Kef 104.2 grill question

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I always remove my grills as most dont add a significant advantage to sound reproduction.Although my Linn Isobareks performed better with them on,until I changed some source equipment.I would keep them dusted.I usually blow the dust off with a small air compressor but Im sure a synthetic duster would be ok

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!