Just wondering if anyone has had problems with their manual pull-down or electric screens vibrating (and thereby affecting the picture quality) due to a movie's soundtrack? A friend of mine just told me he went with a fixed tensioned screen mounted on the wall for his DLP projector to avoid the screen vibrating while watching DVDs. In all the reviews I've read, regarding front projectors, screens, and home theater in general, I've never heard of this. The only time I've read anything about screens vibrating was when I looked into the possibility of a perforated screen with speakers behind it. Thanks!