Bach 4 vs Yamaha EP-51DS
The Bach 4 has a wider cup diameter, the Yamaha EP-51DS features a deeper cup, the Yamaha EP-51DS has a larger throat opening.
Cup Diameter
The Bach 4 has a cup diameter of 26.00 mm compared to 25.24 mm on the Yamaha EP-51DS — a difference of +0.76 mm. A wider cup generally produces a fuller, darker tone but requires more air support.
Cup Depth
The Yamaha EP-51DS has a deep cup while the Bach 4 has a medium cup. Deeper cups favor a darker, richer sound; shallower cups provide more brightness and easier upper register.
Throat Diameter
The Yamaha EP-51DS has a wider throat (7.11 mm vs 5.85 mm). 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.