Bach 6 vs Yamaha SL-48DL
The Bach 6 has a wider cup diameter, the Yamaha SL-48DL features a deeper cup, the Yamaha SL-48DL has a larger throat opening.
Cup Diameter
The Bach 6 has a cup diameter of 25.50 mm / 1.0039 in compared to 25.25 mm / 0.9941 in on the Yamaha SL-48DL — a difference of 0.25 mm / 0.0098 in. A wider cup generally produces a fuller, darker tone but requires more air support.
Cup Depth
The Yamaha SL-48DL has a deep cup while the Bach 6 has a medium cup. Deeper cups favor a darker, richer sound; shallower cups provide more brightness and easier upper register.
Throat Diameter
The Yamaha SL-48DL has a wider throat (6.62 mm / 0.2606 in vs 5.85 mm / 0.2303 in). A wider throat allows more air through, increasing volume and projection but reducing resistance.
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.