In the mid 60's, and early 70's, when we had a problem with bad room acoustics, we made a frame out of light weight aluminum strips, and draped or hung light blankets, a couple, or a few feet in front of the amps, or drums as needed. This acted as a filter, or a sound damper. As stupid as it sounds, it worked. Same amps, drums, guitars, and basses. Just augmented the sounds. It worked in studios too.