Wayne Parham Messages: 18747 Registered: January 2001
Illuminati (33rd Degree)
I like using the metal grilles for speaker that are going to be used in clubs, where they are most vulnerable. They aren't very attractive, but they're tough and don't do much to affect the sound.
Grille cloth stretched over an attractive frame is usually more popular for home-hifi speakers, but you do lose some acoustics in the trade for aesthetics. The material is never perfectly acoustically transparent, and some there is some sound reflected back, which causes response ripples from self-interference.
The frequency and amplitude of the ripple depends on the grille material, and on the distance between grille and source. This is the same thing for acoustically transparent screens for theaters. See the post below for an idea of the ripple that results from a screen or grille: