Wayne Parham Messages: 18786 Registered: January 2001
Illuminati (33rd Degree)
There is nothing that is truly acoustically transparent. If you want the best fidelity, don't use a grille. If one is needed, put it as close to the speaker as possible.
Several materials are made specifically for the purpose, and they aren't that expensive so I would suggest that you use one of them where possible. Not only will it be better in terms of less attenuation, but also in terms of less reflection. Reflections cause response aberrations, which is why I suggest putting the grille as close to the speaker as possible. That will reduce the amount of response irregularities from self-interference caused by the grille.