Pics are hard to get due to the way they are installed. Here's an illustration, though.
http://thefirstgensite.com/library/68sm/acc/acc46.jpg

Put the top up. On the trunk side of the back seat support, locate four screw holes on each side. Place the special convertible rear speaker enclosures, which are shallow folded cardboard boxes that look like oversize, overthick fast food clamshell box halves, and screw the speakers in to the boxes into the braces using the male-female studs.

Now mark your convertible well to cut for the speaker grilles, pulling it down so the fabric lays nicely over the speakers, leaving just a little slack. Cut the openings in the well liner, install grilles to speakers and screw them into the studs.

Then put your top down, and you won't hear a thing. At least not anything decent.