By the way I improve the schumann resonator another times and put it to another level for the impact... I use stones on the center spot of the generator(Shungite +Herkimer) connected by a very ultra thin copper cable, like a hair, connected to the other stones of my stones grid...I must say that the schumann resonator (a Chinese one 20 bucks) are almost the most astounding tweak I ever made, very different impact than the Helmholtz resonators but not less impactful on the contrary, and perhaps better than a new amplifier or at least like a very costly new one...
I had no words...Buy one and if you are not astounded, the reason is your system is not cleaned of vibrations or interference, nor your room adequately treated...