Maxtrix & Discrete
Once the soundtrack is complete, it’s up to your player and receiver to output the sound to the proper speakers. There’s two terms to keep in mind here: matrix and discrete. We’re not talking about a secret Keanu Reeves movie; we’re talking about how the sound field is reproduced to your speakers.

In a discrete recording, each channel is given its own separate audio to reproduce. So in a 5.1 channel discrete recording, all five channels have a different audio stream to play. Both Dolby Digital and DTS Digital Surround offer 5.1 channels of discrete audio.

In a matrix soundtrack, the same audio is sent to certain channels and then split on playback. This usually occurs in the rear channels. If a soundtrack is mixed in 5.1 and played back on a 7.1 setup, the receiver is using matrix technology to reproduce five channels as seven.

Home Setup
When setting up your home entertainment system, several factors come into play when deciding on how many speakers to use. Kale Lohmann, a CEDIA-certified professional with Paragon Sight and Sound in Ann Arbor, Mich., says he looks at things like the number of seats as well as room size when determining optimum speaker setup.

“We want to make sure we fill all the gaps in a room,” Lohmann said. “The more rows of seats or the longer a room is, the more likely we are to use a 7.1 setup to ensure that there’s no loss in the sound stage.”

In smaller, more square rooms, a 5.1 channel system might be more than adequate, Lohmann said. And while too many speakers may be overkill in a room, he doesn’t believe it reduces quality.

The most common setups now are 5.1 and 7.1. The inherent problem with a 6.1 speaker setup is that when there’s more than one seat in a room, a rear center channel is not the best option to disperse sound evenly to all listeners. And since DTS ES is the only technology that can reproduce a 6.1 soundtrack discretely, the majority of discs are authored in either 5.1 or 7.1, so there’s not as much content designed specifically to take advantage of the 6.1 setup.

The consumer trend certainly seems to be toward more speakers. “We’re doing mostly 7.1 installs now unless it’s a small room, or a multipurpose room like a family room,” Lohmann said. And now that Blu-ray is starting to gain momentum and next-generation receivers and players are plentiful, that momentum shows no signs of slowing.

In the end, the goal is an amazing-sounding system. Your budget and a consultation with a professional can help you determine the best way to outfit your room. All 7.1 sound-tracks are backward compatible to 5.1, so while you might miss out on a more expansive sound field, having a 5.1 system is certainly not a handicap.

Trust me, nearly 20 years later, Top Gun still sounds great on a 5.1 or a 7.1 system.

Suggested Reading:
- How to Calibrate a 5.1 Sound System for Movies
- Great Movie Scenes for Surround Sound
- The Book on Bookshelf Speakers

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