Testing speaker capacitors

The tweeter connection is covered with hard wax or plastic at the terminal box. How do I remove the hard stuff to disconnect the tweeter?

You really don't have to disconnect the tweeter to test it if you can get to it's terminals.

I want to switch L/R tweeters so I have to disconnect the bad one and connection is covered in hardened plastic.

It's probably hot glue.

You can use a hot knife, heat gun, or denatured alcohol to remove it.

Why go to the trouble to remove both tweeters just to check one? If you can't check the suspected bad one in it's cabinet, why not just remove it and touch the speaker wires to the terminals and play music through it at low volume?