The model number might be somewhere on a label (over the connections in the back). Hate to admit it, but I remember these from the mid-70's. They are a scaled-down version of their famous "heil" tweeters. The company still exists and they might be able to help. Here is their home page:
Now, whether it's worth it to repair them...I saw some reviews of their high end speakers at audio-review. Those were available for less than $500 used, like here:
Check out those tweeters! They are a very radical and famous design.
If that's the value of the high end speaker, I doubt that the cost to repair yours would be worth it. I checked ebay for parts. These tweeters might match:
Personally, I felt they were way over-priced when new, but there were people who loved them. If you ever manage to get them fixed, tell us how they sound to you.
By the way, those big ESS speakers at ebay are a real bargain, but they require alot of power to sound decent. Shipping..."They measure 36" inches high by 16"inches square and approx 50lbs each."...might be a bit high. These are the ones you can definitely get parts for.