Here's a thought

[smowry]

I posted the question of why we cannot seem to commutate the transducer's voice coil? There are patents but no products. One obvious issue is that the voice coil is dynamic, it moves. Then what if we commutate an EMI dive, where the primary coils would be stationary and a single turn coil (shorting ring) is driven via induced current. This is sometimes referred to as transformer drive.
https://www.linkedin.com/pulse/radial-emi-transducers-et-al-steve-mowry/?trackingId=BJ2JhX2KSma72lWZfOzy%2Bw%3D%3D

A control system would be required to assign the appropriate signal to the respective stationary coils. It seems that we have the technology but do we have the will?

FAQ: Why would we want this?
1. Large Signal Distortion reduction
2. Increased Transducer Efficiency
3. A potential pathway to the digital transducer

 

[Chrispy]

I'll say it's beyond my pay grade but sounds somewhat insane. Staying tuned in for education....

 

[smowry]

I'll say it's beyond my pay grade but sounds somewhat insane. Staying tuned in for education....

Well there maybe a superhero or two out there but typically such a project would require a development team.

 

[Chrispy]

Well there maybe a superhero or two out there but typically such a project would require a development team.

Damn wasn't expecting an expansion...

 

[kemmler3D]

Doesn't sound insane to me, but I think the control system would have to be pretty beefy.

At CES almost 10 years ago, I saw a booth that had a very high resolution electromagnetic force feedback device. They pitched it as being for the gear shifter in driving simulators, stuff like that. However, I thought it was pretty interesting for audio, because it could move pretty well at audio rates, albeit LF. They were able to do all this in large part because of the computation behind it.

So I think it sounds doable, at least for woofers?

 

[smowry]

EMI Patents to date:​

Sony has spent much time on R&D and they have several patents that discuss and develop the theory for the above.

1. www.freepatentsonline.com/5062140.pdf

2. www.freepatentsonline.com/6904158.pdf

3. www.freepatentsonline.com/7016515.pdf

4. www.freepatentsonline.com/7580542.pdf

Klipsch also has two Euro Patents on EMI drivers.

5. www.freepatentsonline.com/EP0453130A2.pdf

6. www.freepatentsonline.com/EP0453130A3.pdf

Then there is Tannoy’s co-axial.

7. www.freepatentsonline.com/4965839.pdf

I found another US Patent issued to W. K. Volkers in 1950.

8. www.freepatentsonline.com/2494918.pdf

I found another US Patent issued to S. E. Karlsson et al. in 1950.

9. www.freepatentsonline.com/2621261.pdf

Finally, the oldest Patent that I found was issued to A. Nyman in 1927.

10. www.freepatentsonline.com/1643169.pdf

The latest EMI Patent for a subwoofer motor is here.

11. www.freepatentsonline.com/US8009857.pdf

Now how many EMI transducers are utilized in commercial loudspeaker systems today?

 

[smowry]

Commutated Voice Coil Patents:

1. US8284982 Positionally sequenced loudspeaker system by Adam H. Bailey, filed 6 March 2007, status: Expired - Fee Related

2. US5748753 High power audio subwoofer by Robert W. Carver, filed 2 January 1996, status: Expired - Fee Related

3. US4531025 Loudspeaker with commutated coil drive by Thomas J. Danley and Charles A. Rey, filed 19 March 1984. status: Expired - Lifetime

 

[Heinrich]

... the primary coils would be stationary and a single turn coil (shorting ring) is driven via induced current. ...

FAQ: Why would we want this?
1. Large Signal Distortion reduction
2. Increased Transducer Efficiency
3. A potential pathway to the digital transducer

Position of either moving coil is dependent on a few parameters, think of bass reflex, introducing a tightly coupled, yet uncontrolled device, the port namely. To predict position would be hard, losing track quickly. So it would need a position detector, not the least because of nonlinearities elsewhere. The 'switching' would be embedded into a feedback path. But switching won't be the way to go, except it being, in time and amplitude, fine grained digital. Analog it might be a more gradual shift from one driving coil to the other. That would cost attenuation losses (sorry, language barrier, think of AB amp efficiency). The latter diminishes the power savings.

 

[smowry]

Control System Patents:

Samsung claims a control system invention, US 10,506,347 B2 NONLINEAR CONTROL OF VENTED BOX OR PASSIVE RADIATOR LOUDSPEAKER, filed 17 January 2018.

I have never seen this number of references within any loudspeaker related patent document. Somebody did their homework!

 

[smowry]

Marshall Buck et al. have a EMI design with the patent rights assigned to Wisdom Audio. They utilized the Aura Systems radial magnet motor topology from 30 years ago for the basis of their EMI transducer implementation. https://patentimages.storage.googleapis.com/11/98/00/ba76c730106785/US5539262.pdf

Aura Sound motor assembly less the voice coil, taken from https://www.audiosciencereview.com/...ds/aurasound-ns15-992-4a-motor-exposed.22598/.

Buck et al. patent image shown below.

One is analogous to the other. Each have radial Neo magnets, single turn coils, and multi-turn coils. The differences are that in the Aura the primary (voice) coil is suspended and the single turn coil is stationary, while in the Buck et al. assembly, the primary coil is stationary and the secondary single turn coil is suspended.

There is a similar but perhaps better option, the Vivid Topology.

Taken from https://www.linkedin.com/pulse/radially-speaking-steve-mowry/?trackingId=9cLAYbZsQZqWShfaUA0+rA==

The Vivid Topology has two primary advantages.

1. The magnetic gap width is significantly reduced.

2. The primary heat source, the primary coil is moved away from the magnets.

Then using the Vivid topology for the EMI drive would simply make the primary coils stationary and suspend a single turn secondary coil. The magnets would be positioned below the gap as shown above.

The proposed update is to segment the primary coil of EMI drive and to actively control the coil segments.

 

[tktran303]

We probably have to ask Mr FSAF to come out and play with us. The main thing is we all need to collaborate and work together. You need the people who have been doing transducers, amplifiers, cabinet, control theory, industrial design, who know math and physics better than the rest of us, but also to communicate better than the rest of us. And stop dodging questions like the best politicians or CEOs when they don't know the answer.
It's OK to say... oops, I don't know... when I do I will get back to you on that. How do we all respect each other and work towards a common vision/fiction?

Half the time people don't can't even see eye to eye on the most basic things. To make a speaker more linear-time invariant he proposes an adaptive filtering technique that doesn't cost the earth in compute. But why should we (society) do that when we can't even get the basic things like the size or shape of the spider right (that doesn't cost much) or can't agree between 1, 2 or 3 roll surrounds, and the only neutral-ish surround is locked away by patents for the next 20 years?

What is the sound of one hand clapping?

Turns out it's quieter than the sound of a flappy surround or a funky junk spider.

Just keep cranking up the fancyllium on the cone/dome and carry on...

 

[smowry]

Buck et al. used a proprietary mixture of iron powder and a polymer, whereas, solenoids typically use 430F Stainless Steel. The 430F has good magnetic properties but has high electrical resistivity along with excellent corrosion resistance. The Vivid topology requires just two 430F parts, ID and OD rings. Typically moving coil transducers utilize 1010 steel for the high permeability motor parts but 1010 is about 4 x more electrically conductive than 430F. In practice the 430F parts would simply need to be made thicker relative to the 1010 to achieve the same level of flux in the gap.

BH Curve of Magnetic Stainless Steel

BH Curve of 1010 Steel

 

[smowry]

"Say hello to my little friend."

Section view of EMI drive motor concept sketch with segmented primary coil.

Patent image from Bob Carver's dream from US5748753 filed 2 January 1996.

 

[smowry]

The magnetic gap is very tall and the flux density will tend to be reduced as the one turn coil moves away from the magnets. Then a axially magnetized "cheater" disk magnet can be positioned on the center pole piece. Back in 1999 in Malaysia, Dr. Godehard Guenther used to call that a "turbo" magnet.

By using FEA to simulate the assembly above, a linear DC flux density linkage Bl(x) should be possible. The geometry is actually quit simple.

 

[srrxr71]

I posted the question of why we cannot seem to commutate the transducer's voice coil? There are patents but no products. One obvious issue is that the voice coil is dynamic, it moves. Then what if we commutate an EMI dive, where the primary coils would be stationary and a single turn coil (shorting ring) is driven via induced current. This is sometimes referred to as transformer drive.
https://www.linkedin.com/pulse/radial-emi-transducers-et-al-steve-mowry/?trackingId=BJ2JhX2KSma72lWZfOzy%2Bw%3D%3D

A control system would be required to assign the appropriate signal to the respective stationary coils. It seems that we have the technology but do we have the will?

FAQ: Why would we want this?
1. Large Signal Distortion reduction
2. Increased Transducer Efficiency
3. A potential pathway to the digital transducer

Finally I got a clue what a digital transducer could be. I suppose each bit value would have a certain current value attached to each of possibly 7 coils windings or so. Sort of like an R2R DAC in reverse. Each coil winding would be have to be independently driven. That sounds very expensive but I’d rather try that than some $30k phono cartridge thing.

 

[HalSF]

There is a 100% chance I never would have opened this thread if the title have been, “Why Can’t We Commutate the Transducer’s Voice Coil?” instead of “Here’s a Thought.”

 

[srrxr71]

There is a 100% chance I never would have opened this thread if the title have been, “Why Can’t We Commutate the Transducer’s Voice Coil?” instead of “Here’s a Thought.”

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Once you hear state of the art loudspeakers you begin to realize we’ve way past the point of diminishing returns at this point. Then you realize the only place for improvement are thoughts like commutating voice coils and the like.

It’s just fun reading at this point. It’s not like the anticipation we had for new advancements back in the day. I would perfectly fine if no major advancements happen in my life time. Sit close. Treat your room. Done.