Surround and Stereo sound doesn’t work everywhere

Marketing has taught consumers to expect surround sound and theatre quality no matter where they are. From a technical standpoint, this is not something that we can achieve in every space.
In order to describe this let’s forget about technology for second. The way your two ears hear sounds allows your brain to determine where they came from.

Imagine for a minute you are sitting in the front row of the concert hall. There’s an orchestra playing directly in front of you on the stage. Let’s assume that this is a full-scale orchestra there are 90 different musicians all playing their own instruments. Typically they would be arranged into four sections; strings, woodwinds, brass, and percussion (from front to back respectively). Because of the spatial separation of the musicians, all of the different sounds that you hear are not coming from the exact same place. Recording an orchestra in stereo works much the same way as someone sitting there listening. You would actually have one microphone pointed towards the left and one microphone pointed towards the right. (note that there are actually varying techniques for this). When played back in stereo, the sound would come from two speakers and re-create a very similar experience to sitting right in front of the orchestra.

The reason for this long winded example was to explain the basics of stereo sound and where it came from. You can think of surround sound as an extension to this. In addition to left and right, we have added more dimensions (Front to back). We will go more into depth on different surround configurations later, at this point we just wanted to illustrate that surround sound is really an extension of stereo sound.

Many of the spaces that we have to deal with in commercial systems rely on sound from ceiling speakers. People in the room may be seated in any configuration or direction. Because of an unpredictable orientation with respect to the speakers, these types of rooms simply do not allow for a proper stereo or surround audio experience. Going back to our example this would be a kin to say sitting in the auto facing the back of the room. You still hear the orchestra, but the clarity and distinction of the instruments would just not be the same.

Based on this logic, the only real way to get a stereo or surround sound experience is in a room is with fixed seating where the chairs cannot physically be moved in relation to the speakers. Picture a movie theater, where people all face in one direction and focus on the front of the room.

In reality there are some legitimate uses to having at least stereo sound in a space. Almost all recording music is processed in stereo. Even if you don’t have the perfect stereo experience the benefits from gaining a bit of separation from the left and right speakers can make a noticeable difference in audio quality. Unfortunately this only really works in smaller rooms and is definitely not perfect.

If you’re dealing with stereo sources (as most consumer devices are) when converting to Mono you want to make sure to use some sort of summing circuit for DSP and avoid the common mistakes of either just using the left channel, or jamming left and right channel together. When you connect the left and right channel together without using any sort of something circuit, you will experience some phase cancellations. These become very noticeable with MP3 and other compressed formats. You can also experience a loss of bass and the resulting audio becomes very thin and weak.

About the author

Dustin has been involved in the Professional Audio Visual industry for over 20 years, working for integrators both big and small. Learning the ropes through many years of trial, error, and firsthand experience, Dustin is passionate about creating resources to help share the knowledge that he has obtained the "hard" way.

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