Back in the Eighties, the default POS nearfield monitor speaker for checking how mixes would probably sound on domestic sound systems was the Yamaha NS10. For some reason, it became fashionable to remove the original fabric covers and then hang a sheet of tissue paper over the tweeter moulding. This practice became the accepted wisdom of the age. I recall no published literature demonstrating or quantifying what difference, if any, this practice made to the final sound?