I stop giving my experiments results here long ago except in general way of speaking because instead of welcoming each one experience with an inquisitive and curious mind many people gave sarcasms or common place engineering explanation ....
The same people often gave their money in gear upgrade not knowing how to improve their audio at no cost...
Yes i used copper foil and numerous others basic facts and basic no cost devices...
And after their upgrade they are convinced by (consumers bias) suggestion in the same non controlled room that all is better... Then they read about someone making a low cost experiment and they throw sarcasms about their tin foil biases about S.Q. value...
Most audio thread are useless because instead of experiments they spoke about gear...
It is once your gear is bought that begun the audio journey not before or not till an upgrade... It is after you had bought the gear that you must learn how to put them at his optimal unknown working level with mechanical,electrical and acoustical embeddings controls method and devices... Including copper foil....
Congratulation to the OP for his courageous thread at best facing ignorance, because no ears/system/room react the same way to any change or at worst contempt by programmed mind with no need for any experiment ...