Some time ago, I made a good deal on a pair of blown Fostex FD200 drivers. They are also 2″ drivers with little different specs. I will try them on the large Tractrix horns as well. Here are some pics on where I reconed them:
Maybe there is somebody out, who can solve this question: When I bought them, the blown diaphragms had already been removed. BUT there was this aluminum ring (see last two pictures). An identical ring was glued to the bottom of the new diaphragms. Now I am a little unsure on whether or not this ring has to be installed underneath the new diaphragms or if this ring was just not glued to the old diaphragms. Maybe the guy who removed the blown ones thought that these rings may belong to the driver.
The ring is necessary only when using older type diaphragms of this driver. In the older drivers, the diaphragm was centered by two pins, the newer ones have a groove (like mine). The ring adjust the position (heith) of the voice coil within the air gap. For the diaphragms shown, they are not required. Thanks go to Robert for solving this issue.