BUILDING MATRIX SURROUND SOUND ENCODERS

FOR AN ORDINARY STEREO MIXER WITH 4 TO 10 SUBGROUPS

UniQuad Read the parent article to learn how to choose a mixer, and how to use the encoders.

Why two SQ decoders can function as an SQ encoder:

How two SQ decoders can function as an SQ encoder:

What you need, in addition to the mixer

What you might need, depending on your equipment and intent:

Connectors that fit your equipment.
Balanced line mic cable.
Patch cords that fit your mixer.
Audio isolation transformers: 600 ohm to 600 ohm
Resistors of various values
Potentiometers
Heat shrinkable tubing that will fit over the resistors before shrinking
Small plastic utility box
Several terminal strips or a grid PC board
Strain reliefs or grommets
Drill and bits
Other wire
Soldering equipment and ability
Knowledge of balanced line connections
Digital delay unit capable of delaying by 15 milliseconds (for acroperiphony).

EQUIPMENT NEEDED FOR EACH ENTIRE ENCODING SYSTEM

Instructions (continued):

Find Out What Equipment is Needed for n Sources.
4−C = 4−Corner, DGS = Diagonal Split, F−O = Forward−Oriented, B−O = Backward−Oriented.

ENCODING SYSTEM EQUIPMENT REQUIREMENTS
ENCODING SYSTEM	EQUIPMENT NEEDED
ENCODING SYSTEM	Bus Swap Switch	Phase Inverter	Phase Switch	SQ Decoders	Advanced Phase Switch	RM/SQ Mode Switch	RM Acro Aux Send	Digital Delay	Mix Buses Need	Cross Faders For n	Chan Strips For n
RM (Dolby Surround) Basic	−	1	−	−	−	−	−	−	4	−	n
RM with Acroperiphonic Delay	−	1	−	−	−	−	1	1	4	−	n
RM & Single SQ	−	1	−	1	−	−	−	−	6	− †	n †
Single SQ, no RM	−	−	−	1	−	−	−	−	4	− †	1 †
RM & Double SQ 4−C	−	1	−	2	−	−	−	−	8	n	2n
RM & Double SQ 4−C, DGS	−	1	1	2	−	−	−	−	8	n	2n
RM & Double SQ 4−C, F−O	−	1	−	2	1	−	−	−	8	n	2n
RM & Double SQ 4−C, DGS, F−O, B−O	−	1	1	2	1	−	−	−	8	n	2n
Double SQ 4−C, DGS, F−O, B−O, no RM	−	−	1	2	1	−	−	−	4	n	2n
Switched RM or Double SQ 4−C	−	1	−	2	−	2−pos	−	−	4	−	n
Switched RM or Double SQ 4−C, DGS, F−O, B−O	−	−	1 ††	2	1	2−pos	−	−	4	n	2n
k Ultimate Encoder Pairs	−	−	k	k	k	k 3−pos	−	−	2k	n	2n
k Ultimate Encoder Pairs & RM Acroperiphonic	−	−	k	k	k	k 3−pos	1	1	2k	n	2n
k Ultimate Encoder Pairs & Back Sub Swap	k	−	k	k	k	k 3−pos	−	−	2k	n	2n

n is the number of sound sources used.

k is the number of encoding pairs used.

A Phlazex unit can be used as either a phase inverter or a phase switch.

† Need a cross fader and two channel strips for acroperiphonic panning.

†† The phase switch works for both (set to reverse for RM).

Variations:

If the subgroup buses have no inserts:
- Choose one stereo input for each bus pair in the chosen plan except RM FRONT.
- It may be a stereo AUX RETURN, a stereo channel strip, or a pair of panable mono inputs.
- Name them RM BACK RETURN, SQ FRONT RETURN, and/or SQ BACK RETURN as used.
- Do NOT assign the subs themselves to the main output. Assign the returns chosen instead.
If the subgroups have inserts, Name them RM BACK INSERT, SQ FRONT INSERT, and/or SQ BACK INSERT as used.
To add the RM Acroperiphonic capability:
- Select an after-fader AUX SEND (or EFFECTS OUT). Label it AP SEND.
- Also select a mono panable input channel or mono-capable AUX RETURN.
  For the Special Mackies, this input must be assignable to subgroups.
  Label it AP RETURN. The digital delay will be connected to the send and return
Note: If you chose channel inputs for any of the returns, setting the return level uses the channel fader plus any trim controls available. Assign the channel strips to RM FRONT.
Note: If you chose channel inputs for any of the returns, you can use a second small stereo mixer to mix all of the sub returns together, and use a single channel strip to return them. Assign the single strip to RM FRONT.

CONSTRUCTING THE CABLES

Note that if several switched or controlled devices are needed, they could be combined on a common control panel.

RM / DS Encoder

Patch cord A. Choose the selection that best fits your mixer:

You have built a UniQuad Phlazex. Uses standard patch cords. Set it for Encode Surround Right-Biased.
ENCODER INSERT jacks
Fully balanced SUB OUT and ENCODER RETURN jacks
Impedance balanced SUB OUT, fully balanced ENCODER RETURN
Unbalanced SUB OUT, fully balanced ENCODER RETURN
Unbalanced ENCODER RETURN
You had hum problems using one of the balanced methods.

The sample illustrations in the links show 1/4 inch phone plugs. Substitute the type of connector you are really using.

Acroperiphonic (AP) Encoder

Patch cord B. Find your AP RETURN type:

Patch cord C. Find your AP AUX SEND type:

Basic 4−Corners SQ Encoder

All of the patchcords are standard patchcords, or insert patchcords that fit the inserts and the SQ decoder. Use the diagram on the right above:

The 4−Corners encoder is the only SQ encoder that does not need the crossfaders or two channel strips per source.

Basic 4−Corners and Diagonal−Split−Oriented SQ Encoder

All but one of the patchcords are standard patchcords, or insert patchcords that fit the inserts and the SQ decoder.

The basic phase switch is the one special cord:

Build a custom phase reversing switch. Place it in the line for encoding the left back.
You have built a UniQuad Phlazex. Uses standard patch cords. Connect to both lines for encoding SQ back.
- For the normal phase position (4−corner), set Phlazex for Stereo Pass−Through
- For the reverse phase position (forward−oriented), set Phlazex for Encode Surround Right-Biased
The basic phase switch does not give optimum encodings of the left and right sides. It gives the optimal diagonal splits.

Two channel strips and a crossfader are needed to encode the sides or the diagonal splits.

Advanced 4−Corners and Forward−Oriented SQ Encoder

The advanced phase switch is a special cord set:

Build the advanced phase reversing switch. Place it in the lines for encoding the left back and right back as labeled.
The advanced phase switch changes the following abilities:
- For the forward−oriented encoder (reverse phase position), the left and right side encodings are optimum.
- Diagonal splits are not optimum, but are usable.
- It can't be used for the RM part of the switched RM or SQ encoder. A separate phase inverter must be used.

The normal phase position selects the 4−corners encoder, and the reverse position selects the forward−oriented encoder.

Two channel strips and a crossfader are needed to encode the sides or the diagonal splits.

Combined 4−Corners, Diagonal Split, Forward−oriented, and Backward−Oriented SQ Encoder

The basic phase switch (1) is the one special cord. The advanced phase switch (2) is a special cord set. Both are needed:

Build the custom phase reversing switch. Place it in the line for encoding the left back.
Build the advanced phase reversing switch. Place it in the lines for encoding the left back and right back as labeled.
The advanced phase switch changes the following abilities:
- For the forward−oriented encoder (reverse phase position), the left and right side encodings are optimum. Diagonal splits are not.
- It can't be used for the RM part of the switched RM or SQ encoder. A separate phase inverter must be used.
- Combined with the basic phase switch, it can produce the Backward−Oriented Encoder, if the second basic phase switch is inserted in the front left feed line.

Two channel strips and a crossfader are needed to encode the sides or the diagonal splits.

See the general switch table below to operate.

The Ultimate Encoder Pair or the switched RM / SQ Encoder

The basic phase switch (1) is a special cord. The advanced phase switch (2) is a special cord set. Both are needed, along with a stereo source selector. A swap switch can be added for CircleSurround:

Build the custom phase reversing switch. Place it in the line for encoding the left feed.
Build the advanced phase reversing switch. Place it in the lines for encoding the left back and right back as labeled.
The advanced phase switch changes the following abilities:
- For the forward−oriented encoder (reverse phase position), the left and right side encodings are optimum. Diagonal splits are not.
- It can't be used for the RM part of the switched RM or SQ encoder. A separate phase inverter must be used.
The source selector selects what kind of encoding will be done by the bus pair.
The swap switch is used to encode CircleSurround instead of SQ.

Two channel strips and a crossfader are needed to encode the sides or the diagonal splits.

See the general switch table below to operate.

CONNECTING THE CABLES TO THE MIXER

RM / DS Encoder

Install the RM encoder cable (patch cord A) when not using ENCODER INSERTS:
1. Plug patch cord A's LEFT SUB OUT connector into your left SUB OUT connector on the mixer.
2. Plug the RIGHT SUB OUT connector into your right SUB OUT.
3. Plug the LEFT ENCODER RETURN connector into the left ENCODER RETURN (with a pair of mono inputs, use the lower channel number).
4. Plug the RIGHT ENCODER RETURN connector into the right ENCODER RETURN (with a pair of mono inputs, use the higher channel number).
Install the RM encoder cable (patch cord A) with single-signal ENCODER INSERTS:
1. Plug patch cord A's LEFT ENCODER SEND connector into your left SUB INSERT SEND connector on the mixer.
2. Plug the RIGHT ENCODER SEND connector into your right SUB INSERT SEND.
3. Plug the LEFT ENCODER RETURN connector into the left SUB RETURN.
4. Plug the RIGHT ENCODER RETURN connector into the right SUB RETURN.
Install the RM encoder cable (patch cord A) with tip-ring-sleeve ENCODER INSERTS:
1. Plug patch cord A's LEFT ENCODER INSERT connector into your left SUB INSERT connector on the mixer.
2. Plug the RIGHT ENCODER INSERT connector into your right SUB INSERT.
When connecting a Phlazex, connect patch cables from it to the appropriate connectors on the mixer. If using TRS inserts, you will need standard insert cables.

Acroperiphonic Encoder

To install the acroperiphonic function, make the following connections:

Connect the mixer end(s) of patch cord B above to your AP RETURN.
Connect the delay end(s) of the patch cord B to the OUTPUT on the digital delay.
Connect the mixer end(s) of patch cord C to your AUX SEND.
Connect the delay end(s) of patch cord C to the INPUT on the digital delay.

Basic SQ BACK Encoders

The SQ decoders used should NOT have logic.

Notice that the back connections to the SQ decoder are crossed. This is what turns the back channels of the decoder into an encoder.

To install the basic SQ BACK 4−corner encoding function, make the following connections:

Connect the odd (left) submaster bus insert send to the right SQ decoder input.
Connect the right back SQ decoder output to the odd (left) submaster bus insert return.
Connect the even (right) submaster bus output to the left SQ decoder input.
Connect the left back SQ decoder output to the even (right) submaster bus insert return.
If such an ability is provided, disable the 10−40 blend of the decoder.

To install the basic SQ BACK 4−corner and forward−oriented encoding function, make the following connections:

Connect the odd (left) submaster bus insert send to the basic phase switch input or the left Phlazex input, using a suitable cable.
Connect the basic phase switch output or the left Phlazex output to the right SQ decoder input.
Connect the right back SQ decoder output to the odd (left) submaster bus insert return.
Connect the even (right) submaster bus output to the left SQ decoder input. If a Phlazex is used, insert the Phlazex right side into this cable.
Connect the left back SQ decoder output to the even (right) submaster bus insert return.
If such an ability is provided, disable the 10−40 blend of the decoder.

Advanced SQ BACK Encoders

The SQ decoders used should NOT have logic.

Notice that the back connections to the SQ decoder are crossed. This is what turns the back channels of the decoder into an encoder.

To install the advanced SQ BACK 4−corner and forward−oriented encoding function, make the following connections:

Connect the odd (left) submaster bus insert send to the right SQ decoder input.
Connect the left back SQ decoder output to the odd (left) advanced phase switch input.
Connect the odd (left) advanced phase switch output to the odd (left) submaster bus insert return.
Connect the even (right) submaster bus output to the left SQ decoder input.
Connect the right back SQ decoder output to the even (right) advanced phase switch input.
Connect the even (right) advanced phase switch output to the even (right) submaster bus insert return.
If such an ability is provided, disable the 10−40 blend of the decoder.

To install the combined SQ BACK 4−corner and forward−oriented encoding function, make the following connections:

Connect the odd (left) submaster bus insert send to the phase switch input or the left Phlazex input, using a suitable cable.
Connect the phase switch output or the left Phlazex output to the right SQ decoder input.
Connect the left back SQ decoder output to the odd (left) advanced phase switch input.
Connect the odd (left) advanced phase switch output to the odd (left) submaster bus insert return.
Connect the even (right) submaster bus output to the left SQ decoder input. If a Phlazex is used, insert the Phlazex right side into this cable.
Connect the right back SQ decoder output to the even (right) advanced phase switch input.
Connect the even (right) advanced phase switch output to the even (right) submaster bus insert return.
If such an ability is provided, disable the 10−40 blend of the decoder.

SQ FRONT Encoder

Notice that the front connections to the second SQ decoder are not crossed. The front channels do not interact.

To install the SQ FRONT encoding function, make the following connections:

Connect the odd (left) submaster bus insert send to the left input of the second SQ decoder.
Connect the left front SQ decoder output to the odd (left) submaster bus insert return.
Connect the even (right) submaster bus insert send to the right input of the second SQ decoder.
Connect the right front SQ decoder output to the even (right) submaster bus insert return.
If such an ability is provided, disable the 10−40 blend of the decoder.
An optional phase inverter switch can be added to the left channel to provide for SQ backward−oriented encoding.

SQ Bypass Switches

The SQ bypass switches are the RM−SQ switches in the diagram at right.

The SQ Bypass Switches can be:

Specially wired up switches
Internal bypass switches in the decoders.
Signal splitter and an off the shelf selector switch

The following table can be used for any of the SQ setups above.

If a switch is not included in your setup, its setting must be normal or SQ.

Setting the switches:

BYPASS SWITCH TABLE
OPERATION	FRONT BYPASS SWITCH	BACK BYPASS SWITCH	PHASE SWITCH 1	PHASE SWITCH 2	PHASE SWITCH 3
RM Encoder	RM	RM	Reverse	−	Normal
Stereo	RM	RM	Normal	−	Normal
SQ 4−Corners Encoder	SQ	SQ	Normal	Normal	Normal
SQ Diagonal−Split Encoder	SQ	SQ	Reverse	Normal	Normal
SQ Forward−Oriented Encoder	SQ	SQ	Normal	Reverse	Normal
SQ Backward−Oriented Encoder	SQ	SQ	Reverse	Reverse	Reverse
RM Acroperiphonic Encoder	SQ	RM	Reverse	−	Normal
RM Alternate Acroperiphonic ‡	SQ	RM	Normal	−	Reverse
SQ Acroperiphonic Encoder	RM	SQ	Normal	Normal	Normal

‡ The front input buses in the setting encode back channels, and the back input buses encode front channels.

Two channel strips and a crossfader are needed to encode the sides or the diagonal splits.

The Ultimate Encoder Pair with CircleSurround capability:

The Ultimate Encoder Pair with the CircleSurround swap switch. Do all of the following:

Trade the left and right decoder input lines (for the left back and right back signals).
Put the swap switch at the mixer bus outputs.
Add a switchable phase inverter (1) to the left source (going to the right input).
Add a switchable phase inverter and line swap (2) to the back outputs.
Trade the left front and right front output lines.
Add the RM−SQF−SQB switch (can use a stereo source selector switch) as shown.

All of the various switches for the Ultimate Encoder could be put in the same box and wired together (below).

Setting the switches - If a switch is not included in your setup, its setting must be normal or SQ:

GENERAL SWITCH TABLE
OPERATION	CHANNELS	SWAP SWITCH	PHASE SWITCH 1	PHASE SWITCH 2	MODE SWITCH	PAN POT CONTROLS	CROSS−FADE CONTROLS
Stereo Pass−Through	Stereo	Normal	Normal	−	RM	L − F − R	not used
Stereo Pass−Through	Phased	Normal	Normal	−	SQF	L − F − R	not used
RM Encoder	Front	Normal	Normal	−	RM	L − LF − F − RF − R	not used Use Flip Buses
RM Encoder	Back	Normal	Reverse	−	RM	L −LB − B − RB − R	not used Use Flip Buses
RM Acroperiphonic Encoder	Front	Normal	Normal	−	RM	L − LF − F − RF − R	F − C − B
RM Acroperiphonic Encoder	Back	Normal	Reverse	−	SQF	L − LB − B − RB − R	F − C − B
SQ 4−Corners Encoder	Front	Normal	Normal	−	SQF	LF − F − RF	not used Use Flip Buses
SQ 4−Corners Encoder	Back	Normal	Normal	Normal	SQB	LB − B − RB	not used Use Flip Buses
SQ Diagonal−Split Encoder	Front	Normal	Normal	−	SQF	LF − F − RF	F − Split − B
SQ Diagonal−Split Encoder	Back	Normal	Reverse	Normal	SQB	LB − F − RB	F − Split − B
SQ Forward−Oriented Encoder	Front	Normal	Normal	−	SQF	LF − F − RF	F − Side − B
SQ Forward−Oriented Encoder	Back	Normal	Normal	Reverse	SQB	LB − F − RB	F − Side − B
SQ Backward−Oriented Encoder	Front	Normal	Reverse	−	SQF	LF − B − RF	F − Side − B
SQ Backward−Oriented Encoder	Back	Normal	Reverse	Reverse	SQB	LB − B − RB	F − Side − B
SQ Acroperiphonic Encoder	Front	Normal	Normal	−	RM	LF − F − RF	F − C − B
SQ Acroperiphonic Encoder	Back	Normal	Normal	Normal	SQB	LB − B − RB	F − C − B
OPERATION	CHANNELS	SWAP SWITCH	PHASE SWITCH 1	PHASE SWITCH 2	MODE SWITCH	PAN POT CONTROLS	CROSS−FADE CONTROLS
UMX Basic Encoder	Left−Right	Normal	Normal	−	SQF	L − C − R	[L−R] − C − [F−B]
UMX Basic Encoder	Front−Back	Normal	Normal	Reverse	SQB	F − C − B	[L−R] − C − [F−B]
RM 3D Front Encoder	Front	Normal	Normal	−	SQF	L − LF − F − RF − R	Horiz − Oblique − Vert
RM 3D Front Encoder	Down−Up	Normal	Normal	Reverse	SQB	N − NF − F − ZF − Z	Horiz − Oblique − Vert
RM 3D Back Encoder	Back	Normal	Reverse	−	SQF	L − LB − B − RB − R	Horiz − Oblique − Vert
RM 3D Back Encoder	Down−Up	Normal	Reverse	Reverse	SQB	N − NB − B − ZB − Z	Horiz − Oblique − Vert
CircleSurround Encoder	Front	Normal	Normal	−	SQF	LF − F − RF	F − Side − B
CircleSurround Encoder	Back	Swap	Normal	Reverse	SQB	LB − F − RB	F − Side − B

Two channel strips and a crossfader are needed to encode the sides or the diagonal splits.

Combining the Ultimate Encoder Pair controls on a control panel

The controls for several Ultimate Encoder Pairs can be built into a common control panel.

The switches are mounted left to right on the panel in the order they are listed in the table above.

Normal positions indicate that the switches on the panel are thrown to the left.

The controls are shown set as follows:

Subs 1 & 2: RM Fronts
Subs 3 & 4: RM Backs
Subs 5 & 6: SQ Forward−Oriented Fronts
Subs 7 & 8: SQ Backward−Oriented Backs

SWAP SWITCH − PHASE SWITCH 1 − PHASE SWITCH 2 − MODE SWITCH

Meanings of the abbreviations on the control panel:

4C − The back channels of the SQ 4−Corners Encoder
BO − The SQ Backward−Oriented Encoder − use for both front and back
CS − Encode CircleSurround back channels instead of SQ back channels
DG − The SQ Diagonal Split Encoder
FO − The SQ Forward−Oriented Encoder
FT − Use for all front encoding except SQ Backward−Oriented
RB − Encodes the back channels of RM
RM − The Regular Matrix system, including Dolby Surround
SQ − The CBS StereoQuad system
SQB − Encode back channels of SQ and CS
SQF − Encode front channels of SQ and CS

Output

Connect the destination (a tape recorder, CD recorder, or a surround sound decoder feeding a PA) of the encoded surround sound to the mixer MAIN L and R outputs. Also connect a surround sound decoder so you can monitor the results.

What happens if the SQ 10−40 blend can not be disabled?

The effects on the encoder if the SQ decoders still have their 10−40 blends:

SQ front encoding: The pan positions are slightly moved toward the center, but not enough to cause any trouble.
SQ back encoding with the phase switch in the Normal Position: The pan positions are spread out slightly. Moving the panpot inward a bit compensates. But center back encoding is also reduced in strength somewhat, requiring a higher fader setting.
SQ back encoding with the phase switch in the Reversed Position: The pan positions are moved forward from the optimal LB and RB positions.
It is usually easy to either remove the blend resistors or put them on switches so they can be disabled.
Phlazex units can be used to completely compensate for the blend resistors. One is needed for the front, and another for the back Connect them immediately after the decoders.

LINKS: