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Trevor Wilson[_3_] Trevor Wilson[_3_] is offline
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Default Motional feedback in speakers

On 8/11/2019 6:32 am, Mat Nieuwenhoven wrote:


Interesting story. I had two of the smallest Philips MFBs a few years
back, was not impressed with the sound.


**I've never lived with a pair, but was always impressed with the quite
decent sound quality from the Philips MFB systems.


Regarding feedback, I remember there was an hobby project long ago to
have a very small R between speaker and GND (GND also being the amp's
ground), and using the speaker's back EMF as feedback to correct
excursions. There are some later publications from W.Kippel about it.


**The first system I saw with that arrangement was the Infinity RS1. It
introduced as many problems as it solved. Amplifiers with 'floating'
output stages encountered some problems. Bridged amplifiers too. That
said, the bass extension available from a rather modestly sized, sealed
enclosure was impressive.

The idea is that the speaker's voice coil itself is the sensor. Will
this feedback method work?


**I can attest that it certainly works.

And only for closed boxes, or for
bassreflex also?


**I would have thought that such a system works best with the simple
roll-off available with a sealed enclosure. I guess with sufficient
modelling and appropriate filtering, it should be OK with more complex
enclosure types.


--
Trevor Wilson
www.rageaudio.com.au