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

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

Mouthpiece A

Bach 15D

• Baritone / Euphonium

Backbore—

Best suited for

📣High-volume projection — open throat for power

Mouthpiece B

Bach 18

• Baritone / Euphonium

Backbore—

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.