dipole loudspeaker
The dipole speaker principle works with two speakers. Both speakers emit the sound in different directions and also work out of phase. One speaker emits the sound to the front, the other to the rear.
This technique creates a diffuse sound image, which is used especially for surround sound. Depending on the arrangement of the two speakers to each other, one speaks of the dipole or bipole principle. The latter is the case when the two speakers are arranged in opposite directions. In this constellation, one speaker radiates to the front, while the other radiates the phase-shifted signal to the rear. Theoretically, no sound would be heard on the axis between the two loudspeakers, since the sound signals from both loudspeakers compensate for each other.
In practice, the sound from the rear-firing speaker is reflected off the walls and arrives at the listener with a time delay, causing the diffuse sound impression.
Dipole speakers are used in surround systems and are specified in the Tomlinson Holman Experiment( THX).