The grills of the speakers generally have acoustically transparent fabric which does not change the tonal characteristics of the sound. I owned maggies for six years and I remember I had to take off the cloth for checking the inside of the speker for fixing the wires on the mylar and I did listen to them without the cloth in place. I could not make out the difference. I was a bit surprised since I expected them to sound different. Later I did read bout it in some brochure of Magnepan and sure enough they had mentioned it clearly that they use acoustically transparent fabric.
Paradigm's state in their catalog that the grills should be on when evaluating their speakers (Paradigm Reference Studio 40 v.2).
If the speakers come with a grill which is meant to be easily removed and put back on, you actually have an option there, use it the way you want and what suits your own ears. Wanna play it safe? Go with what the manufacturer says, they are usually right!
Paradigm's state in their catalog that the grills should be on when evaluating their speakers (Paradigm Reference Studio 40 v.2).
If the speakers come with a grill which is meant to be easily removed and put back on, you actually have an option there, use it the way you want and what suits your own ears. Wanna play it safe? Go with what the manufacturer says, they are usually right!