The inverter tube is a part of the speaker. It is actually a hollow tube, usually made of PVC material, and some are metal tubes or cardboard tubes. As long as the inner diameter and length are the same, the effect is the same. The inverter tube communicates with the outside space through an exit on the outer surface of the sound box, and that exit is the inverter hole. Inverted tubes are not available in all speakers, only inverted speakers are used, and closed speakers (that is, speakers without any openings in the cabinet) do not require an inverted hole. What is the use of the inverted hole? As the name suggests, the phase-inverted hole is used in phase-inverted speakers to expand low-frequency sound waves. It turns out that when the diaphragm of the woofer vibrates back and forth, it pushes the front and back air to vibrate to produce sound. If it is a closed speaker, this part of the sound wave energy radiated into the box is wasted. Such a waste is really a pity, so some people thought of opening a hole in the box to use the air energy radiated into the box. Use this part of the energy to drive the air inside the inverter tube to vibrate and produce sound, broaden the low frequency range and sense of volume, and increase the total output efficiency of the speaker.
The inverter tube is not arbitrarily opened. The inner diameter and length of the inverter tube need to be designed in conjunction with the physical parameters of the horn and the size of the box, so that the vibration frequency of the air in the inverter tube matches the low-frequency vibration frequency of the speaker unit installed in the box to play a correct role.
