Do Banana Plug Adaptors Degrade SQ?

Update to what I posted earlier.
I found the service data for the JBL L65 speaker. 

L65s do use a different speaker binding post arrangement then the 43xx/44xx series.  Original L65 binding posts are JBL part number 56130 (black), 56131 (red).

I can't tell for sure, but it looks as though the original binding posts are shorter and smaller diameter.  The threaded post looks hollow.  If that is the what you find, measure the internal diameter of the threaded post.

If you find it to be around 1/8" or 3mm, then you can use a "miniature" banana plug like the 2944.

https://www.pomonaelectronics.com/products/hardware/miniature-banana-plug-solderless

I use bananas from KLE Innovations - they are the very best I have found to date and make a noticeable improvements in dynamics, clarity details and image.

But they are a little more fragile than most others, so if you cables are heavy (larger than 10 gauge) and the binding posts are further than 20" off the ground th bananas may work loose

I also found these bananas to perform better than bare wire or silver plated copper spade connectors

regards

No.

Just like any other connector type, they are just another connector.  Unless they are grossly underrated for the job they are assigned to, or corroded to the point where they do not conduct properly, all conductors are about the same.

Yes, but it depends on the quality. The quality we have now is much better than what was available in the past but even so, this is worth a read:http://www.tempoelectric.com/Wire_and_Cable_Facts.pdf

For what it's worth, I prefer bananas for their ease of use and the solid and stable connection I get.

All the best,
Nonoise