- Surrey, UK
I don't know for sure but I strongly suspect it's because the bore is too big. Ideally the bore diameter should should be multiplied by the square root of 2, doubling the cross sectional area, to go down an octave. Using round figures a soprano clarinet has a bore of around 15mm which would imply a corresponding bass clarinet bore of around 21mm. Actual Boehm system clarinets have a bore of over 23mm. That's about 10% too big. They probably ended up like this to give them a bigger sound in the low register. When they were invented nobody expected expected them to play high notes much.
Some older German system basses have a bore size around 20mm which is out the other way. I've never played one but I strongly suspect that the clarion is a lot more stable on those instruments.
I have a metal bass clarinet made by Uebel that has a bore of about 19mm. It is quite a different beast to a normal, modern bass clarinet, including that the special mouthpiece fits over a corked neck, like a saxophone mouthpiece. The original Uebel mouthpiece isn't very good so I spoke to Ed Pillinger to see whether he could make me a one-off replacement. Here is what Ed told me about the bore.
Uebel bass clarinets had small German bores c. 19mms. I still have one of these, a low C bass that played wonderfully well, lovely tone and an agility enabling one to soar up to the upper reaches of the instrument with ease. Mine came with a small bore German bass clarinet mouthpiece designed traditionally for the reed to be held on with string. The only real drawback with this instrument was the lack of power when up against French big bore bass clarinets (usually c. 23mms). I tackled this problem by adapting a French style alto clarinet mouthpiece, enlarging the bore to the German bass mpc size and giving it a sort of C*-ish alto sax facing for alto sax reeds. I got a lot more power and overall dynamic range but the tone was rather poor compared to the German setup. I cured this to a great extent by making the chamber of the mouthpiece much smaller and again more like the internal volume of the German mpc. This made the sound much better, more focused and I arrived at a setup that could compete in a symphony orchestra. I made this mouthpiece for a number of players including Tony Pay.