UTILIZATION OF THE ENERGY SPHERE IN MATRIX SURROUND RECORDINGS

• RM produces straight-line stylus motions. This is Scheiber's matrix. Sansui QS uses this too.
• The green, cyan, violet, and red lines have the same places (panned images between speakers).
• Scheiber put the four corner channels equally spaced between them:
  • Blue = LB (left back)
  • Dark green is LF
  • Yellow is RF
  • Magenta is RB
• Many 4-corner listeners notice "cogging" - smoothly panning heard as a jump from one
  side speaker to another on that side. Binaural hearing is limited with level-based-panning.

  Dolby Surround and the Hafler Diamond don't do this.

Front-oriented matrix systems

• Electro-Voice and Dynaquad have wide front angles and narrow back angles (top inset).
• Notice that almost all of the RM systems use only locations on the equator of the energy sphere. These are the straight-line stylus vibrations (ignore the black and brown dots).
• The locus of all of these straight-line vibrations is shown as the blue line on the usage sphere (which shows all parts of the energy sphere the matrix uses).

• Most RM systems use only the equator of the sphere (nothing else). So the rest of the sphere is unused.

Some matrix systems have a plane of sound instead of a ring of sound (middle inset).

• The QS and Dolby Surround matrix systems phase shift the back channels to avoid an encoding phase reversal. This makes the black clockwise circular motion when all channels get the same signal.
• These use up half of the energy sphere, because all locations anywhere inside the square of speakers are separate locations.
• The entire hemispherical shaded locus on the sphere is used here.

Add the author's matrix that makes a complete sphere of sound in the room (bottom inset).

• The Spheround matrix system uses circular motions in both directions to encode vertical placement of sounds.
• The black (clockwise) motion is the nadir (down) direction.
• The brown (anticlockwise) motion is the zenith (up) direction.
• This choice of directions was made so the QS centered sounds were down near the listener and not up in the air.
• All nadir and zenith locations use up the entire energy sphere (shaded usage).
• A room diagram for Spheround is shown to the far right. It is the same as the energy sphere, except that up and down on the sphere are traded for the QS reason (above).
• The page author is developing this. The decoder needs no new exotic equipment. And it cannot be patented because all patents covering its operation already existed (most by Peter Scheiber) and have now expired. It is in the public domain.
• the page author does not expect this to become anything big, but it has two advantages:

   It's fun to try (especially with an SQ record).

   It's easy to do, and even to encode. No computer necessary.

Phase Matrix systems: The Columbia SQ matrix and variants

SQ is based on using linear motion front channels and circular motion back channels:

• SQ grew out of a directive from Columbia executives that any Columbia matrix must have full separation between the front channels in stereo and quadraphonic play.
• This meant that Columbia could not use existing matrix systems (The Hafler Diamond does fit).
• SQ produces stylus vibrations that are straight lines, circles, and ellipses.
• Notice the motions go different ways than the Regular Matrix ones go.
• SQ uses all 6 primary orthogonal points and most of the sphere, so no space for vertical pans.

SQ Four Corners

• The SQ 4-corners encoder (top inset) gives an encoding for the sides different than the SQ position encoder gives (top of page).
• The 4-corners encoder was used mainly to encode discrete tapes into the SQ matrix.
• All phase matrix systems use most of the energy sphere with various stylus motions. Useless space is in between.
• The locus of these vibrations is shown as the blue lines on the usage sphere.

Variant versions of SQ are UQ, SQ 10-40 Blend, and EV Universal (middle inset).

• All have similar stylus motions (UQ shown).
• These use most of the energy sphere, using places near all 6 primary orthogonal points.
• Most of the hemispherical shaded locus is used, and also the front part of the equator.
• The UQ matrix corner channels (dark green, blue, magenta, and yellow) make a regular tetrahedron on the sphere. Separation between ANY two channels is 4.77 dB.

The page author tried to make a 3-D SQ matrix sphere of sound (bottom inset). It isn't very good.

• The SQueround matrix tries to put vertical sound into the SQ matrix or its variants.
• The vertical sounds use the diagonal splits.
• The brown (anticlockwise) elliptical motion is the zenith (up) direction. This matches the QS choices made above.
• All front locations are lateral, so this doesn't use up the entire energy sphere.
• Separations are unequal because vertical channels are closer to some than to others.

   Zenith is much closer to RF and LB channels.

   Nadir is much closer to LF and RB channels.

• Most of the hemispherical shaded locus on the sphere is used, as are the front laterals.
• A room location diagram for SQueround was impossible to generate. I used the one for regular matrix.
• This can be played with (if you can derive the signals).

In the page author's opinion, the SQ matrix wastes more of the energy sphere without any real gain from doing so,

Why were there so many different systems?

Each company wanted to own patent rights to the quadraphonic system that would be the standard.

No company wanted to pay patent royalties to any other company. This helped end quad.

Peter Scheiber's patent was broad enough to cover all matrix systems. No standard and royalty fights ended quad.

This problem didn't happen with stereo because Blumlein's patents expired before stereo was popular.

Uniform Matrix systems: Denon's UMX, BBC Matrix H, and UHJ Ambisonic

The UMX system is based on using linear motions for left and right channels and circular motions for front and back channels:

• This produces stylus vibrations that are straight lines, circles, and ellipses.
• The stylus motions go different ways than the Regular Matrix and SQ ones go.
• UMX motions are on a vertical great circle of the energy sphere, instead of the RM equator
   (UMX usage sphere - far right, bottom diagram).
• UMX was made to prevent the disappearance of back information in mono play.
   (It was also done to try to get around patents on RM and SQ).
• Phases cause normal stereo play of the UMX encoded recording to make front sounds (clockwise, left channel leading right) shift left, and back sounds (anticlockwise, right channel leading left) shift right. This is called "phasiness". Decoding removes this phasiness.

BBC Matrix H

• BBC's Matrix H was devised to get rid of the mono play disappearance of back signals without as much of phasiness problem in stereo play (above).
• This matrix system uses a great circle that is placed halfway between the QS equatorial plane and the UMX vertical plane. It is at a 45 degree angle (see usage).
• The locus of all of these vibrations is shown as the blue lines on the usage sphere.
• Matrix H can halfway (with lower front-to-back separation) play RM/QS and also UMX recordings. Matrix H recordings play halfway on RM, QS, or UMX players.

UHJ Ambisonic

• This is a further reduction of the phasiness of stereo playback without sacrificing mono play of back sounds.
• The phasings of this system tend to reduce the cogging problem.
• The locus of this system is not a great circle, but is concentrated on one side of the energy sphere.

The page author designed a UMX matrix that makes a complete sphere of sound in the room as a thought experiment (bottom inset).

• SpherUMX is like Spheround, but rotated on the energy sphere to match UMX.
• The (unused) lateral stylus motions (mono) sounds become the nadir (down) direction.
• The (unused) vertical stylus motions are the zenith (up) direction.
• This choice of directions was made to match the choices made above.
• This also has the phasiness in stereo play (above)
• No attempt has been made to use this idea. But it could work if the phasiness is ignored.
• These motions together use up the entire energy sphere.
• A room location diagram is the same (except for stylus motions) as Spheround.
• This can also be played with (the signals are much easier to get).

The page author notes that these uniform matrix variants suffer from phasiness in the stereo image when not decoded.

 

Now that all of the patents have expired, we might get to enjoy some quadraphonics again.