Which has a bigger cup — Kelly 12C or Yamaha SL-48S-GP?

The Yamaha SL-48S-GP has a cup diameter of 25.25 mm / 0.9941 in compared to 24.13 mm / 0.9500 in on the Kelly 12C — a difference of 1.12 mm / 0.0441 in. A wider cup generally produces a fuller, darker tone but requires more air support.

How does cup depth compare between Kelly 12C and Yamaha SL-48S-GP?

The Yamaha SL-48S-GP has a medium cup while the Kelly 12C has a shallow cup. Deeper cups favor a darker, richer sound; shallower cups provide more brightness and easier upper register.

Kelly 12C vs Yamaha SL-48S-GP

Name: Yamaha SL-48S-GP
Brand: Yamaha

The Yamaha SL-48S-GP has a wider cup diameter, the Yamaha SL-48S-GP features a deeper cup.

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

Base metal or construction (e.g. brass, stainless steel, plastic). Influences weight, response, and tone color.

Mouthpiece A

Kelly 12C

• Trombone

Lead

MaterialLexan polycarbonate

Best suited for

📋Lead trombone; smallest cup

Mouthpiece B

Yamaha SL-48S-GP

• Trombone

Material—

Best suited for

📣High-volume projection — open throat for power

Material

The Kelly 12C is described as Lexan polycarbonate, and the Yamaha SL-48S-GP as unspecified. Material affects mass, warmth, and how quickly the piece responds.

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.

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Kelly 12C vs Yamaha SL-48S-GP

Material

Playing Characteristics

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