Examples of DIY motional feedback?

[qwad]

Hi!, you should check through past issues of "hi-fi world" magazine where some yrs ago Noel keywood discusses the very same subject and ways of doing it in a practicle way, I have most of them unfortunately having recently moved everything is in a total pandemonium, anyhow it transpired that even the erstwhile P. voight filed a patent on a proposed mfb system back in the '30s !, sorry I* can't be more help but it does offer you another avenue of investigation.... in the end mr keywood concluded the idea was not very practical from a diy point of view as he witnessed his prototype self destruct before his very eyes....... btw, phillips used piezo acceleration devices attached to the voice coil s of their systems of the llate 60's mid 70's, cheers TC