I have some Original Large Advents I am putting together. Does anyone know what the spec would be on that cloth? Did it change any when the NLAs came out? There would seem to be 3 challenges to replacing the grill cloth: 1) finding something that has no acoustical impact 2) getting the right density of cloth (tpi) and material 3) having backing material I would guess correctly taking care of 2) would then result in 1) being satisfactory.