After several decades of California sunshine and (ahem) kickin' tha
phat jams from the killer pushbutton Blaupunkt AM radio, my '71
squareback's original under dash speaker was, well, toast.  I managed to
fish it out for a look-see, which was no easy task.  First thing to note:
do NOT remove the dash board cover  All the action takes place underneath
the dash.  Here's what I had to do:

1) Remove the radio.  Mine's bolted to the lip under the dash, right
in the center.

2) Remove the plastic fresh air hoses.  They slip off at each end.  Note
location and orientation of both of them before removal.

3) Remove ash tray.

4) Unscrew ash tray holder from front of dash, and remove holder.

5) Go fishing for the speaker.  It's held on by a big, giant clip!
You have to feel around and unhook one end of the clip, swing the clip
out of the way and then the speaker will fall right out.  Improvise.

6) I took the tattered speaker to my local Radio Shack and found one
of very similar dimensions.  Bought it.  (Maybe US$6-10, as I recall.)

7) Installation is the reverse of removal.  Well, almost.  The new
speaker was the slightest bit thicker and/or wider at just the wrong place,
making spring clip reinstallation quite difficult.  Not impossible, just
difficult.  Use gentle force.

Enjoy.  Your favorite chanteuse will no longer sound like she needs
a cough drop. :-)

(Note that these are the specific steps for a 1971 Type III.  There
are certainly going to be variations to the procedures for different
model years, but the general approach should be the same.)

-Greg
gregm@vwtype3.org