Soldered VS ...everything else

All solder pretty much is eutectic. All eutectic means is that it melts all at once at a temperature lower than its constituent parts. I am not aware of any common solders that do not do this.

Tin-Lead solder melts at a lower temperature than other solder types, and as well, it tends to wet components better than other solders. It is also less brittle. That is probably why you like it. The wetting part can be fixed with other solders with better fluxes to some degree.

Isn’t it encouraging that future is wireless?

Until then, no solder, bananas.

If you can, connect the clean bare wires to the speaker terminals. All connectors, paste or any applied coating will degrade the signal.

But, if that is not possible make the connection with the best metallurgy available. No solder, paste, etc. Crimping would be the best in my opinion. You want to minimize any substance between the connections.  

ozzy