The Bb is a very problematic tone on many clarinets. The hole has two functions. It should work as a tone hole when played as a B, and as a register hole when you play the upper register. These are two completely different things.
The 3 problems
1. As a tone hole, it should be placed in a different position and much larger.
2. As a register hole, it should have a different shape and help several notes to speak easily and precisely in pitch
3. The register sleeve also protrudes into the hole and causes problems for the air column. The created turbulence is difficult to control and creates resistance.
The 3 solutions
1. Practice a lot, compromise, and get used to all three problems, but that's not a very good solution. There are better ones.
2. We have developed a register tube that improves all three problems. The implementation of the solution is quick and easy. The L&P resonance tube will not be as good as the separate Bb resonance key, but still a significant and very economical improvement. Read more about it here: LP Registertube
3. The best solution by far is the Bb resonance mechanics. We offer various valve mechanisms to add a B resonance valve. They differ in design but not in functionality. The resonance flap opens automatically as soon as the A and register flaps are pressed together while the register pad closes.
This allows us to add a Bb resonance tone hole on one side that is perfectly placed and dimensioned to work as a pure tone hole and on the other side to optimize the size of the register hole for its purpose.