Sub Rattle

[max payne]

Hi i have just joined first of all i need to ask my sub keeps rattling the metal shelf,

i removed my orginal sub and installed a 12"jbl i couldnt fit it from above so i had to mount it from beneath the shelf, the trouble is that my metal shelf vibrates how do i get rid of it.And i also have an original working order pioner sub if anyone wants it.