Transmission line speaker: A similar mode of operation as bass reflex boxes also have so-called Transmission-Line speakers on. These are also characterized by an externally visible sound outlet opening, which is usually larger and - as a rule of thumb - roughly the size of the membrane surface of the bass speaker. Characteristic of the internal structure of such a sound transducer is a tube with an opening leading to the outside, at the other end of which is the actual driver.
