I'm gonna be recording my friend's punk band; they wanna record live. All I have is one decent size rectangular room. I'm gonna put the amps in opposite corners, facing the walls. What type of material is good to put over the amps (to stop the sound from traveling as much)? I'm assuming a blanket will work ok and it'll be free. However, if I/they can get some cash, what would be the proper material? Thanks.