Easy free tweak -- dealing with RFI/EMI -- try it and see?

With some Ciamara credit available I thought I'd try the Stillpoints ERS paper on the insides of my fuse box and Torus wall transformer to see if it helped improve things in my system. Treating fuse cabinets is a fairly well known application of this product which is designed to absorb stray RF and other electronic nasties

Well here I was tweaking away and I thought, golly the system sounds really clean and open and I haven't put the paper in yet -- I assume it will be even better with it!

Imagine my surprise to discover I'd been listening to the system with the fuse box/panelboard cover open! Turns out one of the best things to do with EMI and RFI may not be to enclose it in a metal box in the first place 🤓

And actually with it closed, with or without the ERS paper it sounded much more closed in, with a loss of low level detail

Same went for the door on my Torus transformer -- from now on I'll leave it open for serious listening -- there is a bit more audible transformer hum but as it's in another room this is no big deal

Anyway this is a dead easy free tweak so give it a try -- you may like the results
Bingo! The magnetic field produced by the door is bad news. It's got nothing to do with RFI/EMI.
I think you are missing the point @randy-11 While an enclosure may form a Faraday cage the EMI/RFI is enclosed and reflected back into the power lines and down into the rest of your system which is the problem so what we actually want is to let it get away without polluting the power to the system
@geoffkait I'll accept that the door is magnetizable so that's a plausible factor ... anyway love to hear what experience others have one way or another
wrong folkfreak - that is not how it works

there is a simple explanation in the wiki - pls read it
Sorry Randy maybe I missed it - my EE degree was thirty years ago 😕 why would opening the door help?
maybe you are letting out Maxwell's Demon
Ghosts in the machine now, eh?
If you are indeed hearing a difference with the electrical panel cover open I don’t think it is because of EMI/RFI.

geoffkait may be on the right track with his theory about the magnetic field, don’t know for sure. There is a magnetic field that extends out around the current carrying conductor internal parts of the breakers. That would include out the breaker handle front of the breaker. Every other breaker down each side of the panel is on the opposite leg. (L1, L2, L1, L2, L1, L2, and so on). I would think the magnetic fields, of breakers with connected loads, would somewhat cancel each other out. Don’t know for sure. Introduce a ferrous steel cover in close proximity of the front of the breakers may have some effect on the magnetic fields of the breakers. Again, don’t know for sure.

You really need to run ABX listening tests to prove what you are hearing is real, and not just imagined. I suggest you have someone open and close the door for the ABX test and then you listen for differences. If you can correctly identify X  90% of the time then you are indeed hearing something. The why?

You should run at least 10 or 12 trials.

For the same reason all transformers, especially those big honking output transformers, should be wrapped with low frequency high permeability mu metal. For very best results wrap the transformer twice leaving a 1/4" space between the sheets. As for the ERS stuff I’d be very careful with it while experimenting. Listen for the sound becoming wooly or weird sounding. Wooly, bully. I recall distinctly hearing the ERS paper hurt the sound when a sheet of it was sitting on a coffee table in the listening room. I also heard it hurt the sound when it was moved to another room. I'm not hot doggin' ya.
EMI and RFI is almost all, "through the air" interference, and not significant in power lines.

Unless you live near a hospital, industrial park, or have motors turning off and on, on your power line. Motors that "freewheel" will generate noise back into the power line.

Opening and closing the door on the breaker box and hearing a difference is in your imagination!
I removed the cover from my breaker box some 10 years ago as the this reduces the surface area of shear to populate and then travel on the solid core path to the high fi. transformers. Tom
I had a group of friends over to witness the benefit of removing the cover..on and off and then staying off.... Easy call for them to make as to the sonic benefit when gone.The cover is not a shield of emi/rfi but rather a collector and converter of other detrimental wave types. Tom
I know that the field surrounding the power lines is strong enough to carry and transmit 5TB of data at an incredible rate because an AT&T tech told me they've been doing it for some time now to explore other ways of transmitting data without resorting to new construction.

Now, if the field surrounding the power lines are that strong, one can easily imagine the effects it can have when it gets down to your breaker box. There's so much going on that's yet to be fully appreciated.

Now, as for EMI/RFI I use a Schumann device near my listening spot. I can reach out and unplug it at will and it's easy for me to hear the difference. In my apartment there's easily 30 hot spots of Bluetooth and WiFi competing for attention and two side of it rum parallel with power lines, polluting the whole place with electronic smog. Just because you can't see it doesn't mean it isn't  there.

All the best,
Yes, in a digital chain airborne EFI can be a problem - even routers hunting periodically can cause kvetchng problems.

OP needs to do some blind testing as noted above
RF is insidious, pernicious and toxic and permeates almost everything. Even though as we now know, it’s really photons, but photons that can travel through solid objects. RF gets into the local house wiring via any number of paths, including, but limited to, through unused power cord plug prong holes in the listening room and every room of the house. Not to mention the ubiquitous microchips in modern electronics like CD players generate gobs of RF. All local cell phone towers, satellite TV, microwave towers, microwave ovens, TVs, air purifiers, etc. generate boatloads of RF. RF is like Chickenman (he’s EVERYWHERE!).
Re @randy-11 and @geoffkait I've found good results from seriously addressing RF pickup in my digital chain by capping all the unused inputs. There are a boatload of BNC connections on a DCS stack so this ends up being expensive but the cumulative effect is noticeable. Also as Geoff suggests closing of all unused power outlets is also worthwhile. 

Anyway spent end another hour this morning experimenting with the doors of my panelbox and isolation transformer open or closed. Still prefer them open 😀
I just opened the door on my breaker panel that is in the garage and I did hear difference especially in the separation of the highs/cymbals but also a slightly wider soundstage. Very interesting as all the unused outlets in the system/listening room are capped as well as all unused component inputs are either capped with shorting plugs or non-shorting caps.