EB in NYC

I have the Quintet speakers and the four satellite speakers are so sitting so loose on the base that I have to prop them up. I've looked in the owner's manual and it seems that I must not be the only one with this problem since it "sort of" describes a fix, adjusting the nut at the top of the bracket. I've tried this several times and the thing does not budge a millimeter. Has anyone had this problem? Any recommended fix? Thanks for your help...

Hey sorry if this is a dumb question, I live in an apartment building and my SW is sitting on the floor....I am worried that the intense stuff is going to shake the plaster off my downstairs neighbor's ceiling. Is there any recommended way to prevent that rumbling and low-end vibration from going through the floor??? Thanks....