Compaq JBL Pro speakers - need to know polarity of power supply

My wife purchased these speakers at a garage sale and of course didn't
get the power supply. Radio Shack has a 12volt/1Amp replacement. I've
got the plug narrowed down to Radio Shack's "M", but need to know the
polarity of the speakers. It isn't stamped anywhere on them. I assume
it is - ---C •--- +. If anyone has these speakers can you confirm this
for me?
Thanks for your help.
Larry
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Larry Dawson

http://homepage.mac.com/capnlarry/

I don't know whether it's a virtue or a vice in me, but regularly
rereading favorite books has always been one of the quasi-
religious ceremonies with which I occupy my life.
Fritz Leiber