Back in the 80’s or early 90’s I purchased information on how to built a SuperWoofer from Cheney Innovations. I have no recollection how much this cost, or even where I got it from (but I suspect in was in the back of a Stereo Review magazine).
I cannot find any info about Steven A. Cheney, or Cheney Innovations, so one could assume that the company did not flourish.
Here is a searchable PDF of that document I purchased. Note that all hand written information came from the author, I did not write on these pages.