On the subject of modern grill cloth and treatments
two issues
diffraction at the edges and absorption
competent ( well IMO ) engineers design a frame that is acoustically integrated with the baffle - optimizing for flat response or other variables, as stated some may voice or engineer for grille on or off.
Cloth is not a uniform absorber period
for the record, run the brother in laws loaner L-100 with the ancient grills off....
two issues
diffraction at the edges and absorption
competent ( well IMO ) engineers design a frame that is acoustically integrated with the baffle - optimizing for flat response or other variables, as stated some may voice or engineer for grille on or off.
Cloth is not a uniform absorber period
for the record, run the brother in laws loaner L-100 with the ancient grills off....