sax pads - soft vs hard

I think the demonstration of Jim slapping his hand or a hard pad against the metal tube, is like the test of popping the keys - it's turning the body tube into a sort of tuned percussion instrument. The sound tells something about the seal - if the sax has leaks, you won't get that bottom-of-the-well resonant sound. But although the percussive effect of the pad or hand surface depends on the softness of the pad, it is not the same as what happens inside a saxophone when you're blowing it.