OMG, just removed my speaker grills and the sound just opened up to a new level!

A good rule of thumb. When you're not listening keep the grills on.
When you are listening take them off.I had a pair of Daulquist 20 removing the grill made them look like a science project. The sound was Incredible

From the early days the ADS speaker line had really nice metal speaker covers, especially for the time. Not sure the difference in sound on or off.

*S* Personally, sans grills entirely....Lucifer 'n I get along just fine....🤪

...although...."The Grill Clapper!  *clap*  Grills off....*clap* Grills on!

Now available with AGP!  Automatic Grille Protection!

If your speakers are approached by Any lifeforms, the grills are automatically deployed, covering your investment!"

(Not sold in stores.  No liability for any and all injuries caused by AGP; the system is designed to be Very Positive in it's function....)

My Klipsch Heresy IIIs sound a little more "open" with the grills off (this could be imagined, but so what?) but look better with 'em on...since the grills are held on by magnets I try to remember to put them back after an "active" listening session as since they're tilted back they collect dust on the horns and the bottom ridge of the woofer. The dust refracts sound and reduces the accuracy of the speakers by .000243%, which can make violins and lap steels sound orange-ish. The best way to clean the horns is to take the speakers outside and blast the horns with a power washer...sure, it warps the cabinet and the horns don't work for a few days, but the dust is gone.

I just removed the grill from my Cheese Sandwich Model 100 speakers.  They are less tonally dark, and softer.