Originally Posted by craig john
Bipoles offer the best compromise between dipoles and monopoles.
Dipoles have a "null" in their dispersion pattern that faces the listener. They are intended to be mounted in only one location... at 90 degrees to the listener, (directly at your sides.) In other words, you get no sound directed towards you. You only get sound directed towards the front and rear walls. This provides a very diffuse soundfield that adds ambiance. They work great for content that is intended to be ambient. However, for content that is intended to be localized to the direction of the speaker, (many sound effects in movies are this way), they don't work well at all. Dipoles are basically a holdover from the old ProLogic days, when the only content sent to the surrounds was ambiance stuff extracted from the front channels. In current SS technologies, (DD, DTS, and the lossless codecs), the surround content can be discreet, and sound mixers can use the surrounds to add directional cues. To reproduce those sounds accurately, one needs a "directional" speaker.
Monopoles have a direct, localizable dispersion pattern. They are not diffuse sounding. For content that is intended to add ambiance, monopoles can work, but dipoles work better. For content that is intended to be localizable to direction of the speaker, monopoles work much better than dipoles. They can also be mounted in more positions than dipoles, as long as they're aimed at the listening position.
Bipoles are the best of both worlds. They have a 180 degree dispersion pattern. For content that is ambient, they project sound to the front and rear and add ambiance. For content that is localizable, they project sound directly at the listener and are directional. They have far greater placement flexibility, and they don't necessarily need to be aimed at the listener to work properly.
The Klipsch WDST design uses 2 symmetric horns mounted at (approx.) right angles to each other. Both horns have a wide, almost 180 dispersion pattern. They spray the front and rear walls with sound for ambiance, and they direct sound towards the listener for directionality. Here's what Klipsch says about WDST:"Exclusive Wide Dispersion Surround Technology (WDST) enables surrounds to reproduce localized and ambient sounds with unlimited placement flexibility."
I see no downside to those surrounds.