Which has a bigger cup — Bach 15D or Bach 18?

The Bach 15D has a cup diameter of 24.40 mm / 0.9606 in compared to 24.20 mm / 0.9528 in on the Bach 18 — a difference of 0.20 mm / 0.0079 in. A wider cup generally produces a fuller, darker tone but requires more air support.

How does cup depth compare between Bach 15D and Bach 18?

The Bach 18 has a medium cup while the Bach 15D has a shallow cup. Deeper cups favor a darker, richer sound; shallower cups provide more brightness and easier upper register.

Bach 15D vs Bach 18

Name: Bach 18
Brand: Bach

The Bach 15D has a wider cup diameter, the Bach 18 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 15D

• Baritone / Euphonium

Material—

Best suited for

📣High-volume projection — open throat for power

Mouthpiece B

Bach 18

• Baritone / Euphonium

Material—

Best suited for

📣High-volume projection — open throat for power

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.