I don't see a PM option here so here goes. You said your speakers are 30 or 40 years old.
If they are electrolytic then by all means swap them all out. You might be able to find film to replace them with at a reasonable price. If not Nichicon has an audio line of caps that are all gold bodied. They are the best electrolytics available today.
If they are electrolytic then by all means swap them all out. You might be able to find film to replace them with at a reasonable price. If not Nichicon has an audio line of caps that are all gold bodied. They are the best electrolytics available today.