Poles Apart Page 2

But opinions differ sharply when it comes to the surround-channel speakers. One school of thought argues that surrounds should provide the same precise imaging as the front speakers, while the other argues that the imaging from the surrounds shouldn't be precise at all. If each school had a football team and they played each other, it would be a great game.

The first school (let's call it Monopole U.) believes that the front and surround speakers should be the same. Moreover, because accurate imaging is desired from all of the speakers, they should all be monopoles. Chances are, your front speakers are monopoles (you probably didn't even know that you were an alum of this school, did you?).

The second school (Dipole U.) believes that surround speakers should be specialized designs that don't match the front speakers, at least in terms of design and driver configuration. The dipole design, which reflects the sound from room boundaries, dispersing it all around the listener, is excellent for providing ambience and cues that recreate a sense of acoustic space, but at the expense of precisely placing individual instruments and sound effects.

Sound Decisions Opting for one kind of speaker over the other on theoretical grounds, though, lands you squarely in the surround sound dilemma: the surround channels of movie soundtracks tend to be designed primarily for diffuse effects that create a sense of space, while many music recordings are mixed with specific instruments or vocals placed firmly in one or both of the surround channels. Filmmakers use the surround channels primarily for general sound effects (like helicopter flyovers) and specialized ambient sounds (like the clanks and drones of a submarine interior) to help envelop the listener in an artificial reality. Since film soundtracks are mixed to work best in movie theaters, where several surround speakers are used and people are seated throughout the space, the sounds placed in the surround channels aren't meant to be localized. Because of this, recording engineers almost always use dipole surrounds to mix movie soundtracks.

Engineers tend to be more ambivalent when it comes to surround sound music recordings, like the ones found on DVD-Audio and Super Audio CD releases. When the intent is to simulate listening in a concert hall, as with most classical music, the surround channels will mainly contain reverberant hall ambience. With pop recordings, however, many engineers see the surrounds as an extension of the palette offered by the front channels. Instruments are often placed in the rear and are meant to be localized in the same way as in the front. So it shouldn't come as a surprise to find out that most surround music mixes are done using monopole surrounds.

Given all of these variables, and two dramatically different approaches to surround sound, what's an audio aficionado to do?