Speakers sound better without grilles?


I've noticed that my NHT SuperOnes subjectively sound better when i remove the grilles. Specifically, the off axis sound from the tweeter seems better. This is most noticeble if i'm sitting in between the speakers very close to the speaker wall (since the speaker drivers aren't pointing directly at me) The highs just sound clearer and brighter. Is this normal? Also, are speakers supposed to have the grilles on or is just for looks?
eighthcircuit
Depends on the speakers, but certainly many speakers do sound better without their grilles. Some manufacturers explicitly recommend removing the grilles for serious listening. Others (e.g., Paradigm) design their grilles to actually enhance dispersion - my Paradigms definitely sound better with the grilles in place. For most speakers, grilles are just for appearance.
LS3/5a's are supposed to be listened to with the grills on since it was designed that way. Some cannot tolerate listening to speakers with the grills on and invariably will remove it due to habit irrespective of what the speaker builder says.
It is rare that a speaker sounds better with the grills on. One exception was a pair of NEAR model 10M I believe; the grills actually tamed the harsh metal tweeter.