Without knowing what speaker it is, I would suggest removing the grilles (if any) before going further. Some grille frames are steel or aluminum and may very well cause an audible rattle if not secured against the speaker or if the frame came loose at a joint.
Help needed with Rattle in my floorstanding speakers.
Help and suggestions needed with a rattling noise in my speakers.
I was playing a song called fading sun by Terje Isungset and it has the deepest bass note I have ever heard and one of my floorstanding speakers had a very noticeable rattle that I can hear coming from the upper part of the cabinet with the lowest bass note of the track. Not sure why but what is your recommendation to locate and hopefully fix this rattle. Thank you!