Part XXIV: Transmission-line enclosures

7.19. Transmission-Line enclosures

General description

A transmission-line enclosure has a duct or tube between the rear side of the loudspeaker and an opening to the outside world, which is usually folded to save space. Sound is radiated both from the front of the loudspeaker and from the opening. Unlike a bass-reflex enclosure where the dimensions of the enclosure and port are usually small compared with the wavelength, the duct is long enough for it to introduce significant phase shifts at low frequencies. If the length of the duct is one-quarter of a wavelength, a small movement of the loudspeaker diaphragm creates a large movement of air at the duct opening. Thus, the enclosure causes a large ...

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