> > Has anyone else done this or know anyone working
> > on it??
>
>
> If I remember correctly Philips did a system with specially
constructed
> speakers with 2 voice coils, one doing the driving in the normal way
and the
> other used to provide motional feedback. This was (is?) also a
technique
> used in sub-woofers in High End Car Audio Systems (JVC, I believe).
It
> seemed to be fairly effective in moving the small finite air mass
within a
> vehicle.

Kenwood also did something like that, called 'Sigma drive' to hugely
increase the damping factor of the system. They used four wires for
each speaker connection, two large diameter conductors for the
amplified audiosignal, and two smaller wires to measure the back emf
from the single voice coil. Although technically the concept worked
great, they have stopped using it while there was too much amplifier
damage in the market due to confused customers wiring the system
wrongly. A Dutch (:-)) pro audio manufacturer named Stage Accompany is
still using such an approach with very good results.

Daniel...

--
http://www.piclist.com hint: To leave the PICList
mailto:piclist-unsubscribe-request@mitvma.mit.edu