I just got a pair of the Energy RC10's today. On the rear of each grill are 6 silver magnetic stubs. On one grill 2 of the stubbs were covered with black rubber. The other 4 were not. On the second grill none of the 6 silver stubs have the black rubber coating. Were all the stubs supposed to have this rubber covering so they don't scratch the speaker when they are attached? I'm confused as to why only 2 out of a total of 12 stubbs would be covered in black rubber but the rest aren't.