I just received a sample booklet for GOM FR701 fabric and noticed that the NRC rating is 0.00 to 0.05. Presumably the 0.05 is at high frequencies at which point 5% of the sound hitting it will be absorbed. Absorption coefficients typically span the frequency range of 125 Hz to 4 kHz. If the NRC is 0.05 at 4 kHz, I can only imagine that it will be worse at even higher frequencies. I am trying to design my home theater so that it has a fairly even RT60 over the audible frequency range and was not planning on having to take the fabric into consideration. This has me questioning whether or not I want this fabric covering my walls and especially my speakers. The samples I received are too small to cover a speaker for checking its effect on high frequencies. Has anybody noticed any negative effect on the sound of their speakers after placing them behind this fabric?