[mikethedruid]

Yes, "sizing" is a substance like starch that is put onto cloth after it is woven to keep it looking nice and flat. It usually washes right out. It is just a thought, but I wondered if that could be the cause of the impermeability. I have personally never encountered that problem. Another problem might be from the speaker board itself on which the cloth is stretched. If it is de-laminating, that might make a noise like that too. If the noise is not present with the speaker out of the cabinet and away from the speaker board and grill cloth, worst case, make a new speaker board and cover it with something better, then remount the speaker with the new board and cloth.