Anyway.

Le lien que tu envoie dit pourtant l'inverse...

d'ailleurs sur le même site :
"The SM58 and SM57 do use the same cartridge. The grill, though, does effect the frequency response to some extent. At a distance, the difference is probably not noticable. But at extremely close distances, the difference is noticeable. Due to the grill, a person's mouth can get closer to the diaphragm of an SM57, thus causing more proximity effect and increased bass when compared to the SM58. "
La base du micro est la même : Unydine III
Après c'est Shure qui le dit :
"The SM58 and the SM57 share the same mic element, the Unidyne III. The only difference between the these two models is the grill design.
The grill design does affect the high frequency response, particularly above 8,000 Hz.
The SM57 grill design allows more proximity effect because the mic diaphragm can be placed closer to the sound source. Proximity effect increases each time the distance from the mic to the source is halved. When a mic is placed very close, it is quite easy to halve the distance: 1 inch to 1/2 inch; 1/2 inch to 1/4 inch; etc. Remove the ball grill from the SM58 and it will be more similar to the SM57 in its low frequency response.
Any other differences you hear between the SM57 and SM58 are likely to be subjective (psycho-acoustic) or due to slight manufacturing differences due to part tolerance. "