Re: Why not closed loop speaker amplification?

Jim Thompson <thegreatone@xxxxxxxxxxx> wrote in message news:<rdqba1t7bts3rtgou1iq8d5llp4lhoh0j4@xxxxxxx>...
> On Tue, 7 Jun 2005 19:24:04 +0100, "R.Lewis" <h.lewis@xxxxxxxxxxxxxxx>
> wrote:
>
> >
> >"Kalman Rubinson" <kr4@xxxxxxx> wrote in message
> >news:6hkba1ht2pvoj0uabmsnf92elru4nrsm62@xxxxxxxxxx
> >> On 7 Jun 2005 09:45:24 -0700, bill.sloman@xxxxxxxx wrote:
> >>
> >> >It has been done - some years ago Philips used to sell loudspeakers
> >> >that worked on this principle. They weren't all that good, probably
> >> >because the position of the diaphragm is measured at one point, and the
> >> >diaphragm, not being infinitely rigid, distorts under load.
> >> >
> >> >IIRR Philips used an accelerometer mounted on the drive coil as their
> >> >"position" sensor.
> >>
> >> And it is currently being done on many 'servo' subwoofers.
> >>
> >> Kal
> >>
> >generally referred to as 'motional feedback'.
> >
>
> Or 'emotional feedback' ;-)
>
> What low frequency corner can be achieved this way?
>


As low as you want to, but eventually you will run out of diaphragm
travel and power handling, so you can only go low at the cost of
loudness.

I have an old article with a full design somewhere I'll see if I can
find it,
as far as remember the whole point was to move the low frequency
corner down, achieve a "nice" Q and reduce distortion

-Lasse
.