Conn Director Trumpet - Coprion Bell - preowned Ser#P-79552
What is Coprion?
The process necessary for producing the Coprion bell was developed by Conn in 1938. It consists of electrolytically depositing COPper IONns (hence the name Coprion) onto a stainless steel precision form accurate to millionths of an inch (so Conn said in its 1959 catalog), creating a seamless bell. Coprion isn't the same as a "rose brass" or "red brass" bell; these are brass bells with a higher copper content. Coprion is 100% pure copper.
In its advertising for the Coprion bell, Conn showed diagrams of the structure of "ordinary" brass bells compared to the Coprion bell. The brass bell showed an "irregular and hodge podge" crystal structure with comparatively large crystals, while the Coprion bell showed "ions of pure copper side by side in regular, close knit conformation and at right angles to the surface of the metal".
What does Coprion do to the sound and the way the instrument plays?
It is said that on an instrument with a Coprion bell "you can't overblow or 'crack' a note." Also, according to Conn, "Coprion has a special characteristic which permits great dynamic range without change in tone color."
It is generally accepted that high(er) copper content bells make the sound "darker" and have better projection.
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