Pardon my ignorance when it comes to car audio, but what are these spacers that people keep talking about for when they install the 6.5" door speakers? Do they come in different sizes, and if so, what size do I need?

 

Spacers just 'lift' the speaker away from the door because the speaker depth is too much, may interfere with the window or outside door panel. For a 6.5" speaker you need a spacer that is basically a 6.5" ring for the speaker to sit against. I know people who have taken the grills that come with speakers & remove/cut off the mesh of the grill & use the remaining 'ring' as the spacer.

 

The best thing is to cut a piece of mdf to the shape you need.