In long enclosures such as some sonitube subwoofers designs, standing waves occure in the subwoofers frequency range of 16hz to 120hz. What is the unwanted byproduct of having these standing waves inside the frequency responce range? This site http://hyperphysics.phy-astr.gsu.edu...es/opecol.html shows a standing wave forming at about 50hz when a closed cylinder of 1.7 meters or 5.6 feet is used. I have read that a disk can place some where inside the length of the tube to break up the wave but where to put it? In the middle of the tube or at a 1/3 point.