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Bach 15D vs Bach 18D

The Bach 15D has a wider cup diameter.

Overall Comparison Cup Diameter Cup Depth Rim Width Throat Diameter Backbore Finish Material
Mouthpiece A
    Bach 15D
    • Trombone
    Cup diameter24.40 mm / 0.9606 in
    Cup depthShallow
    Rim width—
    Throat diameter5.85 mm / 0.2303 in
    Backbore—
    Finish—
    Material—
    Best suited for
    📣High-volume projection — open throat for power
    vs
    Mouthpiece B
      Bach 18D
      • Trombone
      Cup diameter24.20 mm / 0.9528 in
      Cup depthShallow
      Rim width—
      Throat diameter5.85 mm / 0.2303 in
      Backbore—
      Finish—
      Material—
      Best suited for
      📣High-volume projection — open throat for power

      Cup Diameter

      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 18D — a difference of 0.20 mm / 0.0079 in. A wider cup generally produces a fuller, darker tone but requires more air support.

      Cup Depth

      Both mouthpieces share a shallow cup depth, so the sound character from depth alone will be very similar.

      Throat Diameter

      Throat diameters are essentially identical at 5.85 mm / 0.2303 in, so resistance feel will be comparable.

      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 15D details Bach 18D details Bach 15D equivalents Bach 18D equivalents

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