Well, I can think of other reasons why it failed at that time. First, confusion in the marketplace over the competing LP formats. None of the major formats (QS, SQ, CD-4) were completely compatible with each other. QS and SQ could be played on the other's decoder, but rear channel sounds would be imprecise. CD-4, played through one of those decoders, would be like a stereo record played that way. And a CD-4 demodulator would see a matrixed record as stereo, without the carrier signal that makes it work. Second, the "WAF" (wife acceptance factor). Two speakers were bad enough; four? "Not in MY living room you don't!" (Notice how the wives always take ownership of the living room, or anything that affects their decor?) I find that one even now when selling a surround system. Third, apathy among retailers. Many had no idea how to present it to the customer, how to properly demonstrate it, and how to answer customer concerns. Worse, they didn't care. When quad made its reappearance in the form of surround sound for movies, this time we had some standards. As the technology evolved, newer formats and techniques were developed, and were quickly embraced by equipment manufacturers and film studios. They found these techniques worked for music, too. You know the rest.