I agree with Kal. It depends on the speaker, as well as listener preference.
Until recently, I never listened to my speakers with the grilles on. Then I tried it as an experiment. As expected, there was a slight diminishment of perceived resolution. But unexpectedly, there was also a slight improvement in imaging and tonal balance. So now it's grilles on (except for the tweeter grille, which remains off).
The moral of the story is that experimentation is the Order of the Day.
Bryon
Until recently, I never listened to my speakers with the grilles on. Then I tried it as an experiment. As expected, there was a slight diminishment of perceived resolution. But unexpectedly, there was also a slight improvement in imaging and tonal balance. So now it's grilles on (except for the tweeter grille, which remains off).
The moral of the story is that experimentation is the Order of the Day.
Bryon