The original tweeter in all of these are the Klipsh K77, a Klipsch branded EV T-35. They are excellent tweeters. Originally, the diaphragms came with very fine wires attached, kind of like a human hair. They frequency burned out. But replacement diaphragms are available with beryllium/copper leads that will not burn out.
Replacing the diaphragm will be tricky for the novice, but is doable. Or one of the speaker repair houses can do it.
A big step up from the EV T-35 is the EV T-350. They are spendy on the used market and may require a bigger hole to be cut in the cabinet.
Bob Crites makes a replacement tweeter that a drop in and is based on a currently available horn tweeter. They are not to my taste but YMMV.