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Quote:
Originally Posted by sputter1
As as a guess, it sounds like some kind of servo setup.
I seriously doubt that being its a $100 sub... Probably more like what the OP suggested "something to help prevent the woofer from blowing".
 

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Just completed a brief search and this is what I found in Sony's explanation of this Motional Feedback technology (according to the patent they were awarded way back back in 1996!)...

A loudspeaker apparatus includes a diaphragm, a driving part driving a diaphragm, a detecting part and a coupling member. The driving part includes a voice coil bobbin mounted on the diaphragm, a voice coil wound about the voice coil bobbin and a driving magnetic circuit generating a driving power driving the diaphragm along with the voice coil. The detecting part has its terminal voltage changed responsive to the rate of displacement of the diaphragm or the voice coil bobbin. The detecting part has a detection bobbin about which a detection coil is wound and a detection magnetic circuit for detecting displacement of the diaphragm or the voice coil bobbin along with the detection coil. The connecting member is cup-shaped and formed of a liquid crystal polymer material. The coupling member has its surface smoothly curved from the outer lateral side towards the center. The coupling member has one of the voice coil bobbin and the detection bobbin mounted on its outer peripheral surface and the other of the voice coil bobbin and the detection bobbin mounted on its mid portion. The driving part and the detection part are arranged coaxially. A detection signal of the detecting part is fed back to the driving part.


From that description it sounds to me a lot like the way Rythmik is doing its direct-servo sensing... I also found reference to Phillips also having used this "Motional Feedback" (their terminology) in speaker design some time ago in the past. So YES, it does appear to be a servo system... and for less than $100!


Out of curiosity I decided to search just a little further and found out that evidently there was a patent filed way, WAY, WAY back in 1974!!! on this technology, here is a description of it...

A sound reproducing system utilizes motional feedback to reduce loudspeaker distortion and to extend the loudspeaker's frequency response. The system substantially comprises an amplifier which is jointly responsive to the input source signal and to a feedback signal, a moving-coil loudspeaker including a main electromagnetic structure which is responsive to the amplifier's output signal for effecting axial speaker-cone motion, motional sensing means for providing a signal which is functionally related to axial cone velocity, and an equalizer exhibiting a predetermined nonlinear attenuation versus frequency characteristic and which is responsive to the motional signal for providing the feedback signal. The feedback signal is degeneratively applied to the amplifier which, in turn, forces the loudspeaker to respond linearly to the input source signal and thereby provide a uniform sound energy output. It is a feature of the present invention that the loudspeaker cone exhibits a substantially constant acceleration at low frequencies and a substantially constant velocity at higher frequencies.
 

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Sorry to revive a really old thread, but I recently bought the Sony SA-W3000 for about $110 from Frys, and it sounds quite good!


So, is "Motion Feedback Technology" really servo control?


If so, isn't it quite a deal?


I am considering purchasing 1 more of this subwoofer, as opposed to spending about $300 on a 12" RW-12d Klipsch.


Would love to get feedback from folks with good subwoofer experience.


Thank you!


ps: I do care more about clean bass for music, rather than glass/wall thumping boom for HT - if that helps clarify what I am looking for.
 

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I used a couple of these Sony subs (12" version) to test placement for my

infinite baffle in-floor subs.

I came away quite impressed with the sound they provided for the price.

They didn't dig much below 30hz, but what do you expect for that price?
 

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A servo provides feedback to the amplifier. So this kind of feedback is different but it's still some kind of feedback system.


90% marketing 8% markup 2% improvement? Kidding. I have no idea how effective it is but sounds promising.
 
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