Hello all. I'm new here, and new to owning vintage JBL's. After purchasing a beat up pair for fairly cheap, I noticed that the mid-range, and tweeter didn't work. I poked around online and read how someone recommended turning the "brilliance" and "presence" adjustment knobs. I tried that and it does work, but it has to be in just right the spot to get all the speakers to work, with the mid range being the most picky.

I'm assuming those adjustments weren't for turning the mid-ranges and tweeters off an on, right? How can I fix this? Can the crossovers be re-capped to fix this??

Thanks!