my understanding is that the mandalas have a higher intensity the larger they are. Just imagine the intensity of a billboard-sized mandala
I assume the energy would propagate in a larger area, proportional to its size, around the mandala and would be felt by people walking by it, even those who do not believe in such things
It would be an interesting idea to do this on a billboard on a busy city street or highway, with the negative ion creator or attract positivity.