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

I tried many different connections, but by far the most natural and real sounding speaker cable connector is the ETI Research pure copper spade. I always solder and use Wondersolder with very good results.

These ETI bare copper spades are better sounding than Furutech gold plated FP-201, even when you solder them instead of clamping with the screws.

I don’t like “squeezing” a wire into a connection ( unless it is a thick solid core like AWG 16 or more). The thin wires will be squeezed and this is limiting the “electron flow” since the surface is damaged. 
And please DO NOT TIN ( solder) bare ends and put them into a screwed connection. This will not give a solid connection as the tinning makes the cable very soft and is flowing under the pressure of the screw and being a loose connection.

I purchase the ETI spades from Hi-Fi-collective.uk, as it is half the price compared to VH Audio.Hope this helps to answer your question.

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

@larry5729 

I wonder if they have done significant blind testing?

I would also be curious to know if I were blind tested to compare speaker cables if I would hear a significant difference? I doubt someone would sit down to listen to a system and say this sounds like you are using Tera Labs or Kimber Cable. I do think buying a decent set of cables does make sense, but not spending more than $1,000. However, $1,000 is a lot of money. The system should I guess cost at least $10,000 to warrant the expense.

https://www.youtube.com/watch?v=HJGw8zwx-6g&t=679s

Problem I have connecting my speaker cable to my ARCAM AVR 550 is I also have my two REL S2 SHO subwoofers connect to right and left channel using the high level connection.  So far, I am not sure I can use a spade connection based on the design of the left and right speaker connections at the back of my receiver.  I think Spades are best for a secure connection.  If anyone is familiar with my ARCAM receiver, I would appreciate your help.  My banana connections work themselves loose over a period of sever weeks and when this happens it takes me a half hour when moving my cabinet against the wall to maintain a solid connection.  I would hate to hog this discussion.  This group is extremely knowledgeable and perhaps someone is familiar with my receiver and can offer some help.

That KLE style banana is what DNM uses. Pretty secure. But the receiving banana hole has to fit really well too.