2x amp, 2 inverted electro-coil magnets = speaker [II]

[petemoore]

  Rather than try to straighten up the old thread...

 Speaker coils are not that close usually but probably do 'couple' to a tiny immesurable or inconsequential amount.
 I want to make 2 separate but very adjacent [similar to the way a coil is adjacent a fixed magnet] coils react with opposing electromagnet forces while driven by 2 amplifiers.

 Driven by battery of course works.
 
 I'm just wondering how much like coupling 2 amplifier outputs through an electromagnetic interface like this will damage the standard amplifier.
 
 ..and how to make amplifiers which won't be damaged by experiments in such manners.
 ...I imagine the same thing happened with the first speaker/amp...oh...it's gonna put a load on the output ! !...fried outputs later...amp that can withstand the loads became known.
 Same thing here except some unknown history:
 Is there any history of dual electromag-speaker near the beginnings of all speaker designs such as field coil speaker.
 Because it seems to me to be nearly the same exact thing as a field coil speaker except for the 2x amplifier requirement [which would put the fixed electromagnetic field magnet in good 'go to production' standings].
 Anyone else know anything about the history...
 Forgotten about ?
 Never tried ?
 Tried and deemed impossible ?
 Tried and deemed undesirable [for what reason then] ?