You need to only use banana plug connectors on your speaker cables. I have this problem on my Forte 4s. If you want to correct the looseness, remove the plate holding the binding posts and tighten the inner nut(s). When all nuts are tight, re-attach the plate to the speaker and use banana plugs.
Klipsch Cornwall iv loose binding post
What to do? How to fix?
Where I connect the positive red connection won’t tighten down…spinning not tightening as if there exists a loose connection, on the interior of the speaker. Do I need to invade the speaker? How?