The original Sousaphone was a large BBb tuba designed for use in Sousa's Band in the 1890s. The concept was simple: add a curve to the bell of a helicon so that the sound is directed upwards and not at the audience. The first Sousaphones, made by J.W. Pepper in about 1897 and shortly after by C.G. Conn were expressly made for use in Sousa's band. We do know that Sousa wanted the tubas to add the sound of the largest organ pipes to his band and had great appreciation for the very large European BBb tubas, including helicons, that were available. Shortly after the turn of the 20th Century, Conn developed a BBb Sousaphone (the term was originally considered a proper noun) that was even larger and more organ like in sound. They called this the Jumbo Sousaphone. The bore through the valves was .775" and the size of this tuba through its body was larger than any BBb instrument that had been made previously and in the hands of a very good player is indeed organ like. An instrument this size in standard tuba form would be difficult or impossible for all but the largest to hold in front of them while playing so the circular shape was especially important. Some time in the late 1910s, Conn started producing a recording, or forward facing 26" or 28" bell, in contradiction to Sousa's preference, but making them in the form of our modern marching band tuba, including all of them that I show here.
In the 1920s, King decided to do Conn one better by producing an even larger instrument with a bore measuring .815" and a bell rim diameter of 32". The body was actually very slightly smaller, being 1/4" smaller in diameter at the bell receiver (where the bell connects to the body). Conn made one special instrument to commemorate their 50th anniversary in business with a fully engraved 36" bell, but bells larger than 28" were only available by special order. Other US makers produced similarly large Sousaphones, including Buescher (Buescherphone) and Holton (Holtonphone). Martin (Mammoth) and York (Monster) made large Sousaphones with valve sections and bodies the same size as their largest upright tubas but with bell rims diameters of 28" or larger. King also produced a large Sousaphone with a 29" bell that they called the Giant. The first photo to the left shows my nephew Chris Menter holding the King Jumbo next to Dave Hayami with his Giant. For even more contrast, the second photo shows Chris next to Jim Self's Selfone being played by one of Jim's students. Next is a photos with another King Jumbo next to a Conn 20K with 28" bell (this is the largest Sousaphone that has been produced in the last 60 years) and a Conn Sousaphone with a 26" bell, which is the standard size bell on most instruments today. In this photo, on the extreme left, is the travel trunk case for the Jumbo. Fortunately, this has wheels on it, because it is large enough to hold both the Jumbo along with a standard size Sousaphone strapped in the lid.
The last two photos are of Conn Jumbo Sousaphones with front facing bells. This first is an example in its most common form, with satin silver plating and gold in the bell, being tested by the great Hollywood trombonist Alan Kaplan with the help of his friend, Ross DeRoche. Last is a gold plated example that was custom engraved for Earl Field, who played in Sousa's Band in the 1920s, although he wouldn't have been allowed to use this bell front version since Sousa only allowed the upright or "raincatcher" bell tubas in his band.