[FStephenMasek]

So, they're early "drone cones", sans voice & fieldcoils? My Altec 890C Bolero speakers each have a 10" speaker and a 10" "passive radiator".

Mike

They are different than those passive radiators in your speaker, as they are specifically intended to deal with vibrations from the wood cabinet. Here are two articles on them:

http://www.tuberadioland.com/philco38-116XX_main.html

scroll down on this site:
http://www.philcorepairbench.com/tips/svctip38.htm