Subwoofers - Grille off or on?

I don't know the answer but perhaps Tpreaves objected to the word "always" in the statement.

It could be some speakers are designed to be accurate with grills in place and removing them may be pleasing to some and worse for others.

Experiment and decide for yourself is not a bad suggestion either.

Just which speakers do you have in mind? Are you saying that the ones I have listened to really sound better with them on? What I said was that I had never heard one sound better. I have not heard all speakers and I doubt if you have heard the ones I listen to. My Mini Utopias did not COME with a grill, did Focal screw up their sound? All the grill can do is attenuate the treble, do you want that done? The only really transparent grills ever made were the old foam ones like JBL use to use, effective but looked cheap. Even the Quads were considered to sound better uncovered.

Stan some speaker grills have built in tuning material for the tweeter for example. If a grill does in fact attenuate the treble some speakers may infact be made with a hot tweeter to account for the grills. Its matter of opinion and personal choice but it is not fact.
I dont like the look of speakers with grills off, reminds me of college kids for some reason but I also dont hear a negative in sound so that works for me, others like them off and thats cool too.

I used to think speakers sounded better with the grills off, but I've changed my ways. Now I like the sound better with grills on, but I find it hard to believe it would make a difference on a subwoofer.

You nailed it Albert.The "always" makes the statement null and void!!