Which has a bigger cup — Bach 17D or Kelly 51D-EU?

The Kelly 51D-EU has a cup diameter of 25.40 mm / 1.0000 in compared to 24.20 mm / 0.9528 in on the Bach 17D — a difference of 1.20 mm / 0.0472 in. A wider cup generally produces a fuller, darker tone but requires more air support.

How does cup depth compare between Bach 17D and Kelly 51D-EU?

The Kelly 51D-EU has a — cup while the Bach 17D has a shallow cup. Deeper cups favor a darker, richer sound; shallower cups provide more brightness and easier upper register.

Bach 17D vs Kelly 51D-EU

Name: Kelly 51D-EU
Brand: Kelly

The Kelly 51D-EU has a wider cup diameter, the Kelly 51D-EU features a deeper cup.

Overall Comparison Cup Diameter Cup Depth Rim Width Throat Diameter Backbore Finish Material

The taper behind the throat leading to the shank. Affects projection and tone character.

Mouthpiece A

Bach 17D

• Baritone / Euphonium

Backbore—

Best suited for

📣High-volume projection — open throat for power

Mouthpiece B

Kelly 51D-EU

• Baritone / Euphonium

Professional

BackboreL

Best suited for

🎻Orchestral playing — large cup for full, dark tone

📋Professional euphonium

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.

Open in interactive tool + Add third mouthpiece Bach 17D details Kelly 51D-EU details Bach 17D equivalents Kelly 51D-EU equivalents

Bach 17D vs Kelly 51D-EU

Playing Characteristics

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Which is better?

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