Is it purely psychosomatic of me... or does your average speaker grille damp higher freq's a little?

It *may* but I doubt it. Once you get up to 40,000 + Hz definatly, but at the freqs we listen too, I dont think so. I know I have never been able to hear anything. Many great tweeters have inbuilt grills. I wouldnt waste anytime worrying about it

The new formats like DVD A and sacd go to 100Khz and at those freqs grill cloth will effect output and so none of the super tweeters have grilles. This means double blind testing or even normal blind testing is very hard, as you cant hide the speakers behind grille cloth to keep them from being seen. Maybe a simple blind fold is the answer lol who knows
peace
Cyberpunky

The first paragraph mirrors my thoughts...but i can almost *swear* that some of the clarity fades out when the speaker grills are on.

I know for a *fact* it makes a difference with some tight woven cloth harmon/kardon desktop speaker tweet covers.

hmm.

i used to have some kicker 6.5" 2-ways, and the tweeters had an adjustable grille on them so you could "aim" the tweeter just by twisting the grille..... the tweeter didnt move at all, but the sound difference was startling

Tweeters, it is certainly possible (depending on the grille etc). Midrange - probably not (unless it happens to be playing very high - much higher than most car audio midranges).