Originally Posted by TStubb
Ok, so there are not alot of bipole speakers around anymore it appears. There are some models out there that have dual opposing tweeters like the Klipsch R-5650-S II as opposed to the Def Tech DI 5.5BPS's that have dual opposing woofers. Would having just the opposing tweeters versus having two sets of both drivers like the Def Techs but just as good? Is it mainly the higher frequencies that I would benefit have more dispersion or would the benefit be greater with a wider dispersion of the full range like on the Def Techs?
It may be helpful to think of a binary system "light bulb" analogy, where frequencies are divided into two subsets, low and high frequencies. The low frequencies would be analogous to a flood light, whereas high frequencies would be analogous to a spotlight. The floodlight will illuminate a wide, broad area, with similar light intensity sent in all directions. The spotlight will focus the light into a small beam, strongly illuminating a small, focused "spot", with less energy sent outside the beam. Reflected light will dominate the illumination of anything surrounding the focused beam.*
In a bipole speaker, you can take two "spotlights" and shine them in opposite directions, and get broader coverage over a larger area, in an attempt to match the broader dispersion of the flood light. It is important that the two spotlights be "in phase" with each other, and with the floodlight to ensure the result is additive, instead of the cancellation that would occur if the two were out-of-phase with each other, (as in a dipole.) An added benefit of this alignment is that the coverage doesn't change appreciably as the listening position changes. If the bipole is slightly in front of, directly to the side of, or slightly behind the side-plane of the listener, the same dispersion will be heard.
(*Now obviously, this is a massive over-simplification as soundwaves can't be simply divided into just two parts. In the real world situation, dispersion is more of a progression, with dispersion decreasing continuously as frequency increases. Therefore, the analogy is not perfect, and is for "illustrative" purposes only, (PI)
There are many manufacturers of bipole surrounds: Def Tech, Klipsch, Triad, Atlantic Technology, Sonance, SVS, Focal, Polk, and many others make bipole surrounds. Dolby actually recommends either bipoles or monopoles, but NOT dipoles, for use in Atmos systems. Bipoles have the advantage of adding more reflected sound than monopoles, so they can provide more "spaciousness" than monopoles. OTOH, monopoles can be more directional than bipoles, so they can provide more discreet sound localization when the content calls for it.