Magnetic or Bose suspension

I was just reading about the new mid-engine Corvette and noticed talk of the magnetic suspension.

Magnetic suspension uses something familiar to speaker builders - ferro fluid - and active control (with feedback from all four corners of the car) instead of just unsmartly pumping oil around inside shock absorbers*.

There is also the Bose suspension using a linear induction motor and some real smart computing that controls the car ride.

In recent years, there have been drivers made with linear induction motors and with synchro stepper-like motors. Not sure where they stand today.

So I wonder if there is an application of this active control thinking to driver design comparable to motional feedback which controls the voice coil signal?

B.
* OK, modern shock absorbers are really quite brilliant bits of mechanical ingenuity
 
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I share your reservations about car audio, but my OP was about getting feedback around the woofer, not just to do with playing music in cars.

I guess it is easy to substitute "driver" for "driver", eh. My bad.

And really weird that Bose (that Bose?*) developed the automobile suspension system.

B.
* Amar Bose was quite a technical whiz and MIT professor for 45 years, whatever you may think of the the products made by his Bose company. Likewise for "Dayton-Wright" of ESL fame. And then there's that smart fellow who recently went from MFB speakers to LIDAR on smart cars
 
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TBTL

Member
2013-10-08 12:26 pm
Linear induction motors should result in a long stroke woofer, without having most of the energized coil outside of the magnet gap. I guess nobody makes them, because wasting power in a coil outside of the magnet gap is not expensive.


The closest thing is the servo sub by Danley.
 
Wasn't the Danley thing was meant to create super-low audio (or sub-audio)?
Danley's "servo drive" subs were made in a variety of formats for PA and home use, the "Contra Bass" had a -3dB response of 15 to 125 Hz, 114 dB at 16Hz at 1 meter, quite impressive for it's size (around 8.5 cubic feet) back around 1987.

That technology was the basically the inverse of a linear induction motor, the "servo drive" used a brush-commutated, low-inertia servo motor coupled with belts and drive arms to convert it's rotary shaft output to the linear "in and out" motion of typical loudspeakers.
 

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The servo-motor concept is cumbersome even it is one route to tremendous and very low emanations. Even if you can buy servo-motors with excellent linearity, still all the moving parts might make it worse than the Rice-Kellogg yo-yo system in current use.

With a ferro-fluid shock absorber, you'd have a "motor" of some kind and then motional feedback that would modulate the ferro-fluid in real time to get the cone placed exactly where it should be at each instant in time.

B.
 

TBTL

Member
2013-10-08 12:26 pm
Interesting. Is there an application for a long, long stroke driver with a very small surface?
I don't know. Long stroke drivers with a small cone areas are possible with many kinds of motor structures.

In my previous post I only wanted to emphasize that regular (voice coil in magnet gap) long stroke woofer motors either require (1) a large magnet structure or (2) having most of the coil sit outside of the magnet gap, where it does not contribute to the cone motion and only wastes power.


Alternative motor structures do not necessarily have this problem. Therefore there is a possibility that these can be cheaper to build or be more efficient.
 

academia50

Member
2013-01-16 2:52 pm
For a moment I thought I discovered the philosopher's stone, but no, the magnetic levitation trains do not use ferro fluid ....
I am intrigued because of this, perhaps it would escape from the magnetic space because the high travel speeds of the train are much higher than those of a VC within its magnetic space?

How I miss some controversies, hey , "just a boy" really knew !
 

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.............
In my previous post I only wanted to emphasize that regular (voice coil in magnet gap) long stroke woofer motors either require (1) a large magnet structure or (2) having most of the coil sit outside of the magnet gap, where it does not contribute to the cone motion and only wastes power.

......


You can increase the performance in low frequencies with long stroke and superimposed windings without the need of a magnet of many Gauss .....
There are "many roads to reach Rome", everything is a commitment ...
But even a high BL is not considered strictly necessary for deep bass, think of AR, have you seen the magnetic structure of your twoofers?

Greetings and have a good new year, friend ! :D
 
The servo-motor concept is cumbersome even it is one route to tremendous and very low emanations. Even if you can buy servo-motors with excellent linearity, still all the moving parts might make it worse than the Rice-Kellogg yo-yo system in current use.

With a ferro-fluid shock absorber, you'd have a "motor" of some kind and then motional feedback that would modulate the ferro-fluid in real time to get the cone placed exactly where it should be at each instant in time.

B.


How life changes us, you should have dedicated yourself to politics .....:D


Happy New Year for you too. :magnet:
 
Ben,

The Corvette and a number of other high end cars used Magnaride for their dampers. What they are doing is significantly simpler than what you are thinking of.

They are essentially conventional dampers, but they use ferrofluid so that they can fairly quickly modulate the viscosity of the fluid going through the shim stack in the damper. This is how they modulate the damper forces. They require power to do this of course, but they are not an active system in the sense that there is a forcing motor which allows the system to move into whatever position is required.

Even with a full active car suspension (linear motors) you can only fully control the HP response of the system. The LP response is a function of the tires sidewall stiffness and damping. Nothing in the car's suspension can affect that under any circumstances.

Bose has been advertising their linear motors for a long, long time. No one in the industry takes them seriously.
 
Off-topic

Are you using the term "active" in an idiosyncratic way?

"Finally, 2020 Corvette Stingray customers who opt for the Z51 package can also opt for the Magnetic Ride Control and Performance Traction Management (RPO code FE4). Essentially, Magnetic Ride Control uses accelerometers in the suspension to actively “read” the road and provide data to the ECU, which then adapts the damper settings on the fly for improved ride quality and performance."

So something "active" is happening. Just a matter of how big the feedback loop is.

Actually, as far as imaginative notions for drivers (in speakers), I wonder if ferro-fluid can have a bigger role than just for cooling even without being part of a feedback loop? An example would be Q adjustment which would sort of be called passive even if it only exists when the cone is moving. And of course, the mechanism need not be inside the conventional magnet motor circuit, where ferro-fluid is found today.
 
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Technically active means that the system uses power. In audio when people talk about an active versus passive crossover, with an active crossover there is an op-amp in a feedback loop. The op-amp uses power to form a servo. It can force the output voltage to be what it should be at different frequencies, regardless of the load. A passive crossover can't do that because it doesn't have a power source to do so.

The Magna Ride dampers are active, but they can't force the suspension to move anywhere in particular. The power is used to change the Q of the suspension, so that the energy stored in the springs and moving mass of the chassis will result in suspension velocities which are more desirable for the control setting.

That is the distinction I was trying to make.
 
It is not clear to me if the active system they refer to works on the shock absorber or on the spring.
A shock absorber inside has a check valve to make it difficult for the liquid to pass when the plunger moves up or down, and thus offer an opposition to the movement of the suspension spring, which is completely passive, because its movement causes it the mass of the moving vehicle that is altered by several forces, I will not list all of them here because it escapes my purpose.
It is very common for people not trained in the technical aspects of a car to confuse suspension with damping. They are two different things but they complement each other perfectly, for example in an MC Pherson system.
I am intrigued where and how an active vehicle stabilization system acts, I mean documentation, graphics, etc.

PD: I worked for many years at IKA RENAULT here and participated in the technical area as responsible for the warranty repairs of the vehicles.
I was the bad guy in the movie, you know, this flaw is covered by the guarantee or not covered) It was the times of the famous Torino car that had an honorable fourth place in Nürburgring. So I am passionate about the current conjunction of electronics and mechanics in modern cars.


El dia que el Torino argentino puso de rodillas a los autos mas importantes del mundo - Infobae


The statement is a bit superb, yes, I admit it, typical of us, the Argentines. But basically it is an inferiority complex, a topic for psychologists. I could also talk about that, I know everything ;):D!

"The day the Argentine Torino knelt the most important cars in the world."
 
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TBTL

Member
2013-10-08 12:26 pm
It is not clear to me if the active system they refer to works on the shock absorber or on the spring.
A shock absorber inside has a check valve to make it difficult for the liquid to pass when the plunger moves up or down, and thus offer an opposition to the movement of the suspension spring, which is completely passive, because its movement causes it the mass of the moving vehicle that is altered by several forces, I will not list all of them here because it escapes my purpose.
Active car suspension systems typically only modify the behaviour of the shock absorber / damper.

An exception is active suspension by Bose, which does have an actuator that is capable of moving the wheels up and down. It did not catch on, because it was heavy and consumed too much power. Last time I checked, their development efforts were sold to another company and used in active suspension for truck seats.
 
Car suspensions (academia50, in English usage "suspension" refers to the whole business) are a useful analogy to speakers (and vice versa) but can't be taken too far. Issues like size, shape, power demand, weight, and esp reaction time that matter to a car matter differently to a speaker.

I can think of only a few kinds of "motors" for drivers: voice coil, stepper servo motor, linear induction drive, plasma, electrostatic, crystal. Anything else in headphones or chair vibrators?

Ferro-fluid wouldn't be described as a motive power, I'd say.

Motional feedback can work with any of them.

Anything on the horizon?
 
At least on motorcycles, springs (as well as shocks) get a lot of attention with progressive winding, dual-rate, pre-loading, etc. A racing team might have their own winding machine to custom manufacture their springs for a specific race course.

On drivers, "spring" is a horrible joke since "the spring" is a hunk of rubber, accordion paper, and/or starched or treated fabric. Stupid springs, eh. Phenolic spiders were used originally.

Why don't we have precision metal springs in speakers?