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"Giant" sousaphones aren't so much big bell size as big bore.

I saw a 32 inch bell sousaphone a few years back. It wasn't a jumbo it just had a huge bell, and looked out of porportion. Dont remember the maker

The large diameter sousaphone bells I've seen are for "show" and not projection. At one time, the consenus among Martin Mammoth sousaphone owners seemed to be that a small diameter bell, about 24-inches, projected best...though Martin sousa bells were available to at least 30-inches.

The problem is that the _length_ of the bell flare past the elbow does not appreciably increase with the larger diameters, so the flare becomes less like a _cone_ and more like a _pancake_. You can appreciate that something conical will project sound better than something flat.

One of Dr. Young's archived posts refers to the angle (about 40 degrees) off the bell's axis at which the flare no longer contributes to the instrument's sound:
http://www.chisham.com/tips/bbs/sep2001 ... 69929.html

If you're primarily interested in a sousaphone that _plays well_, you might better consider a smaller diameter.....but more conical.....bell. A disproportionately large bell on a sousaphone can look rather ridiculous when viewed in profile, IMHO.

More reasons I prefer the 24 inch bell, in addition to being easier to navigate.