You can certainly hide the speakers behind fabric if you choose. However, as Ethan said, while GOM is transparent enough for treatment covering, I wouldn't put it in front of my tweeters. If you want something like that, you almost need to go with something that is designed as a speaker grille cloth - much thinner and more transparent than GOM.
Now, if you have speakers/processor that has a THX compensation for sitting behind the screen, this CAN help overcome SOME of what the thicker fabric would block.