[jaumes]

It´s possible raise the intonation in low D and C without using crescents. I´ve
raised low C, B and Bb, but this does not solve the problem.
Buescher Big B alto.
Thanks.

 

[MusicMedic]

It´s possible raise the intonation in low D and C without using crescents. I´ve
raised low C, B and Bb, but this does not solve the problem.
Buescher Big B alto.
Thanks.

These notes are usually not very flat on a Buescher Big B. Even with the stack keys very open, these notes are usually fairly in tune. I wonder if the problem is not something else, maybe mouthpiece.

To answer your question, it is only (practically) possible to raise the pitch of the low C and B tones with key heights. You can do this with a combination of raising the height of the low C and B pads and lowering the height of the rest of the pads.

 

[jaumes]

I´ve tested with diferents mouthpiece, meyers medium and large chamber, berg larsen rubber large chamber, beechler, morgan medium chamber, selmer C**, supersesion D, with negative results. Not tested with vintage mouthpieces, any suggestion?
Thanks for your answer Curt, I´ll test lowering all the key heights except C and B.