Wobble vs Vibrato

I am not a voice teacher...the "wooble" represents a deterioration in the voice and it is always accompanied by dimished vocal abilities while it affects different areas of the voice. Two perfect examples of different area wobbles are of course Callas' in her high notes, that was gradually followed by the loss of her high notes and Sutherland's extremely bizarre wobble that did not occur in her high notes that remained spectacular almost till the end of her career, but in the middle of her voice (perfect example her studio Esclarmonde with high notes of absolute perfection and a middle-voice "Regardeux les..." that wobbles so, that it actually creates the feeling of a very old voice). Sutherland's middle-voice-wobble was accompanied by a loss of her vocal freshness and of the "gliding-through-the-notes" effect that so characterised her miraculous singing in the 60s and early 70s. I never understood what region of the voice is being attacked first by the "wobble". Is it the region mostly forced by the singer? the one mostly over-used? the one less talented? the one with the worse support or placement? There are of course singers with natural "wobbly-vibrati" that were there even when the singers were at their absolute vocal peak and didn't affect their ability to sing high notes. Perfect examples: G Jones and Lucia Popp. Some of them had the vibrato at first and then managed to control it and then it re-appeared in their old age (Callas, L Price). Callas herself when the first signs of wobble appeared in 1955, she had said: "They say my high notes are not stable, they should ask my mother that forced me to sing Santuzza when I was 14!"I think that two singers have proven their ability to overcome the threat of wobble despite their old ages: Edita Gruberova and Christa Ludwig. I have come to sincerely believe that Edita on this matter has made a deal with Lucifer :))Theo