Which has a bigger cup — Bach 12C or Kelly BASS-BONE-LS?

The Kelly BASS-BONE-LS has a cup diameter of 27.69 mm / 1.0902 in compared to 24.50 mm / 0.9646 in on the Bach 12C — a difference of 3.19 mm / 0.1256 in. A wider cup generally produces a fuller, darker tone but requires more air support.

How does cup depth compare between Bach 12C and Kelly BASS-BONE-LS?

The Kelly BASS-BONE-LS has a — cup while the Bach 12C has a shallow cup. Deeper cups favor a darker, richer sound; shallower cups provide more brightness and easier upper register.

Bach 12C vs Kelly BASS-BONE-LS

Name: Kelly BASS-BONE-LS
Brand: Kelly

The Kelly BASS-BONE-LS has a wider cup diameter, the Kelly BASS-BONE-LS 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

Bach 12C

• Trombone

Material—

Best suited for

📣High-volume projection — open throat for power

Mouthpiece B

Kelly BASS-BONE-LS

• Trombone

Bass

MaterialLexan polycarbonate

Best suited for

🎻Orchestral playing — large cup for full, dark tone

📋Bass trombone; tuba/euphonium doublers

Material

The Bach 12C is described as unspecified, and the Kelly BASS-BONE-LS as Lexan polycarbonate. 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.

Open in interactive tool + Add third mouthpiece Bach 12C details Kelly BASS-BONE-LS details Bach 12C equivalents Kelly BASS-BONE-LS equivalents

Bach 12C vs Kelly BASS-BONE-LS

Material

Playing Characteristics

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What Changes If You Switch?

Which is better?

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