KentT wrote:CD-4 was a pain in the rear end. And in 1970's mass market, oil crisis era vinyl production USA vinyl real life, not a doable system. The records had to be 1/2 speed mastered, needed to be made in Japan on JVC Super Vinyl for them to have lasted very many playings (which would have been $13 each) and also were limited to 15 Khz top response. Open reel tape was the best format for discrete Quad. Sansui's QS was the only system which could be used on average phonographs, the best of the matrix formats, and the only system ever practical for FM broadcast, the only truly backwards compatible format with Stereo, and practical for the US Record Industry to implement CD-4 was not practical, broadcasters hated SQ (phase problems for them), and backwards compatibility was necessary for single inventory LP and 45 RPM sales.
Quad sound only lasted a couple of years, it fell out of favor due to its confusing use and questionable quality, along with the costs which people didn't find worth it.
It's funny, but when it first appeared on the scene back then, I KNEW it was lousy and wouldn't last.
And I was right.
The bottom line: it was a "fad", a marketing gimmick, to hopefully boost the income of manufacturers.