I am having trouble in playing low b note on alto sax. I can play low b flat, c and c # with out any problem. My sax is OK. When I play low b, I get the fuzzy sound or note doesn't come at all.
Low b flat is coming OK. I see one pad opening when going from low b flat to b. So I doubt about leak. If there is leak then I should have problem with b flat, but I don't have
Not necessarily - you can play some notes in the lower register quite normally even with your octave key open - some notes you will find easier than others some will be difficult to achieve ( by having the octave key open you are effectively creating a leak. So having one note play below the note you are having difficulty with does not mean you don't have a leak above it.
It is to do with harmonics, fundamentals and acoustics.
Leak aside and without having the instrument, it is difficult to ascertain what's causing this, however there are a few options.
The link between your low B to low C# could be out of regulation. - There is a mechanism that keeps the low C# from opening when the low B spatula Key is pressed and the low C# key is inadvertently touched creating a leak.
You could for example when playing low B, be touching the low C# spatula (key button).
The Low Bb key may not be venting (opening)properly/fully. This could be caused by the spring coming loose in the post, or coming of off its latch , or lost its tension on your low Bb key, thus making it not open fully. It could also be that the Low Bb bumper is not regulated properly - thus restricting the key from opening fully.
The mechanism that keep your G# key closed when playing the bell keys could be leaking enough to affect the B but not the low C# and Bb. - Try playing a low D and then keep playing the D and press the G# paddle to see if there is a difference in tone and or resistance.
You could try playing each note on the sax and get someone else to press each key pad to see if you can find a leak.
Your best bet is to take it to a reputable tech, ask them to show you what the problem is (if any) and give you a price on how to rectify it.
Good luck and let us know how you get on.
I told you...special acoustic thingsIt reduces the volume in that area of the saxophone which brings the harmonics more in tune with one another. A "warble" is created when there are harmonics stronger than the fundamental that are out of tune with one another and fight back and forth to control the mode locking or as Benade calls it "the regime of oscillation".