Are these blankets by my speakers good for acoustics ?

Hard walls behind speakers tend to encourage an echo.. So putting something in between the speakers and the wall that absorbs sound is a good idea.. I have seen Book cases used a lot behind speakers .. The paper books absorb sound and work to cancel out the echo..

I have seen hard core audiophiles turn the books around in the book cases so the binders are at the back.. This has the best results..