Why Surround is Better Than Stereo or Quadro

When you listen to surround sound you'll notice quite a few improvements over stereo:

• The sonic clarity is enhanced because the center channel anchors the sound and eliminates any phantom image shifts that we take for granted in stereo.

There is no sweet spot per se. — Actually, the whole room becomes a sweet spot in that you can move around freely and never loose the sense of clarity, dimension and spatial continuity. One listener described it perfectly as an "audio sculpture" in that, just like when you walk around a piece of artwork and get a different perspective of the art, when you walk around the 5.1 room you just get a different perspective of the mix. You might get closer to the guitar player, for instance, if you walk to the left of the room. Walk to the right and you're closer to the piano. Indeed, you don't have to even be in the speaker field to get a sense of the depth of the mix. While mixing, people sitting on a couch outside of the soundscape often describe an enhanced experience.

Speaker placement is very forgiving. — Yes, there are standards for placement, but these tend to be very non-critical. The sense of spaciousness remains the same regardless of how haphazardly the speakers are distributed around the room. In fact, stereo is far more critical placement-wise than surround sound.

SURROUND MIXING

During mixing, there are several surprising advantages:

Clarity of instruments — Everything sounds much more distinct as a result of having more places to sit space-wise in the mix. This means that you spend a lot less time EQing, trying to get each instrument heard.

Added dimension — Even mono tracks are big and dimensional in surround! No longer is there a need to "stereo-ize" a track by adding an effect. Simply spreading a mono source across the speakers with the pan pot makes it big sounding.

The ambience is different — When you mix in stereo, usually you must recreate depth. In surround, it's built-in. Because of the naturally increased clarity and dimension, you no longer have to spend as much time trying to artificially add space with reverb, delays, etc. This is not to say that you won't use these effects at all, but the approach is different, since surround automatically gives you the depth that you must artificially create with stereo.

Mixes go faster — it actually takes less time to do a mix because surround sound automatically has a depth of field that you normally have to work hard to create when you're mixing in stereo. Most mixers find they need less EQ and less effects because there's more room in the soundscape to place things.

Differences Between Surround for Picture and for Music

Normally in the theater, all of the primary sound information comes from the front speakers and the surround speakers are utilized only for ambience info in order to keep your attention on the screen. The LFE is intended to be used just for special effects like explosions and earthquakes and is therefore used infrequently. One of the reasons that the surround speakers don't contain more source information is a phenomena known as the "exit sign effect," which means that your attention is drawn away from the screen to the exit sign when the information from the surrounds is too loud.

But music-only surround sound has no screen on which to focus and therefore no exit sign effect to worry about. Take away the screen and it becomes possible to utilize the surround speakers for more creative purposes.

SURROUND MIXING SCHOOLS OF THOUGHT

Classical vs. "Middle of the Band"

There are two schools of thought about how surround sound for music should be mixed. The Classical method puts the music in the front speakers and the hall ambience in the surrounds, just as if you were sitting in the audience of a club or concert. This method may not utilize the LFE channel at all and is meant to reproduce an audience perspective of the musical experience.

In the case of the Middle of the Band method, the band is spread all over the room via the five main speakers (the LFE may be used for bass and kick, which is also spread to the other speakers as well) and that puts the listener in the center of the band and envelopes him with sound. This method usually results in a much more dramatic soundstage that is far bigger sounding than the stereo that we're used to. This may not be as authentic a soundscape as some music might require, however (for example, any kind of live music where the listener's perspective is from the audience).

WHAT DO I PUT IN THE CENTER CHANNEL?

In film mixing, the center channel is used primarily for dialogue so sonic movement doesn't distract the listener. In music, however, its use prompts debate among mixers.

No Center Channel

Many veteran engineers who have mixed in stereo all their lives have trouble breaking the stereo paradigm to make use of the center channel. These mixers continue to use a phantom center from the left and right front speakers and prefer to use the center speaker as a height channel or not use it at all.

Isolated Elements in the Center Channel

Many mixers prefer to use the center channel to isolate certain elements such as lead vocals, solos and bass. While this might work in some cases, many times the isolated elements seem disconnected from the rest of the soundscape (see Figure 14).

Figure 14 Isolated Elements in the Center Channel

Stereo VS Surround Stereo VS Surround 2

The Center as Part of the Whole

Mixers who use the center channel to its fullest find that it acts to anchor the sound and eliminates any drifting phantom images. In this case, all five speakers have equal importance with the balance changing the sound elements placed in the sound-scape. It's actually easiest to picture this as in Figure 15, with the soundscape cut in half from the middle of the center speaker.

Figure 15 Integrated Center Channel

Why Surround is Better Than Stereo

WHAT DO I SEND TO THE LFE (SUB-WOOFER) CHANNEL?

Anything that requires some low frequency bass extension can be put into the sub-woofer via the LFE channel. Many mixers put a little kick and/or bass there if it's used at all. Remember that the frequency response only goes up to 120Hz so you have to put the instrument into the main channels as well, in order to gain some definition.

In fact, it might be better not to use the LFE channel unless you're positive that the sub-woofer is calibrated correctly. An un-calibrated sub-woofer can cause big surprises in the low end when the track is later played back on the typical home theater setup. If you don't use the sub when mixing, the low frequencies under 80Hz are naturally folded into the playback sub-woofer resulting in a smooth and even response.

SURROUND TO STEREO COMPATIBILITY

Although it's possible to have the surround mix automatically down-mixed to stereo either via SMART Content down-mixing inherent in a DVD-Audio disc or by selection of the down-mix parameters on the Dolby Digital encoder, the results are often unpredictable and many times unsatisfactory. It's best to prepare a separate dedicated stereo mix whenever possible since their will most likely be sufficient room on the delivery medium (DVD).

SURROUND MASTER RECORDERS

Although any multitrack format can be used as a master recorder, the de facto standard is the Tascam DA-88 family (DA-98, PCM800, etc), sometimes enhanced to 20-bit resolution with either Rane or Prism bit splitters. Other machines being used include the Genex GX8000 and 8500 Magneto Optical recorders and Tascam MMR-8 hard disk recorder. Some people are even mixing to 1- or 2-inch 8-track analog.

MASTER TAPE TRACK ASSIGNMENTS

Sooner or later during one's first surround mix, the questions of channel assignment on the master recorder (be it tape or disc) always arise. What is the correct track assignment? Actually, there are several generally accepted channel assignment formats for surround, although the first is fast becoming the de facto standard. That is:

Channel 1 Channel 2 Channel 3 Channel 4 Channel 5 Channel 6

Left Front

Right Front

Center

LFE

Left Surround

Right Surround

DOLBY, SMPTE AND ITU STANDARD

A dedicated stereo mix, or Lt, Rt or encoded AC3 can be recorded onto Tracks 7 and 8. This format transfers easily to the corresponding four audio tracks (L, R, C, LFE) of the video formats widely used today such as DigiBeta or D5. This accommodates the necessary L, С and R tracks, as well as the common pairing of channels in Dolby Digital. The surround products of Panasonic, Mackie and Martinsound, to name just a few, now support this configuration. It is also the SMPTE and ITU standard.

The following two assignment methods are also used, but less and less as the above takes hold:

FILM STYLE

Channel 1 Channel 2 Channel 3 Channel 4 Channel 5 Channel 6
Left Front Center Right Front Left Surround Right Surround LFE

DTS

Channel 1 Channel 2 Channel 3 Channel 4 Channel 5 Channel 6
Left Front Right Front Left Surround Right Surround Center LFE

The above assignment is preferred by DTS. Again, the pairings are logical, but the placement is different from the Dolby standard. Tracks 7 and 8 usually contain the stereo version of the mix, if one is needed.