha SL-46BS has a wider cup diameter.
The internal diameter of the cup, measured at the widest point inside the rim.
Mouthpiece A
Bach 15E
• Trombone
Cup diameter24.40 mm / 0.9606 in
Best suited for
High-volume projection — open throat for power
vs
Mouthpiece B
Yamaha SL-46BS
• Trombone
Cup diameter24.58 mm / 0.9677 in
Best suited for
High-volume projection — open throat for power
Cup Diameter
The Yamaha SL-46BS has a cup diameter of 24.58 mm / 0.9677 in compared to 24.40 mm / 0.9606 in on the Bach 15E — a difference of 0.18 mm / 0.0071 in. A wider cup generally produces a fuller, darker tone but requires more air support.
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.