Seeburg's Quadraphonic Sound Jukeboxes

    The consumer quadraphonic craze started with the introduction of the SQ system by the CBS Technology Center in early 1971.  CBS was a major manufacturer of vinyl records at the time, and many of these were offered with SQ encoding. Full quad was introduced a few years earlier using four channels of discrete audio on reel-to-reel tapes, which had to be played on a special tape deck. This was followed by Receivers and Decoders with built-in SQ circuitry. Evidently, Lafayette introduced the first receiver (their model LR-440) with a built-in Decoder. SQ suffered from poor front-to-back separation (only about 3db, which means twice {+3db} or half {-3db} the power, and is the difference required for most people to notice that the volume has changed), concentrating on improved left-to-right separation instead.

    Sansui introduced a competing (and incompatible) system, called QS, which offered substantially improved front-to-back separation (on the order of 20 db). Over the next few years, they introduced and continually improved their 'Vario-Matrix' system.

    Both of these systems encoded the rear channel information using a technique called 'matrixing' in which a fraction of the rear channel information was shifted in phase by plus and minus 90 degrees, along with 180 degrees, and added to the front channels.  QS differed from SQ in that the fractions are different, and the 180 degree phase shift was not used.

    Due to the way the matrix encoding was implemented, playing one of these records with no decoder simply results in the sum of the left front and left rear channels being applied to the left speaker, and the sum of the right channels being applied to the right speaker.

    Later, another (and significantly improved) system, called CD-4, was introduced. In this system, the rear channels were modulated on a separate carrier, and frequency-shifted to between 35 and 50 KHz before being put on vinyl. Here, the decoder shifts the additional information back to 100 to 15 KHz, the normal audio range. Putting this on vinyl requires a very finely cut groove (requiring special recording lathes) and a special stylus (the so-called Shibata stylus) to track the high-frequency gyrations of the record groove.

    Quadraphonic sound died a premature death, caused primarily by the competing and incompatible systems, and the expense of the extra circuitry (the decoder, two additional power amplifiers and speakers). At the time, the majority of such circuitry was implemented using discrete components, driving up the material and labor costs. Multi-channel stereo in theaters was a significantly better hearing experience, and benefited from standardization, unlike quad. The multi-channel stereo theater experience was finally brought into the home - the so-called 'home theater system' , by the Dolby AC-3, 5.1 channel systems on sale nowadays.

Seeburg's Approach to Quadraphonic SoundImages/sps2_quad_closeup2

    Seeburg wanted to cash in on this craze, too. It meant a boost in accessory speaker sales, a premium price on the jukeboxes so equipped, and an increase in interest by the jukebox playing public, translating to more money in the cashbox for the operators.

    First came a low-production quadraphonic kit to modify the then-current production SPS2 jukebox. It consisted of the SQD1 Quadraphonic decoder, a replacement front graphic panel (shown at left, photo courtesy of Kevin Preston), four bookshelf speakers, and interconnect cabling. A full photo of this machine can be found on the jukebox photos page. At the left is a close-up photo of the top panel of this machine.




    Next was the 'Quadraphonic Seeburg First Edition' machine in 1974, which was identical in most respects to the then-current model year's STD160. This machine was called the SQS160.

    The SQS160 was the first version of the Seeburg Quadraphonic system available from the factory. There were two differences between the SQS160 (at left) and the STD160. The first is the upper graphic panel, as you can see. The second was the inclusion of the type SQD1 Seeburg Quadraphonic Encoder inside. It plugged directly into the cabinet cabling, replacing the connections to the bass speakers in the cabinet base, and the crossover network and tweeter connections, which are part of the installed SN12 Stereo Network.







Images/sqd1_ext    The SQD1 is a small box,approximately four inches (10 cm) wide by 6 inches (15 cm) long by 1 1/2 inches (4 cm) high. This box contained three adjustment controls, and an eight-lug terminal strip, for connecting external speakers such as the LS50 Lighted Speaker Systems being sold as accessories at the time. At left  is photo of the decoder. The original can be found on the Seeburg jukebox information clubwebsite. Note the controls labeled 'Left Front', 'Lt. & Rt. Rear' (Left and Right Rear), and 'Right Front'. The accessory speaker systems connected to the lugs on the terminal strips.



Images/sqd1_internal     This is a photo of the inside of the decoder, showing the three wire-wound potentiometers and the wiring. The original of this photo can also be found on the website listed above. An unadvertised modification made to the factory built units was to have the choke mounted on the preamplifier board disconnected at one end. This choke serves to make the amplifier monaural at low frequencies, an attempt to minimize audio feedback into the amplifier. Since the console speakers were disabled as part of the installation, the choke was no longer needed. Chances are this modification was actually performed on very few of the factory-supplied units.



     The same decoder was used on the SQS2 Quad Entertainer (below left) and SQS3 Quad Sunstar (below right). In the Sunstar photo, you can just see the graphics panel of an LS50 in the upper right corner.

Images/sqs2 Images/sqs3















    Below is a publicity photo of the SQS4 Quad Mardi Gras. I am not sure any were ever offered from the factory, or even if a field conversion kit was available. If you have any information about this, please email me.


    In addition, there was an SQD2 Quadraphonic Decoder, designed for use in the FC1. I have never seen this unit, but I'm sure it is identical to the SQD1, except for the cable connections. The cable connections are different from those used in the other machines since a different Stereo Network (SN11) is used in the FC1. It may have been identical to the SQD1, with an extension cable included. Field update kits were available for both the FC1 and FC2 machines. These kits probably included some sort of graphics panel to set the machine apart from the normal version. If anyone has one of these, please send photos!

    Only a few SPS2 jukeboxes were modified to use the quad adapter. The SQD1 pictured above was used in the SQS160 and later jukeboxes. The SPS2 quad conversion actually used a metal project box to house the circuitry, which was riveted shut and also riveted to the machine's lower rear panel, just inside the rear access panel. See the photos below, which were provided by Jeff Ziemer. In the right hand photo, the gray cable with round, black connector plugs into the side of the decoder. The barrier strip on the other end of the cable is used to connect to the external speakers. The black cable is used to connect a PRVC to this machine, and has nothing to do with the quad decoder.


    What was inside the box, sealed with tamperproof screws?

'Under the hood' of the SQD1



At the left is a schematic diagram of the SQD1. As you can see, it's simply three potentiometers, connected between the amplifier outputs and the speaker terminals. The two connectors (the 3-pin and the 5-pin plug into the cabinet cable, and replace the stereo network connections in the normal machine. The machine's internal speakers and the stereo network are not used.  The red wire of the 3-pin connector comes from the amplifier Left Channel output connection; the Blue wire of the 5-pin connector comes from the amplifier Right Channel output connector. In the normal machine, these wires connect directly to the Left and Right channel woofer speakers, respectively. The Wht/Red and Wht/Blu connections (which are part of the SQD1 input cable) are not used in the SQD1, and are perhaps a bit of subterfuge on the part of Seeburg. In the normal machine, they connect to the Left and Right channel horn tweeters, respectively.

    How does it work?






   This is how it's connected to the speakers. Note that the 'Lt Front' and 'Rt Front' potentiometers are connected in series with the front or main speakers. They simply serve to control the relative volume between the front and rear speakers. The rear speakers are connected across both amplifier output channels, with the 'Lt & Rt Rear' control connected between the common connections of the rear speakers and the amplifier common output terminal. Connected in this manner, the Rear speakers will only output the difference between the Left and Right amplifier outputs. The 'Lt & Rt Rear' potentiometer controls how much of this 'difference' signal you hear. With it set to 0 Ohms, all you hear is the amplifier Left and Right audio. With the control set for maximum resistance, you get the maximum effect. This simple circuit was invented by David Hafler (U.S. Patent #3,697,692), and was licensed to the Dynaco Corporation by him. In fact, he was the founder of Dynaco and one of the main designers of most of their amplifiers, renowned in the 50s, 60s, and 70s for superb high-end audio systems. This simple circuit recovers the rear ambient sounds such as audience coughs or applause, which the recording microphones generally pick up in opposite phase to what is generated by the musicians. Also picked up are echoes from the recording location. All this adds to the ambience or realistic sound of many recordings. The effect will vary from record to record, but the operators simply set the controls so that the average record sounded okay, and left it at that. I'm not sure you would hear much difference in the typical place where you would find the jukebox. It seems to me you would have to listen in a pretty quiet environment to pick up any rear channel sounds. Home installations would certainly sound much better than the typical bar or restaurant.





Other Seeburg Quad efforts

    As a follow-on to the Hafler Quad system, there was an effort to incorporate matrix-decoded quadraphonic sound into the jukebox line. While I worked in the Engineering Department, a project was started to determine what changes would be required to incorporate matrix quad sound. Examples of both SQ and QS decoders were obtained, and a comparative listening test was set up in our audio demonstration room. I was not invited to any of the sessions, since I was not a high-powered executive, but I did help in the setup and attended the informal Engineering demo that occurred prior to the big shot's session. We Engineers were unanimous in thinking that the Sansui QS Vario-Matrix system was superior to the others, except for CD-4. This latter system was not seriously considered, due to the major tooling effort required on the part of both Seeburg (to significantly reduce the tracking force of the pickup arm) and Pickering, the cartridge supplier (to totally change the contours of the stylus, and increase compliance substantially to be able to handle 20 - 50 KHz audio). For the matrix system, the cost of the decoder, two more channels of amplification, and the licensing fee for whatever system was to be used proved to be more than management thought the operators would pay, and this version of quad died, too.

    Thanks to Ron Rich for providing many of the details that went into this article.

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