Thanks Phil -- if you don't touch the cone it seems to want to "fall in place" and center pretty well by itself? usually the case?
I may just mark it where it sits and use the slow cure adhesive I have.
I guess I don't understand voice coils that well -- I was thinking that the field would be equal around the circumference and it would therefore center.
Guess not. Not a speaker "freak".
About 10 Amps DC could get it to center.
As suggested. you could use a low frequency tone (say 20Hz) and get the
speaker moving pretty good with your fingers holding the surround in
place. You won't hear any mechanical rubbing sound when you get it
right. The spider will help you with centering somewhat. Figure out a
way to clip the surround (maybe clothes pins) to hold it is place the
second time when you do it with glue.
You might want to make a ring the fits on the flat part of the surround
that glues to the frame. You can put this down and use the clothes pins
to clip that in place.
Of course once you have it centered you have the woofer straight you
turn off the tone and let the glue set.
When doing this you will change he woofer parameters somewhat. if the
surround is stiffer than the original the Vas will be lower and the Fs
may be higher. It may sound different that the opposite one when done
if your only repairing one of a pair.