JBL L-300 Summit Are they still any good?

Thanks for the information. Do you know how I can find the new replacement diaphragms ?

Great, I love the older JBL's. I have a couple pair myself. Glad you know what you are doing. For me, Clarity or Mundorf caps, a source  Capacitors: Madisound Speaker Components (madisoundspeakerstore.com). Not sure how their prices compare. New diaphragms can be found on ebay if you are persistent. I would NOT change diaphragms unless they are really needed. Originals are the best unless they are auditorily defective. Watch out for made in China copies, they are not good.

If the 077 prism tweeters have the blue ring diaphragms, they sound better than the newer gold ring diaphragms and you simply cannot find the blue ring diaphragms as replacements. I've been watching for 10+ years and only saw one on ebay and missed it. I have one in case of a failure!

Thanks for your information pulled the other speaker apart today. Just fired them up! For old cap’s they still sound good. I have done a lot of business with Madisound with all my L-100 restorations. I still have a ton of the LE 5-2, mid
LE 25-1 tweets and 8 123A-1 and -3 woofers. I need to start unloading the extra parts. I watched a interview with Nelson Pass he said he may have improved the L 300 crossovers a bit but still felt  JBL did an excellent job on the configuration.

Yes JBL was one of the top back then, older ones, 60/70. I'm sure the caps are still good enough. As you know, they have made some improvements in capacitors since these were made. Could have already been upgraded I suppose.