Is the ideal restoring force applied by the spring on the moving assembly:
1) constant => F(restoring) = c for all x, c is a constant
2) linear => F(restoring) = kx for all x
3) parabolic => F(restoring) = kx^2 for all x (might be another coefficient in there)
I think Klippel covered this in one of his papers but either I can't find it or it disappeared off the Internet.
1) constant => F(restoring) = c for all x, c is a constant
2) linear => F(restoring) = kx for all x
3) parabolic => F(restoring) = kx^2 for all x (might be another coefficient in there)
I think Klippel covered this in one of his papers but either I can't find it or it disappeared off the Internet.
ideally, the mechanical compliance of the moving system or (1/stiffness) is constant for each position of the cone. So answer (1). This is also the assumption in the most simple electromechanical models.
Unfortunately, this is not the case for real world drivers as can be seen in Klippel measurments of Cms kindly borrowd from npdang on diyma. The measured Cms values can be reasonably approximated by an quadratic fit, so (3).
Unfortunately, this is not the case for real world drivers as can be seen in Klippel measurments of Cms kindly borrowd from npdang on diyma. The measured Cms values can be reasonably approximated by an quadratic fit, so (3).
Hi,
I'm sorry but 1) is a non-starter and not the definition of a spring.
2) Is of course a classic ideal spring, theoretically zero distortion.
3) you can reword to as non-linear, not necessarily parabobic.
Practically all suspensions are 3).
The air in box is very nearly 2 except at very high compression.
/sreten.
I'm sorry but 1) is a non-starter and not the definition of a spring.
2) Is of course a classic ideal spring, theoretically zero distortion.
3) you can reword to as non-linear, not necessarily parabobic.
Practically all suspensions are 3).
The air in box is very nearly 2 except at very high compression.
/sreten.A spring need not be linear (follow Hooke's Law), so I don't see how a constant force means that the device is not a spring.sreten said:Hi,
I'm sorry but 1) is a non-starter and not the definition of a spring.
2) Is of course a classic ideal spring, theoretically zero distortion.
3) you can reword to as non-linear, not necessarily parabobic.
Practically all suspensions are 3).
The air in box is very nearly 2 except at very high compression.
2) - is F=kx really the ideal for zero distortion? This conflicts with what LaMa said.
Just one question: If a linear restoring force were the way to go, how would you want it to behave within a loudspeaker driver (which should be able to move in two directions) ? How about the situation at zero displacement ? Equal restoring force in two directions at once ?
A spring following Hooke's law as closely as possible is still the way to go. There are possibilities to implement progressive restoring force at high excursions in order to achieve mechanical protection at high excursions though.
Regards
Charles
A spring following Hooke's law as closely as possible is still the way to go. There are possibilities to implement progressive restoring force at high excursions in order to achieve mechanical protection at high excursions though.
Regards
Charles
OK fine. But how would you implement something that shows a constant restoring force as soon as even the slightest displacement is reached ? And when exactly is "slight" reached ?
Such a function would be very discontinuous and unnatural and trying to achieve it in reality is therefore futile.
A restoring force according to Hooke's law is still the way to go.
Regards
Charles
Such a function would be very discontinuous and unnatural and trying to achieve it in reality is therefore futile.
A restoring force according to Hooke's law is still the way to go.
Regards
Charles
Mayvbe I am overlooking things - most probable I DO - but isn't actually the truly ideal restoring force NULL ? At least for a driver with perfectly linear motor ?
As far as I can see, the role of the spider and surround (and their inherent compliance) is purely to ensure that the diaphragm stays in place - theoretically, in imponderability, you could build a speaker without spider and surround.
I am aware that this would actually lead to the conclusion that very low Qms drivers are the best - which might be simply not true.
At least I do not see why an ideal kx spring would be theoretically better - does this in any way fit any aspects of the driver's motor ? Sure, a non-linear spring is obviously worse (or it mighyt be better if it "complements" the non-linearity of the driver motor itself?)
just wondering.
As far as I can see, the role of the spider and surround (and their inherent compliance) is purely to ensure that the diaphragm stays in place - theoretically, in imponderability, you could build a speaker without spider and surround.
I am aware that this would actually lead to the conclusion that very low Qms drivers are the best - which might be simply not true.
At least I do not see why an ideal kx spring would be theoretically better - does this in any way fit any aspects of the driver's motor ? Sure, a non-linear spring is obviously worse (or it mighyt be better if it "complements" the non-linearity of the driver motor itself?)
just wondering.
It may help to understand the dynamics of a driver. First the ideal driver would have no spring and no damping, with as little moving mass as possible. Such a driver would response linearly to the force applied, according to Newton’s' Law. However, there is no means of assuring that the driver would return to the rest (or starting) position once the force is removed, or even stop moving for that matter. Again, Newton's Law states that a body in motion remains in motion unless acted upon be an external force. The "suspension spring" is added to the diver to supply that external force. It assures that the driver will return to the rest position when the forces is removed. Ideally this would be a linear spring IF the driver motion is to remain a linear function of the input force. However, real driver suspension is highly nonlinear at the extremes (beyond Xmax). This is necessary to prevent the excursion of the driver from exceeding some mechanical limit which would result in physical damage. Finally damping is added to the system because without damping the driver would, in theory, never stop oscillating at its resonant frequency once started.
It is also of interest to understand where the different aspects of the driver mass, spring and damping with frequency. At low frequency, below resonance, the suspension spring is the dominant factor in determining driver motion. At resonance, the mass, spring and damping all play equal rolls. Above resonance the driver motion is dominated by the moving mass unless the driver excursion is pushed to the excursion limits where the suspension spring becomes very stiff.
It is also of interest to understand where the different aspects of the driver mass, spring and damping with frequency. At low frequency, below resonance, the suspension spring is the dominant factor in determining driver motion. At resonance, the mass, spring and damping all play equal rolls. Above resonance the driver motion is dominated by the moving mass unless the driver excursion is pushed to the excursion limits where the suspension spring becomes very stiff.
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