Kef 104.2 grill question

I purchased a pair of the Kef 104-2 speakers In the early 80’s and still have them. I use them on a regular basis. They sound no different without the grills and the exposed port causes no issues. If you are afraid of dust, every few weeks use a feather duster and 
very lightly rub it over the drivers. Enjoy them for what they are. Good sounding classic speaker!