Please report your results.
I wrote about the results in my 1st post. Based on cheap plastic/nylon pure copper or even antique copper one noise floor is easily heard as being lower, the bass impact was vastly improved and deeper, midrange detail better, and highs more detailed yet smoother with a greater focus and imaging. All due to like anytime you reduce noise. I have had them on for a few years almost and in fact, only tried the white cheap ones the other day just to see what I would hear, it took less than a song to know boy they really damage the sound. My wife said turn it down or off, that sounds horrible, what are you doing, I said I change the wall plates, she said people will think your nuts, but put it back the way it was, I did and she walks in and said that is crazy. Well with all the wifi, and routers (5G) mine affect my garage door opener and my PC speakers had noise big time when I got it, that is how powerful the noise to electronics generates and impacts, not to mention the old school of RF/EMI. Basically, it is blocking noise where the power cord is plugged in, it's a barrier in and out. Much like Marantz and Sony and others have used in their better gear over the many years, copper shielding. That is what gave me the idea to look for pure copper wall covers and for $10.00 I said give it a go, if they don't work they look better than white plastic, so zip to lose, and I was really surprised with the results. This is why my M3s have not had some sonic issues some have had, with the cheap white ones I heard those issues, but it is not the speaker's fault it is what they are receiving and just reproducing what is coming from the system, and it's not the gear as much as the noise coming from the outlets we plug our gear into. When I put the white ones back on the ac outlets and if I heard no deterrent then I would know it was my error but that is not the case. Had my wife sit and listen to our video system and a movie with good effects and a bottom end, I took out the wall plates and installed the covers with the pure copper, turned everything back on, and told her to listen, 1st thing I heard was dialog was fuller, then the special effects went off and my wife turns it down that sounds so much louder now and the subwoofers are so strong now, only change the 2 wall plates, and on both systems (audio and video) I have power conditioners and the wall plates still make hearable benefits.