Depends on the grill, obviously. Some fabric is so light and open that it has no effect. In some cases the speaker system may have been "voiced" with the grill on, so its removal will brighten the sound, perhaps excessively. Subwoofer sound penetrates walls, so a grill cloth should be no problem.
Your cats are badly behaved. You should train them. My only problem with cats, when we had one, was that it would climb up my Magneplanar speakers and sit on the top. Fortunately there was enough clearance between the grill cloth and the diaphram so that no damage was done. I trained the cat.
Your cats are badly behaved. You should train them. My only problem with cats, when we had one, was that it would climb up my Magneplanar speakers and sit on the top. Fortunately there was enough clearance between the grill cloth and the diaphram so that no damage was done. I trained the cat.