Schilke 66 vs Yamaha BB-64
The Schilke 66 has a wider cup diameter, the Yamaha BB-64 has a larger throat opening.
Cup Diameter
The Schilke 66 has a cup diameter of 31.52 mm / 1.2409 in compared to 30.45 mm / 1.1988 in on the Yamaha BB-64 — a difference of 1.07 mm / 0.0421 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
The Yamaha BB-64 has a wider throat (8.35 mm / 0.3287 in vs 8.33 mm / 0.3280 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.