How do they work?
These are the loudspeakers we are all used to seeing and hearing 95% of the time and we will have at least 1 pair in our homes and most likely several in our modern cars.
They have all the drivers on one face of the enclosure and are known as direct radiating or monopole speakers.
These can be used anywhere in your home cinema. You will get the best and most precise surround-sound performance when all of your speakers (front, center, and surround) are direct radiators.
Some home cinema fans (the boffins at THX included) prefer bipole speakers, these speakers have drivers on two faces, opposite each other. They are designed for side/rear surround speaker applications to push and spread sound along the walls, which gives a more diffuse, enveloping sound than direct radiating speakers.
Bipole speakers fire their cones to the front and rear at the same time and in phase. In other words, the cones go out or in together, in the same direction (both out or both in) and at the same time.
Generally manufacturers also combine a bass driver between the two effect units in order to give even greater depth and presence to the surround system.
Effects speakers (as they are also termed) are also available for custom installations, either for in-ceiling or in-wall, maybe both!
These speakers also have drivers on two faces, opposite each other and are again designed for side/rear surround speaker applications. Dipole speakers are out of phase with each other, when one side’s drivers are pushing out, the other side’s drivers are pulling in.
Did you notice any difference in configuration, placing of the driver units, between the two example speakers?
No - you normally won't as most manufacturers use the same placement and then incorporate electronics to make the units to be switchable between Dipole and Bipole.
From this they emit sound in two different directions creating a diffuse, non-localised sound, but the drivers are out of phase, which creates a dead zone in the listening area that makes the origin of the sound even harder to pin-point.
Although the electrical phase in bipoles and dipoles is different, the basic physical construction of bipoles and dipoles is similar. So look for speakers that are both bipoles and dipoles. Most of these speakers have a switch that lets you switch the mode they operate in. Some people prefer music played back through bipoles and movies through dipoles, and these speakers let you make that choice on-the-fly.
It is clear that bipoles and dipoles all provide a more diffuse surround-sound experience. There’s nothing wrong with this, and in some cases it can enhance your experience. However today’s surround-sound soundtracks are generally recorded and mastered using direct radiating speakers and the discrete surround-sound channels with Dolby Digital or DTS (or their higher-resolution counterparts such as Dolby TrueHD and DTS-HD Master Audio).
A number of manufacturers produce complete home cinema loudspeaker kits that incorporate a combination of Monopole and Di/Bipole in order to get the best overall effect and to cope with the different surround standards mentioned above, including THX of course.
Our experienced sales and support team are always available to provide further information and advice on what speakers, or combination of, will suit your particular situation.