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hrender wrote:Not sure how those widely-flared bells affect intonation.

Nothing to worry about, I guess - anyway I haven't heard that sousaphones are notably worse for intonation.

My guess is that the big Ebs of the early 20th century invariably came with wide bell flares because a bass tuba played in the contrabass range benefits from a more full, less punchy sound. (Which I understand to be the main effect of a wide bell flare.)