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KEF's Breakthrough VECO Speaker Technology to Lower Distortion–Explained by Its Inventors

sigbergaudio

sigbergaudio

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(From the Youtube description)
KEF's latest innovation in speaker technology, VECO (Velocity Control), is revolutionizing active speaker performance. In this in-depth interview, KEF's VP of Technology Jack O'Clee Brown and R&D engineer Prathmesh Thakkar reveal how combining a current-drive amplifier with a custom-designed velocity sensor leads to unprecedented control over driver motion, slashing distortion and enhancing clarity.

 
Current drive is as old as (active-ish) speakers matched with their tube-amps.
I guess, if it worked back then it should work now even better.
 
Sokel said:
Current drive is as old as (active-ish) speakers matched with their tube-amps.
I guess, if it worked back then it should work now even better.
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Certainly has worked well in Rythmik and Velodyne subwoofers.
 
Curvature said:
Motional feedback? About time a bigger brand has picked it up.
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I would surmise that Philips, a much larger brand than Kef (and by far: About 250 times larger ), had a line of MFB speakers in the early 1970 .. My recollection was that they sounded surprisingly good...

But Kef is dedicated to audio .. and has the stellar products to show it so...
We'll see

Peace.
 
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Hmm, looking interesting...

Looking at my crystal ball - Blades with this new tech, brand new BMW M3 or put your kid through college?
 
FrantzM said:
I would surmise that Philips a much larger brand than Kef (and by far: About 250 times larger ) had a line of MFB speakers in the early 1970 .. My recollection was that they sounded surprisingly good...
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I even have one of their TOTL models in my collection and enjoy it from time to time still today, it should be said though that the MFB models were not sold in large quantities despite the big brand behind.
 
I have long wondered why so few companies offer speakers whose drivers are actively monitored and controlled by sensors.
Backes & Müller and Philips did this decades ago, but unfortunately, although the advantages are immense, the principle has not caught on.

I am very pleased that KEF is integrating a modern version of sensor control into its speakers.

Very, very good and well done KEF
 
Audionaut said:
although the advantages are immense, the principle has not caught on.
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I think it's debatable whether the advantages of servo controlled drivers are "immense".
 
Motional Feed Back again. What makes the sound is the acceleration, not velocity. The sensing is indirect. The design of the sensor may imply limitations like max excursion. Purify suggested and used a tweeter, placed inside the box, as a pressure sensor. So, to measure the grand total of output works with reflex also.

Presumably we won‘t see that VECO tech/ with other, more reasonably sized speakers soon. The drivers those use are, even before the ‚meta‘ revolution, pretty much close to perfect. Dunno what to improve for regular people.
 
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Seems like it would be simpler to use something like a bar code reader to detect cone motion. Could be retrofitted to existing drivers,
 
Audionaut said:
Backes & Müller and Philips did this decades ago, but unfortunately, although the advantages are immense, the principle has not caught on.
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If I am not mistaken, the founder of B&M has still an operating company called Silbersand employing the very sensor technology they invented in the 1970s. B&M still uses a similar principle as well at least for subwoofers and bass drivers, and so do other manufacturers.

Interestingly Müller´s solution of an electrodynamic velocity sensor seemingly circumvents most of the problems KEF has claimed to solve in a pretty complicated manner. His sensor coil is not following the shape of the voicecoil former (which would pose induction problems), but uses two separated windings on a little plate, placed in the middle of the voicecoil kind of crossing this area:

BMSensor.jpg


Sensor control service

sigbergaudio said:
I think it's debatable whether the advantages of servo controlled drivers are "immense".
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Yes, I would not overestimate the advantages such a sensor and negative feedback loop can bring, but I would say they can be significant in a limited frequency band under certain conditions.

It might be interesting how that would affect the concept of active speakers as the general opinion expressed by developers using sensor technology already is that it does not make sense with bass reflex concepts, drivers with limited excursion capabilities and DSP crossovers with significant latency. Sounds to me as if a radically different active concept has to be designed around this little sensor.

Heinrich said:
What makes the sound is the acceleration, not velocity. The sensing is indirect.
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Which is not really a problem to implement in a negative feedback loop if you know how these parameters are depending on each other.
 
Arindal said:
Interestingly Müller´s solution of an electrodynamic velocity sensor seemingly circumvents most of the problems KEF has claimed to solve in a pretty complicated manner.
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Yes, but aside from looking like a tinkering solution not ready for industrial scale this is not exactly what you want for a coax driver ;-)
(though it is not clear into what kind of driver this is supposed to go)
I would not hold my breath to long about a velocity feedback solution anyway as this will probably produce only moderate improvements unless KEF found something revolutionary. (Oclee-Brown speaks about lowering Q which is what one would expect)
Proportional Velocity Feedback, which creates a force that counteracts movement. As this force is proportional to the velocity it acts like a mechanical damper, reducing the Q of the resonance (the yellow arrow). This is favorable, however hardly other beneficial effects on for instance distortion are noted as the effect is limited to the resonance frequency region. (Rob Munnig Schmidt)
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A very short overview over MFB techniques (concepts, advantages and disadvantages) by someone, who clearly knows this stuff, can be found here.

Active Controlled Subwoofers

Active control of low frequency sound systems
www.rmsacoustics.nl www.rmsacoustics.nl
 
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Arindal said:
Which is not really a problem to implement in a negative feedback loop if you know how these parameters are depending on each other.
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Regarding the sense being indirect, it was meant to direct towards measuring the whole speaker‘s output with the internal air column’s pressure as a proxy. Such might work with reflex also. Of course its use is limited to bass, whilst sensing cone motion is not (with low inductance drivers).
 
The concept has been around a long time, what has not was a sensor that was economical and which worked well enough.

This looks like a clever solution to making a reasonable job of the bass in the new sound bar or helping a 2-way uni-q.
Rather than a breakthrough where size and cost constraints are much less challenging.

Looks v clever to me, I say bravo.
 
mhardy6647 said:
Yeah, Philips was kind of a mom & pop store in the 1970s, weren't they? ;)



There's been a lot of breakthrough inflation in the past 3 or 4 decades.
:rolleyes:
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"Picking up" the bit dropped by others for a long dusty time now.

Kind of like Purifi and their complex surrounds. Also not new, but certainly better than older iterations.
 
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