Conn 48K BBb Sousaphone Grand Jumbo
Date: 1920's, owned by Ian Church
This instrument is well named: "Grand Jumbo". Ian Church's research indicates that sousaphones could be ordered with custom bells from 26" to 34". This particular 48K has a 30" bell. It has a 0.772" bore (about #11¾). Compare that to the about 0.719" (#10) bore of the 36K Fiberglass model or the 0.734" (#10½) of the 20K. The 48K is the four valve version, the 46K is the three valve version. It was produced between at least 1924 and 1927.
What Conn said in 1926:
The New Wonder Model Sousaphone Grand Basses are the largest members of the Sousaphone family. Built in BBb, with either three of four valves, they add a deep and sonorous voice to any ensemble in which the may be used. The splendid impression made by these instruments in point of appearance is a matter of remark everywhere.
Due to the hydraulic expansion process of manufacture, these instruments are perfectly proportioned, and accurate intonation is therefore invariably obtained. The inside of the tubing is smooth as glass, having been "ironed out" by pressure of 10,000 pounds or more, and as a result the softest pianissimo passages, encountering little resistance, can be played with great effect. This is proof of the easy blowing quality of the Conn Sousaphone Grand Bass.
The adjustable bell has a two-fold advantage. It permits saving of space in packing, with corresponding decrease in liability to damage and also permits the tone of the instrument to be thrown in any desired direction.