The Quadfather

Actually, in CD-4, the front channels and the rear channels are the same quality. During the encoding process, the front channels are mixed with the rear channels in phase and recorded as the main audio on the audible part of the bandwidth. In this way, if you played it on a stereo system, you would experience it as a stereo record, and all the musical elements would be there with left/right separation maintained by vector modulation same as stereo. The subcarriers, there were two, one for each of the two channels, were separated and sent to two channels of demodulation. After demodulation there was ANRS noise reduction, a system similar to Dolby B. These subcarriers are the difference signal generated by mixing the front and rear channels out of phase, this is the separation information that is used to reconstitute the original four channels. To do that, the separation signal is mixed in phase with a sample of the main signal, and the rear signal is canceled out because it was out of phase when mixed in the modulator. This leaves only the front channel which is sent to the output. To get the rear channel, the same two signals are mixed, but the separation signal is mixed out of phase, so that the front channel audio is cancelled out leaving the rear channel signal which is sent to the output. Never are the left and right sides intermingled. So the result is that all four channels are the same quality.And the quality can be pretty good with the right setup. There is delay compensation in the modulator designed to correct for the natural delay in the demodulator. This was done to make the demodulators less expensive because they would not need to have their own compensation. CD-4's best performance was finally realized after the quad era, with the development of the microline stylus, or linear contact, a Shibata variant that performed better at tracking the finer modulations of the subcarrier frequencies. The CD-4 system is similar to FM stereo, except that FM stereo does not use noise reduction for the subcarrier. With SQ and QS and other matrix systems, the left and right channels are intermingled, but they do start out as four independent channels. The encoders mixed the four channels into the two channels of stereo at different phase angles, which the decoder would try to extract. The problem was that the decoders could extract some separation, but not enough. It wasn't until the Tate system was developed that serious separation performance was realized for SQ, and Variomatrix for QS, but by that time, quad was commercially dying. It also didn't help that every cheapo stereo manufacturer had a fake quad system which consisted of a stereo with a Hafler circuit and a "quad" button, that made it sound different, but wasn't true quad.Many people thought they had heard quad, but never did.They were disappointed, of course. The Quadfather

Note that DVD Audio and SACD's are still being released, but very slowly. It's a niche market. The Quadfather

The FCC did not approve a quad broadcast standard until long after the demise of quad. Too little, too late. However, SQ and QS recordings could be played over stereo FM and not lose the encoding if the compression was not too heavy. Those systems worked by mixing the four channels onto two channels using phase shifting techniques. The decoder was supposed to be able to extract the four channels by reversing the encoding. For most decoders, it didn't work well. Toward the end of quad, the Audionics Space and Image Composer was developed, and it was able to separate the channels quite well. Later, the Fosgate decoders came out using the same "Tate" system. They were also good. The Sansui Variomatrix QS decoders were known to be very good,and Lafayette made a decent SQ decoder, I am told, though I have never heard one. QS and SQ were different, and while you could use one decoder for the other system, it didn't quite come out right. CD-4 records have supersonic subcarriers, and if played in an FM studio, would come out as a stereo recording. If demodulated, it would yield four discrete channels, but that could not be transmitted over the radio unless encoded in SQ or QS. These are the records that needed special cartridges that could track the subcarriers. A four channel recording from CD-4 is barely distinguishable from a DVD Audio 5.1 setup, if you exclude the obvious lack of record noise on the DVD. It can sound quite good. The four channel system can image the center speaker much as a stereo setup can. I bought my quad setup in the late seventies, and I still maintain it. I have added 5.1 DVD Audio and SACD, and video. This was easy to do since I used separate stereo amplifiers. But sorry, Klipsch, I used JBL speakers. But I do respect your speakers, their reputation is well known. I do say that if you want to be a quaddie, it helps to be an electronic engineer, because the old equipment requires more maintenance than new gear. Even if you do use newer gear, the decoders and demodulators will have to be vintage. That Pioneer receiver dtr20's father has will probably need some capacitors replaced. It would be better to find an older repair tech that remembers quad, I would expect that most of them are retired by now. Good luck. The Quadfather

Dear dtr20: I was checking out the web for "other" quadraphonic sites, when I ran across this Klipsch site. I can answer your questions and steer you in the right direction. Quadraphonic is much more than double stereo using splitters. The premier quad website is QuadraphonicQuad.com, and there you will find the quad community, and much modern and up to date information about legacy quad and modern multichannel surround sound for music. As stated above, quad was a bit of a fad, but it was a long running one, and much music was produced in quad. So if you like 70's music, it would definitely be worth checking out. Quad had a lot of technical problems to begin with but most had been worked out by the time of it's demise, and some worked out even afterwards. That Pioneer QX949 was a fine receiver, but the Pioneer SQ decoders weren't very good. The separation was poor. If I'm not mistaken, that receiver also had a CD-4 demodulator built in. CD-4 demodulators required a good signal, and most of the cartridges of the day weren't capable of providing it. Modern microline cartridges made by Audio Technica perform well. I use the AT 440MLa. The AT440MLb works equally well, although neither is "rated" for quad, listing a frequency response that falls far short of what is required. AT does have cartridges that rate up to 50KHZ if you want to spend the dough. As for turntables, they just have to have low capacitance wiring. Most high quality turntables of the day qualify. (look for thick "video like" cables). And as for CD-4 record wear, that's a myth. In the early development of CD-4 that was a problem, so JVC developed super vinyl, which was used from that point on. All my CD-4 albums play with separation intact.If you or any of these other folks want to learn more about quad, check out QuadraphonicQuad.com. It's worth pursuing if you like multichannel music. The Quadfather