Do pure copper banana plugs make a difference in the quality of the speaker sound.

I've used a couple of different connectors

For spade connectors I use Furez silver plated copper - they have proven t be the best sounding spade connectors I have tried

For Bananas, Furez also produces a nice Silver Plated Banana
- BUT the Bananas plug I now use is from KLE Innovations - it is exceptional and are great for installing jumpers on Bi-wireable speakers

I found that silver plated copper provides the best details and clarity and if the silver plate does tarnish then reseating the plug will effectively clean the tarnish at the point of contact (if there is any)

The black "Tarnish" on silver is the silver reating with the Sulpher in the air to produce silver sulphide, which actually conducts electricity, unlike the tarnish on bare copper, which MUST be cleaned/removed.

I did use the more affordable gold plated brass and Berylliam Copper type of banana for a while, but the silver plated copper are better - to these ears anyway

I use silver plated copper Mains connectors on my mains cables

And the RCA's from KLE Innovations are the best RCA's I have tried to date

Hope that helps - Steve

Banana plugs are great for experimenters and folks who make a lot of changes, but they don’t offer much contact area with the barrel they fit in to. You want maximum contact area.

For the most part - I agree with this statement

Some banana plugs have little spring clips on the pin
https://www.amazon.ca/Monoprice-109436-Plated-Speaker-Banana/dp/B0097JLQVC

Some banana plugs have a little bar on the pin
https://www.amazon.ca/GearIT-Premium-Braided-Speaker-Plated/dp/B0713ZDBM2/ref=redir_mobile_desktop?i...

Some Banana plugs rely on the spring effect of the pin itself to hold them in place - BUT they are generally NOT perfectly cylindrical, but elliptical.
https://www.amazon.ca/CERRXIAN-Speaker-Locking-Insulated-Connector/dp/B07TYK9SHQ/ref=sr_1_7?crid=3FV...

Some banana plugs have a screw lock that widens the pin
https://www.amazon.ca/Copper-Nakamichi-Speaker-Amplifier-Connector/dp/B072F1YRT7/ref=sr_1_17?crid=3F...

Many plugs are gold, rhodium or even platinum plated, but the issue here is - these metals requires a substrate to adhere to the base metal - that substrate normally has a much lower conductivity than the metals being used - so it impedes the transfer of the signal.

All of the above designs are flawed - they all fail to make use of the maximum possible contact area

However, the Banana plugs from KLE Innovations are precisely engineered and are perfectly cylindrical. They do Maximize the contract area of the entire pin - which in their case is approximately 1.1 sq cm. That’s possibly the biggest contact surface area of any speaker cable connectors - spades or bare wire!

https://kleinnovations.com/kle-innovations-klei-products/klei-harmony-connectors/klei-harmony-banana...

They are also NOT made of brass or some copper alloy - they are pure copper with a silver plating - so conductivity is maximized

BTW silver applied to copper does NOT requires any intermediate substrate plating material.

But they are not without any shortcomings
- they "may work loose" - IF the speaker cable is heavy - 10 gauge max
- they are a little fragile - they can bend out of shape IF you are not careful
- they can only be soldered onto the wire - some prefer crimp/screw style

Being silver plated they can "tarnish" and some people feel the need to clean them.

But here’s the thing, that dark discoloration is actually SILVER SULPHIDE
- Silver DOES NOT actually oxidize - it reacts with Sulphur in the air

And here’s the thing with Silver Sulphide...
- it does conduct electricity, but not quite as good as silver
- it is only ever microns thick
- restoring full performance is as easy as reseating the plug - i.e. "IF required" 

The KLEI Bananas are so well engineered/fabricated that air seldom gets into the joint, so the tarnishing effect on the pin is almost non existent.

If the plug gets deformed, restoring it’s shape is very easy.

They may not be for everyone - BUT if you want to improve the connection of your speaker cables - give them a try

They are the best Banana plug I have tried in the last 4 years

Here is my review...
http://image99.net/blog/files/tag-banana-plugs.html

Regards - Steve

@redwoodaudio - you are correct.

Fortunately - you can "adjust" the KLE Bananas quite easily.

I use an old banana plug similar to this one...
https://www.amazon.ca/GearIT-Premium-Braided-Speaker-Plated/dp/B0713ZDBM2/ref=redir_mobile_desktop?i...

I removed that little piece of wire on the pin. The shaft of this banana then fits nicely inside of the KLE Banana, making them expand ever so slightly to allow them to fit "Snuggly" in most binding posts.

But as I said, they are more delicate than many other alternatives, but they sound great

Regards - Steve

@cakids - I found some different information,,,

White gold was originally developed to imitate platinum (a naturally white metal). White gold is usually an alloy containing about 75% gold and about 25% nickel and zinc. If stamped 18 karat, it would be 75% pure gold.

and

Rhodium is a chemical element with the symbol Rh and atomic number 45. It is an ultra-rare, silvery-white, hard, corrosion-resistant, and chemically inert

But you are correct in that Rhodium is used a lot in jewelry, but in comparison to silver, coper and even gold - it is a poor conductor

From the table of Conductivity...

1. Silver’s conductivity is 106,
2. OCC copper is around 102
3. Copper is considered the reference at 100
4. Gold is 65
5. Rhodium is 38
6. Beryllium Copper is 22 (commonly used for plug contacts)
7. Platinum is 15

BTW - Conductivity is VERY important for contacts

Also - If the contacts of a plug are Gold or Rhodium plated, then a substrate plating is required, which normally has an even lower conductivity rating than the plating materials.

Regards