With copper sleeves over a Puron, I am hearing a slight increase in volume and a more forward presentation. Instruments and voices sound closer to me, and bigger in every sense: height, width, and depth. And yes, more information seems to translate into more detail. This might not be everyone's cup of tea!
It took about 20 seconds of listening before removing a copper sleeve off a High Fidelity MC-0.5 Basic. It was as if the sleeve was a large thick blanket over the speakers. Exactly the opposite of what I am hearing with Puron.
I have the sleeves on two Purons, plugged into a Synergistic Powercell 12. And HFTs on the ends...