WOW!!! i am overwhelemed by the response. thx soooo much guys they are ALL good advice! i'll try a few long notes and check if the throat open/close is causing it and will get back to you tomorrow guys. once again thx v.much, much apreciated!! oh by the way i have regularly trained(and still do) my facial muscles especialy the ones needed for embucher for the last 2 years: upto strength 4 vandoren and long notes, jet out water and control the trajectory of the waterflow and rate etc -also my fingers are solid as i do play other instruments and occastional forearm curls

golferguy, wht i meant about my emboucher is that it IS constant in its configuration regardless of wht note i play, jaw is always dropped to let the reed vibrate freely, i.e i am NOT altering emboucher for different notes

sorry about the 3 seperate posts. i have a feeling golferguy675 may have identified my problem, fingers crossed, cannot wait until i try it out tomorrow AM. also leak test was ok no leaks detectd, pads are OK. its the throat that have not covered yet. it did cross my mind that it has to do with the air stream so was adjusting the tounges position alone but not throat as i thought the throat would always be open :(

One more suggestion because I have had this precise problem. Go ahead and close all of the keys to low D and then I would like for you to with all the keys closed see if the G# key moves at all so you are going to have to use your pinky on the left hand while all other keys are closed and try and tril the G# key...you don't have to play any notes...in fact you should be looking at the key. If that G# key moves at all, then you only need to get a small screwdriver and tighten the screw that holds that key down. I suspect that what you have is a small and I mean small leak but it is enough to make the lower register extremely frustrating. You shouldn't have to drop your jaw at all to hit the low end and could even get subtones if every key is sealing properly. Give it a try.