WHY DO WE WANT QUADRAPHONIC OR SURROUND?

DIFFERENT PEOPLE HAVE DIFFERENT REASONS WHY THEY WANT MORE THAN STEREO

Different reasons why people want surround sound or quadraphonics:

1. Concert-hall realism
2. Movie-theater realism
3. Rock concert realism
4. Live surround music
5. Live music recording
6. Television broadcasts
7. Surrounded by musicians
8. Sound effects
9. Producing albums in surround
10. The "you are there" realism
11. Surround from stereo records
12. Sound-in-the-round
13. Sound-in-a-sphere
14. Sounds of nature
15. Conserving historic recordings
16. Electronic gadgetry
17. Advertising

Here is a list of the claimed ideals in surround sound or quadraphonics

1. A continuous surround field (the "You are there" effect)
2. Preventing aural location of the speakers
3. Ability to pan a sound source anywhere in the room
4. Ability to pan sound sources smoothly
5. Ability to place a sound source anywhere in the listening room
6. Recording ambient sounds
7. Discreteness
8. Removing the side localization problem
9. Removing the head turning problem
10. Preventing crosstalk
11. Preventing pumping artifacts
12. Preventing clustering of sounds at the speakers
13. Maximum compatibility with existing equipment and media

The different methods that are in use:

How are each of these best achieved?

QUADRAPHONICS AND SURROUND:
WHAT DO WE REALLY WANT?

QUADRAPHONICS QUANDARY

Here is a list of frequently asked questions about the Quadraphonic Quandary:

1. What is a continuous surround field

   This is a field created by the speakers that makes you think that you are really at the place where the recording was made.

   Binaural sound is an example of a sound field when listened to through headphones.

   The ideal surround sound field works with either headphones or speakers.

2. What is prevention of aural localization of the speakers?

   This is the desired case where the listener can't find the speakers by listening for them.

3. What is the ability to pan sound sources smoothly?

   This is the ability to turn a pan pot to pan a source and have the image of the source move smoothly around the listener without any sudden jumps or dead spots where the image does not move.

4. What is recording ambient sound?

   This is using an array of microphones to preserve the sounds that exist in the environment and the directions they come from.

5. What is a discrete surround sound system?

   This is a system with a separate sound channel for recording each sound source or microphone.

6. What is discreteness?

   This is the amount of separation between the separate recording channels in the medium.

7. What is matrix?

   This is a system where a number of sound sources greater than the number of recording channels in the medium are encoded into the smaller number of channels in a way to preserve the direction each sound comes from.

8. What is the side localization problem?

   This is where a listener facing forward cannot locate a sound panned between two speakers on the same side of the listener. This is a known problem with quadraphonic and surround sound. The listener has to turn his head to correctly hear the side image.

9. What is the head turning problem?

   This is where a good sound image created by a surround system falls apart when the head of the listener is turned.

10. What is removing crosstalk?

    This is the use of a separation enhancement system to remove the effects of matrixing to increase the separation between channels.

    Two methods were used:

    1. Automatic gain riding/compression
    2. Automatic decode matrix varying
11. What are pumping artifacts?

    These are the unintentionally audible effects of a separation enhancement system as it works to increase the separation between channels.

12. What is clustering of sounds at the speakers?

    This is an effect of the human hearing system when it finds the locations of the speakers instead of the sound sources where they are intended to be.

    Hugh Robjohns in his article "Surround Sound Explained" called this "puddles of sound at the speakers".

13. What is maximum compatibility with existing equipment and media?

    This is making unnecessary a large amount of new equipment and a variety of new media formats that are incompatible with normal stereo media that are commonly available.

REMEDIES

1. How can a continuous surround field be created?

   There are several methods:

   1. Use binaural spaced mic techniques (requires headphones)
   2. Use multiaural spaced mic techniques (e.g. surrfield and spheround)
   3. Use multiaural sound delay techniques
   4. Use overall sound delay techniques (e.g. Dolby Surround)
2. How can aural localization of the speakers be prevented?

   Reduce the discreteness of the recording.

   Use a matrix system.

   Use level panning in all directions.

   Use delayed sounds in speakers on the opposite side of the room.

   Use Dolby Surround (1977), Dolby Pro-Logic, or Dolby Pro-Logic II.

3. How can sound sources be panned smoothly?

   Use level panning in all directions.

   Also use delayed sounds in speakers on the opposite side of the room.

4. How is ambient sound recorded?

   There are several good methods:

   1. Use binaural-spaced mic techniques
   2. Use multiaural-spaced mic techniques (surrfield and spheround)
   3. Use multiple mics spaced far apart, each to a separate recording channels
5. How is a discrete surround sound ideally recorded?

   There are several good methods:

   1. Use multiaural-spaced mic techniques.
   2. Use multiple mics spaced far apart, each to a separate multitrack recording track. Then use one of the techniques below.
   3. Mix down to a discrete 4-channel mix.
   4. Use studio recording techniques to record individual tracks to a multitrack, then mix down using a mixer with one bus for each channel
   5. Use a 4-bus mixer to simultaneously make a live mix (played through a discrete PA) and record a discrete recording.
6. How is discreteness maximized?

   Mixing so that any one sound source appears in at most two speakers.

7. How is matrix recorded?

   There are several good methods:

   1. Use multiaural-spaced mic techniques (surrfield and spheround).
   2. Use multiple mics spaced far apart, each to a separate multitrack recording track. Then use one of the techniques below.
   3. Use studio recording techniques to record individual tracks to a multitrack. Then use one of the techniques below.
   4. Use studio recording techniques to record to a multitrack, then mix down to a discrete 4-channel mix, and then encode with a 4-corners encoder.
   5. Use studio recording techniques to record to a multitrack, then mix down using an encoding mixer (method here).
   6. Use an encoding mixer to simultaneously make a live mix (played through a matrix decoder) and record a matrix recording.
8. How is the side localization problem removed?

   There are several methods:

   1. Use binaural-spaced mic techniques
   2. Use multiaural-spaced mic techniques (surrfield and spheround)
   3. Use delayed sounds in speakers on the opposite side of the room.
   4. Use Dolby Surround (1977), Dolby Pro-Logic, or Dolby Pro-Logic II.
9. How is the head turning problem removed?

   Multiaural spaced mic techniques work.

   These methods combine to work:

   1. Use level panning in all directions.
   2. Use delayed sounds in speakers on the opposite side of the room.

   Use Dolby Surround (1977), Dolby Pro-Logic, or Dolby Pro-Logic II.

10. What is removing crosstalk?

    This is the use of a separation enhancement system to remove the effects of matrixing to increase the separation between channels.

    Three methods were used:

    1. Automatic gain riding or compression/expansion
    2. Automatic decode matrix varying
    3. Multiaural spaced mic techniques remove the need to remove crosstalk by steering it.
11. How are pumping artifacts prevented?
    1. Do not use automatic gain riding or compression/expansion
    2. Carefully time the automatic decode matrix varying
    3. Use less of the automatic decode matrix varying
    4. Multiaural spaced mic techniques do not pump.
12. How can clustering of sounds at the speakers be eliminated?

    Prevent aural localization of the speakers.

    Use level panning in all directions.

    Use delayed sounds in speakers on the opposite side of the room.

    Use Dolby Surround (1977), Dolby Pro-Logic, or Dolby Pro-Logic II.

13. How can maximum compatibility with existing equipment and media be achieved?

    Do not use esoteric or little used technologies or recording formats.

    Use well-known technologies, such as the LP, cassette, CD, and .wav files. These can be played on equipment that most people have or can easily get.

FACTIONS

There seem to be a set of factions with different goals in the reproduction of surround sound. Sometimes their goals are at odds with each other. This will examine the various goals and what must be done to satisfy them.

1. What factions of surround sound exist?

   Here is a list of the various factions.

   • FIELDISTS - Those who want a continuous surround field
   • FREEPANNERS - Those who want maximum freedom to place sound sources in the room
   • DISCRETISTS - Those who want maximum discreteness
   • ANARTIFERS - Those who want no side localization, head turning, and pumping artifacts
   • COMPATIBLERS - Those who want maximum compatibility with existing media.
2. What are the opinions of the members of these factions about these items?

   Here is a table of the various opinions:

   ITEM	FIELDISTS	FREEPANNERS	COMPATIBLERS	ANARTIFERS	DISCRETISTS
   Max compatibility	What we want	What we want	What we want	What we want	Not wanted
   Continuous surround field	What we want	Desirable	Doable	This is good	Too smeared
   Fix clustering	What we want	What we want	What we want	If no artifacts	Not wanted
   Fix pumping	What we want	What we want	Doable	If no artifacts	Can't be done
   Fix side localization	What we want	Doable	Doable	If no artifacts	Ruins discrete
   Fix head turning	What we want	What we want	Doable	If no artifacts	Doable
   Matrix is better	What we want	Doable	What we want	Doable	Not wanted
   Prevent speaker location	What we want	This is good	Doable	If no artifacts	Ruins discrete
   Pan anywhere	This is good	What we want	Doable	If no artifacts	Doable
   Smooth pan	This is good	What we want	Doable	Doable	Doable
   Record ambience	What we want	Doable	Doable	Doable	Doable
   Remove crosstalk	Doable	Doable	Doable	If no artifacts	Unnecessary
   Discrete is necessary	Not wanted	Doable	Not wanted	Desirable	What we want
   Special recording formats	Not wanted	Doable	Not wanted	Doable	What we want

Notice the resulting patterns.