When you use the grills as a tone control to soften or tame high frequencies,that is something I did long time ago and it does work slightly but you are robbing yourself from better performance by having the grills on. Years ago, audiophiles didn’t have the amount of recent tweaks we have today. Many audiophiles, years ago, were restricted to tube rolling and component swapping to get that “correct sound”. Today, we now know certainly that cables, isolation point, tubes, room treatment, etc. make a significant difference. So one should tweak the hell out of the system with all the many tweaks we have available to get the tonality and clarity right without having to use the grills as a “tone control”. I really believe so strong in removing them from my own experience and the performance I have achieved from my systems. The only good reason I could see keeping them on would be that the speakers/drivers look very bad when the grills are removed or dealing with children and pets at home. But if you can live with them off, the sound is much more involving.
