What is special about transmission line speakers

The design idea of the transmission line speaker is completely different from the closed box or the inverted box. It uses a 1/4 wavelength transmission line to achieve the purposes of absorbing the resonance of the unit, suppressing the displacement of the diaphragm, and expanding the lower limit of the low frequency. Transmission line speakers have the following basic characteristics: a long pipe (transmission line) is connected behind the woofer. The length of the pipe is 1/4 wavelength of the unit's low-frequency resonance frequency (or a slightly higher frequency). For the sake of dressing, the pipe Usually folded inside the box, it looks like a labyrinth; the cross-sectional area of the transmission line connecting the speaker unit is at least 25% larger than the radiation area of the unit, and then gradually becomes smaller until the exit of the transmission line is just equal to the radiation area of the unit diaphragm; Damping characteristics such as wool or glass wool are laid in the transmission line. Transmission line speakers have deeper bass than airtight boxes and inverters. However, some people represented by Martin Colloms, a well-known British speaker expert, believe that transmission line speakers are more difficult to avoid sound staining caused by transmission line resonance.