 Clearmountain was said to have been one of the first recording engineers to hang tissue paper over the <unk> of the NS @-@ 10 to tame the over @-@ bright treble . Covering the <unk> with tissue paper was said to produce treble @-@ deficient mixes when replayed on normal domestic hi @-@ fi . The phenomenon became the subject of hot debate . Recording engineer Bob <unk> investigated the alleged sonic effects of tissue paper . He found inconsistent results with different paper , but said that tissue paper generally demonstrated an undesirable effect known as comb filtering , where the high frequencies are reflected back into the tweeter instead of being absorbed . <unk> derided the tissue practice as " aberrant behaviour " , saying that engineers usually fear comb filtering and its associated cancellation effects . He also suggested that more <unk> and less random electronic filtering would be <unk> . Newell et al. noted that had the speakers ' <unk> been used in studios , where they are routinely removed , they would have had the same effect on the treble output as the improvised tissue paper filter . 
