Bells are the largest opening of the instrument and influence the sound, intonation and tonal stability in the high register. They are available in many different shapes, forms, materials, bores, thicknesses, and with or without keys. Since bores can change over time it can sometimes be advisable to rotate the bell to see if it sounds better in different positions.
The bells length and opening diameter have a big influence on intonation, especially on low E/long B. Choosing a shorter bell can help if these notes are too flat.
Bells can also facilitate intonation and venting with an extra low E resonance key. In many cases this solves the low E pitch problem and makes the sound of the low E fit much better into the scale. It will require that you have the low E mechanism installed to your instrument.
Most bells have a metal ring at the top as reinforcement against cracking during assembly. On new instruments, it is not uncommon to encounter problems fitting the bell all the way onto the lower joint. This is because the clarinets lower tenon can expand when humidified but the bells metal ring prevents the same level of expansion. If this occurs, follow the instructions already given for barrels.
The other ring found on most bells is the larger, lower ring. It often has a dull finish and is not silver-plated. Because the ring was shrunk and pressed onto the bell when it was made, any sliver plating would be damaged in the process.
Both upper and lower rings are very good protection against accidental damage.
Loose ring problems
When the humidity dips very low, rings often become loose and can buzz or rattle when playing. A quick and easy solution is to put a wet cloth around the ring or to ask your repairman to shrink the ring so that it fits again. If rings on the barrel or top of the bell become loose enough to be completely removed, a thin layer of paper can be placed around the wood and the ring pressed over it. Dont glue any of the rings.