QUADRAPHONIC MIXING
FOR A STAGE PLAY IN 1971

Prologue: The query that led to the project:

A friend came to me in late 1970 with a technical question: Can five tape recorders be synchronized?

I began to think on the complexity of this question, including the following facts:

1. They wanted sound effects to come from at least 5 different directions in the auditorium.
2. They were talking about the Wollensak mono tape recorders that most schools had in the 1960s.
3. Those Wollensak tape recorders had no synchronization capabilities.
4. I had been experimenting with the Hafler (Dynaco) quadraphonic system earlier in the year.
5. Several ideas came to mind:

   - Use one tape recorder and switch among several speakers. This would require switch position cues for each sound.
   - Switching speakers also required as many speakers as the number of directions the sounds need to come from.
   - Turn on a separate tape recorder for each wanted sound direction.
   - Use a quadraphonic system and recording.

We decided to use the Hafler quadraphonic system using a stereo tape recorder, a stereo amplifier, four speakers, and lots of speaker wire.

The Auditorium we Used

This was a typical high-school auditorium except that it was designed with safety in mind.

• All levels are accessed by stairways, not ladders.
• A raised walkway goes around the entire outside of the stage and audience areas.
• The walkway is at the level a balcony would be at if one existed.
• Doors with closers connect the stage walkway to the audience area walkway.
• A catwalk goes directly behind the proscenium arch.
• A stairway goes up to the beam room above the ceiling where the spotlights are.
• Actors or choir singers can be on the walkways and interact with the audience.
• The aisles at the ends of the rows of seats are under the walkways in the audience area.
• The projection booth has a door to the walkway and a short stairway.
• The lighting console is in the projection booth.
• The lighting patchbay is under the walkway to the left of the stage.
• The cyclorama is between the stage and the rear walkway.
• A walkway is also at the stage level behind the cyclorama under the raised walkway.

Building the Quadraphonic Speaker Setup

This is how the quadraphonic speaker layout was assembled in the auditorium:

• The speakers are F (front), L (left), R (right), and B (back).
• The speaker locations F, L, R, and B are marked on the map of the auditorium.
• The speakers were large speakers made for auditorium use.
• The L, R, and B speakers faced the audience.
• Speakers were raised over walkway parapets by setting them on pairs of wooden chairs.
• The speakers were set so the high-frequency drivers played over the tops of the parapets.
• The F speaker faced downward through the metal catwalk lattice.
• There was enough room for workers to pass on one side of each speaker.
• A zip-cord pair of 18-gage wire was run all the way around the walkway and catwalk.
• The wires were connected to the speakers as shown in the wiring diagram.
• The unused wire in the pair running down the left side was left disconnected.
• Polarity is important when connecting speakers. Polarity was as shown in the diagram.
• The terminals shown at the bottom of the diagram are the amplifier output terminals.
• The amplifier used had common negative outputs (necessary for this system).
• The stereo tape recorder line outputs fed the amplifier.
• The tape recorder and amplifier were in the projection booth.

Building the Encoding Setup

The encoding equipment consisted largely of equipment I already had, plus borrowed tape equipment:

• I had a half-track stereo tape recorder, two turntables, and other equipment (below).
• I had an oscilloscope for monitoring the encoding direction.
• I had a 3-channel system (L, R, and B) used for monitoring the mix.

  - The three channel system produces the same images the 4-channel Hafler system does.

• I borrowed a quarter-track stereo tape recorder to make the final mix on.
• The heart of the matrix system was a small stereo mixer I had.
• This mixer had individual level controls for each channel (no panpots).
• I used a one stage preamp (PA) I had for a phase inverter.
• I used patchcords to connect the various sources and destinations to the mixer.

- Panpots are much easier to use.

- My concept of using a mixer to encode was born.

The Test Tape

I made a test tape containing the following tracks:

• Mono sweep test tones.
• Sweep test tones in the back channel.
• Thunder recorded from a stereo record
• Two more repeats of this thunder
• The same thunder recorded rotated a quarter turn to the right.*
• Two more repeats of this thunder
• The Ballad of John and Yoko (The Beatles) rotated a quarter turn to the right.*

* This quarter-turn rotation was accomplished by:
- Putting the original left channel in the front (in phase in both channels) and
- Putting the original right channel in the back (reversing phase of left channel feed).
- This put material that on the record is centered between the speakers on the right.

I used this tape to set up and adjust the settings on the amplifier.

The Play

Ondine is a play written in 1938 by Jean Giraudoux about Hans and Ondine. Hans, a knight, meets, falls in love with, and marries Ondine, a water-sprite disobeying her purpose. The marriage has tragic consequences.

Encoding the Sound Effects

I was given a half-track mono tape containing the sounds they wanted to use in the play.

I first read the parts of the script having the sounds and voices and a list of the desires the director had for where to place the sounds. He wanted some of the voices to intentionally come from the wrong directions (different from the location of the visible entity) for effect.

I made my first ever quadraphonic pan plot that day. I still use these pan plots for surround recordings today. But I no longer put diamonds or other shapes showing speaker locations in them. I usually use a circle to show the entire sound field.

When I positioned the King of the Sea (KS), I was thinking of the out-of-phase "hole" the theorists said existed there. I wanted the position to be indistinct. But actually trying this positioning with the equipment showed that the "hole" was not the problem the experts claimed. The image was stable where I put it.

I still have those pan plots. But I wrote other things about the play on the backs of the pages the plots were on and the ink bled through. So it was easier to make a new one than to try to separate the wanted material from the unwanted.