Which has a bigger cup — Bach 12E or Kelly 51D?

The Kelly 51D has a cup diameter of 25.40 mm / 1.0000 in compared to 24.50 mm / 0.9646 in on the Bach 12E — a difference of 0.90 mm / 0.0354 in. A wider cup generally produces a fuller, darker tone but requires more air support.

How does cup depth compare between Bach 12E and Kelly 51D?

The Kelly 51D has a — cup while the Bach 12E has a shallow cup. Deeper cups favor a darker, richer sound; shallower cups provide more brightness and easier upper register.

Bach 12E vs Kelly 51D

Name: Kelly 51D
Brand: Kelly

The Kelly 51D has a wider cup diameter, the Kelly 51D 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 12E

• Trombone

Material—

Best suited for

📣High-volume projection — open throat for power

Mouthpiece B

Kelly 51D

• Trombone

Professional

MaterialLexan polycarbonate

Best suited for

🎻Orchestral playing — large cup for full, dark tone

📋Professional euphonium and trombone players

Material

The Bach 12E is described as unspecified, and the Kelly 51D 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 12E details Kelly 51D details Bach 12E equivalents Kelly 51D equivalents

Bach 12E vs Kelly 51D

Material

Playing Characteristics

What Do These Model Names Mean?

What Changes If You Switch?

Which is better?

Compare Bach 12E with others

Compare Kelly 51D with others

Popular Trombone comparisons

Bach vs Kelly

Browse by specification