Part Two - The 10.2 Room
The basic underlying principles that drive this new 10.2 standard are based on an enormous amount of supporting data, and some elegantly performed experiments, the conclusions of which I will do my best to simplify and summarize here. Many of these are not new concepts, but I will do my best to reiterate them in a logical and reasoned way so that I do not confuse those new to these particular surround sound concepts by misstatement of fact.
1) The front half of the room is more important than the back half!
What is perhaps the most repeated mantra I heard during my visit was how the decision to add 2 rear channels when 7 channel sound offered itself as an improvement over 5 channels is according to Audyssey, a serious error. IF these extra channels are available, they should be added to the front, NOT the rear. Why? Human hearing has far better spatial acuity in the front of us than we do behind us. According to Tom Holman, we can resolve auditory spatial information to about 1 degree in angle in front of us from right to left, (Horizontal plane) and about 3 degrees in height (Vertical plane). Both of these sensitivities are far greater than what we have for sounds coming from behind us. Hence Audyssey's preference of multiple channels in front and sides, and one required for rear channel sound.
2) Width is more important than height!
Width is crucially important in placing instruments and recreating acoustical space. Concert halls with side walls perpendicular to the stage are considered by experts on the subject to be acoustically superior spaces to fan shaped halls. One of the reasons here is the importance of the early reflections from the right and left side walls perpendicular to the stage. In the "fan shaped" concert halls, the splayed side walls did not support the same kind of early reflections and are one of the main reasons these halls are not judged as good by the experts. To quote Mr Holman, "it is known in concert hall acoustics that the first side wall reflection is the single most important reflection direction, it sets the auditory source width... Channels constrained to plus/minus 30 degrees are too narrow for that". For this reason, the DSX standards (7.1, 9.1 and 10.2) support a left wide and right wide channel at plus/minus 60 degrees to reproduce the kind of side wall reflection you would hear if you were seated in a great concert hall. (Note: Those who recall Audioholics' original article on 10.2 may note that the front widths were at 55 degrees, not 60 degrees. According to professor Chris, this small adjustment was made because the difference between the two angles was minimally audible, and "60 degrees is easier to eyeball").
3) If you pan front from the front to the surrounds, it is nearly impossible to get the sound source to appear to go behind you with only the two rear channels at 110 degrees. For this reason and others, 10.2 employs a center back channel, located 180 degrees relative to the listener.
4) Because height is also an important element in recreating acoustic space. (Not as important as width, but important nonetheless) a pair of channels are added at 45 degrees off the center front, and 45 degrees high relative to the listener. A sound source with height can best reproduce reflections from a high ceiling, adding an additional dimension of space to the recording. We were able to listen to some choral music during the hour or so spent in the USC multimedia room, and the high speakers made a dramatic difference in the source height and sense of space.
Audyssey's Surround Sound Room
In summary I would like to add one small note. We have all had experiences with surround sound we find both enjoyable and memorable. They all require one common element, musical or dramatic performance. There is little doubt in my mind that these additional channels will not only improve the spaciousness and immersion of the surround sound experience, it will allow greater musical expression by allowing both visual and musical artists to more fully engage the listeners sense of space and direction in the musical or theatrical performance. When all is said and done, this is one very important aim of both Audyssey and 10.2 sound.
What does this all mean for consumers? A quick check of Audyssey's website, which is an excellent resource for information about surround sound standards and practice will reveal that there are already a great many commercially available products which employ Audyssey technologies like MultEQ XT, dynamic EQ and volume. Currently there is only one receiver employing DSX, the Denon AVR-4310CI.. DSX is a scheme for deriving wide channel information from the front channels. The ideal situation would be recordings which encode discrete multichannel sound of course, but it is likely to take years before the recording industry adopts these standards for most recordings of music. Fortunately, ever increasing media density and improvements in bit-rates available will receive pressure from the movie industry for more channels. While audiophiles are interested in higher sampling rates (96 kHz over 44.1 kHz) and greater bit depth (24 bits over 16 bits) extending dynamic range and available frequency response, Audyssey is more interested in adding additional discrete recording channels to the sound for an improvement in the ability of listeners to localize sound in space.
The one big question mark about pushing the confines of audio into truly discrete 5, 7, 9 or even 10 channel sound is the question about the availability of recordings with this discrete information. While Dolby, DTS and THX all have surround sound standards with 5, 6 and even 7 discrete channels, our selection of media is limited to DVD's. While the number of movies with this multichannel information continues to grow, audio only media seems to be stuck in the 2 channel format for the most part.
Editor's Note:
We feel obligated to say that while, in theory, 10.2 seems to be the current epitome of surround sound we have no illusions that this will necessitate or translate into better sound for the average consumer. In fact, it is likely that it will result in quite the opposite. As manufacturers scramble to include more and more speakers for the same price point, quality is almost certain to suffer. This goes double for the front of the room - in which most houses top off at 8 ft ceilings, rendering height channels less useful. The average consumer spends less than $1000 on surround sound and figuring 10 speakers and two subwoofers into that mix is going to lead to some interesting results to say the least. In the final analysis, it is likely that more will not equal better. For the most part we still stick to the axiom that better is better. As for 10.2 - this is likely to get its best reception from high-end cost-no-object theaters,
As it did back in the day when 5.1 changed how we listen to music in the home, movies will be driving the next changes in audio. Our 5.1 channel receivers of today are as sure to be obsolete in another 10 years as was the stereo receiver of 1992. The industry will slowly ramp up, stopping at 7.1 and 9.1 along the way towards the drive to make 10.2 the next defacto standard. Wife acceptance factor of our loudspeaker boxes will become an ever bigger issue as audiophiles move towards the 10 channel realization that if some is good, more is better.
