In fact they worked so well that I never understood why they stopped making them. I now suspect that they got the Leslie's barking at them about infringement. I was so taken with the idea that one of the first things I did at Bell Labs was have some guys "witness and understand" a page where I described a way to accomplish the same thing without spinning the speaker. I didn't do anything with the idea for various reasons. Now I recently saw where someone else patented the idea and is selling it - 54 years later. Dick