What's wrong with two speaker stereo?
For the past 35+ years most everyone has listened to reproduced music via a two speaker stereo system. Stereo most commonly refers to a "two channel" system consisting of a left and right channel. Two channel stereo is a good system that can be incorporated into everything from personal "walkman" stereos all the way up to "high-end" home systems.

Two channel stereo provides a considerable improvement over one channel "mono" systems. Stereo provides "soundstage width" where various instruments can be heard across the plane of the two speakers which produced the left and right channel information. Stereo also provides more warmth to a recording by reproducing some of the ambiance of the hall or studio the performance was recorded in. However, when you are attending a concert, you (consciously or not) hear the hall ambiance as it is reflected from the surrounding walls of the hall itself. In a typical two speaker home stereo set up, much of this ambiance is "masked out" due to the fact that all the reproduced sounds are coming from your front speakers. The ambiance is "lost" amidst the direct sounds coming from the performance itself.

So what can surround sound do for me?
Surround sound, on the other hand, provides a way of "unmasking" the reverberent sounds of the recording space. By having two or more speakers to the rear of the listener, surround sound can "recreate" the ambiance of the original recording environment--whether it be a studio, club, concert hall, or other environment. 

As surround sound provides us with the recording's ambiance, the whole performance become more fuller, richer, sounding. There's a liveness "you are there" experience that is hard to describe. Often the soundstage takes on a 3 dimensional quality. Note though that the quality and quantity of the soundstage depth and ambiance will vary considerably from recording to recording.

Do all types of music benefit from surround sound?
Generally yes. However, by far and away, the best use of surround sound, in my opinion, is when reproducing concert hall recordings and live performances. Symphonic works recorded in a large hall especially benefit from the unmasking of the hall ambiance that surround sound provides. If you're a fan of classical music and have not yet given surround sound a try, please read on. Pop music that has been recorded as a series of individual tracks and then later mixed together, generally benefits the least from surround sound. Any music, pop or otherwise, that is recorded live, will benefit significantly from the additional realism you experience from a surround sound system.. Also some pop artists include special effects in their music which work especially well when played thru a system with surround sound.

Besides for unmasking the ambiance of a recording, does surround sound offer other improvements to the music?
Yes. In addition to unmasking the reverberent sound of the original recording space, surround music reproduction seems to significantly improve a systems dynamic range and tonality especially when played at low to moderate volume. What I'm trying to say is, when a stereo is played at a low "background music" level, the tonality of the reproduction is usually muted. When you turn on the surround sound speakers, however, the system sounds significantly louder during fortissimos and the instrumental timbres are much truer to life.

How does surround sound work?
We normally think of a 2 channel stereo recording as consisting of a separate left and right channel. But stereo can be processed in another fashion. Two channel stereo can also consist of a mono "sum" channel (which contains the sum of the left and right audio channels) along with a "difference" channel (which contains the imaging and ambiance information). Depending on how we superimpose this difference channel upon the sum channel, we can derive either the left or right channels of sound. The industry has developed designations for these channels. The mono "sum" channel is designated as the "L+R" (Left+Right) channel. The difference channel is designated as the "L-R" (Left-Right) channel.

Indeed, this is how FM stereo radio is broadcast while remaining compatible with older non-stereo FM receivers.. We have the mono sum (L+R) channel that non-stereo FM tuners can receive. Broadcast next to the L+R carrier is the difference channel (L-R) containing the imaging and ambiance information . An FM stereo receiver can process the sum (L+R) and difference (L-R) channels in such a way as to derive both a left and right channel of sound.

Surround sound encoded movies take advantage of this sum/difference channel relationship to deliver music and other audio effects to the rear speakers of your home or in the theater.

In addition to deriving the front left and right channels, a surround sound system takes this (L- R) difference channel and plays this channel thru the "rear" speakers. I say "rear speakers" since these speakers are often located behind the listener. However, they could also be located to the sides of the listening area. In any case, nearly all matrix surround sound systems use an additional pair of speakers located at or near the back of the listening environment.

Surround sound is especially good at unmasking the reflected sound from a recording. Reflected sound is the sound you hear from the wall reflections of any acoustic environment. (Contrast this with the direct sound you would hear from the stage and performers themselves.) Often you are not consciously aware of the reflected sound but it makes a huge difference in your perception of the sonic event. For example, a symphony orchestra playing out in an open field would sound far different from the same players in Carnegie Hall. Because of the nature of reflected sound, (much of it is out of phase from the direct sound), it ends up in the Left - Right difference channel of a stereo recording. Surround sound allows this ambient sound to be directed to you from behind (or from the sides of) your listening environment. Precisely as it would in "real life". Thru the use of rear speakers, the ambient sound is no longer masked out by the louder direct sound coming from your two front speakers.

Matrix surround advantages
Note, this web site page focuses on matrix surround and how it can be easily added to your existing stereo system(s). I'm a big fan of matrix surround for several reasons. Some of them being:

Realistic, natural ambiance
One of the big advantages of matrix surround sound systems is the realism of the sound reproduction. There is nothing artificial added to matrix surround. If the recording was done in a small space, the ambiance reproduced will be small. If the recording was done in a large concert hall that had considerable reverberations, then the surround sound speakers will reproduce that effect quite clearly. Of course, unlike the concert hall, at home you can adjust the surround speaker volume. This allows you to "dial in" the amount of reflective sound you desire. In a sense, you can move closer or further away from the performing stage, by controlling the amount of reflective sound you wish to hear.

No special source material needed.
Matrix surround systems do not need any special program material. Any good stereo recording most likely will sound better. Stereo and Dolby Surround movies will also sound great when played thru a low-cost matrix surround system. A simple do-it-yourself matrix surround system provides 80% of the effect that you would get with a more costly surround sound set up.

Of course you certainly can certainly play back material encoded in Dolby Surround, ambisonics, binaural, or other specially encoded source material thru a matrix surround system. Matrix surround works well with all these types of source material. In my own experience, however, I find that any good stereo recording, especially those made in a large concert hall will benefit significantly from matrix surround playback.

Inexpensive and relatively easy to implement
You don't have to buy a new receiver, additional amplifiers, or special processors to enjoy matrix surround. (You do need to be able to set up two additional speakers either to the sides or rear of your listening area.) You can add matrix surround without any internal modifications to your existing stereo system as you will see below.

What all surround systems require
Note, surround sound requires stereo playback. Non-stereo (mono) recordings or most AM radio tuners are single channel (monaural). Such sources contain no L-R channel information so the rear speakers will be totally silent when playing back non-stereo material. This is why you must also have a Hi-Fi stereo VCR if you wish to enjoy surround encoded VHS movies.

Okay, you've got my curiosity up. How can I add surround sound to my existing system?
Immediately below this paragraph is a link entitled "Do it yourself surround". Clicking on this link will take you to a page where you can review 3 different ways of adding matrix surround sound to an existing two channel stereo system. The beauty of this approach is that it does not involve any internal modifications to your existing equipment. (Though you do need to be careful as some amplifiers cannot handle the additional current load demanded by these circuits.) Upgrading your existing system to matrix surround, in the manner described on my "Do it yourself..." page is the most inexpensive way you can experience surround sound. 

I've got additional questions. May I email you?
It's been a few years since I've been actively involved with surround sound.  So I probably won't be a very good resource.  But feel free to email me if you do have an unanswered question regarding the material on this web site.   My name is Chris and I can be reached at: ckantack@yahoo.com

This web page was last updated on: 01/25/20 11:59 AM Pacific Time.