Proac D48R

What you are describing is relevant for almost any speakers I called it ’screening’ affect ,when you are hearing the speakers with the grills on it like you are putting a screen between the twitters and drivers to your ears .The grills are for to protect your speakers from dust or potential damage to the speakers’ components.

This was not an issue when the speaker was new. After 1 1/2 years I notice that any small change to the speaker placement or grill makes a big difference.

Vandersteen and a few others are the only ones I know of who voice their speakers with grills on. I have Vandy Quatro's and the grills have never been off of them and never will be as long as I own them. lol.  I kind of like that part. I have owned Proac's for years and always had the grills off.  Everyone I know who sells them have told me to keep them off.  That's why their beautiful baffle finish is important, lol.

hmmn, for my D48Rs,  I keep mine on but I haven't done a comparison against them with them off.  I will now. 

@kclone ,
Good to know that you are still hanging on to your ProAcs. One thing to know - you have (probably) NOT heard the full potentials of these loudspeakers. I recently introduced the Inakustik power conditioner and later a Inakustik power cord in the system. And this positively transformed my listening experience.