The terms bipolar and dipolar both refer to speakers with drivers that are fired in two different directions. With dipolar speakers, the two sets of drivers are on the sides of the speaker aimed in opposite directions and are in reverse phase causing a cancellation of sound waves in front of the speaker. This is usually done in rear speakers that are mounted on the wall, where the front of the speaker is aimed at the listening area. This causes all of the sound to bounce off the walls before it is heard. This makes it almost impossible to determine where the speaker is, causing a true surround sound effect.
With bipolar speakers, the drivers are fired in opposite directions, but are in phase causing an increase in bass output. In this case, the drivers are in the front and back of the speaker. Sometimes bipolar speakers have side firing woofers, technically making it a tripolar speaker because it has drivers on three sides. These types of speakers are still referred to as bipolar. There are also speakers that can be used as bipolar or dipolar. In these speakers a switch is used to change from one mode to the other.
Another type of surround sound bipolar speaker is where the side drivers fire at an angle of 90 degrees or less from off the main drivers. This allows the speakers to be mounted in the corner of the room. The side drivers do not need to be identical to the front speakers in this case.
I don't like this kind of speaker too sensitive to the environment of the room, the room must be asymmetric with the thing you put in and with the position of speakers!
Bose 901 that I used work with this kind of speaker but that create a delay from the source, sometime it's good but on classic music it's not the best thing!