Bach 30E vs Yamaha BB-BOBO-SOLO-GP
The Yamaha BB-BOBO-SOLO-GP has a wider cup diameter, the Bach 30E has a larger throat opening.
Cup Diameter
The Yamaha BB-BOBO-SOLO-GP has a cup diameter of 32.20 mm / 1.2677 in compared to 30.00 mm / 1.1811 in on the Bach 30E — a difference of 2.20 mm / 0.0866 in. A wider cup generally produces a fuller, darker tone but requires more air support.
Cup Depth
Both mouthpieces share a shallow cup depth, so the sound character from depth alone will be very similar.
Throat Diameter
The Bach 30E has a wider throat (8.33 mm / 0.3280 in vs 7.50 mm / 0.2953 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.