Bach 4 vs Schilke 51D
The Bach 4 has a wider cup diameter, the Schilke 51D has a larger throat opening.
Mouthpiece A
Bach 4
• Baritone / Euphonium
Cup diameter26.00 mm / 1.0236 in
Cup depthMedium
Rim width—
Throat diameter5.85 mm / 0.2303 in
Backbore—
Finish—
Material—
Best suited for
High-volume projection — open throat for power
vs
Mouthpiece B
Schilke 51D
• Baritone / Euphonium
Cup diameter25.55 mm / 1.0059 in
Cup depthMedium
Rim width—
Throat diameter7.04 mm / 0.2772 in
BackboreJ .277"
Finish—
Material—
Best suited for
High-volume projection — open throat for power
Cup Diameter
The Bach 4 has a cup diameter of 26.00 mm / 1.0236 in compared to 25.55 mm / 1.0059 in on the Schilke 51D — a difference of 0.45 mm / 0.0177 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 Schilke 51D has a wider throat (7.04 mm / 0.2772 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.