Do lighter cones of a given size dampen and settle quicker?

[asberrys]

Do lighter cones of a given size settle quicker? As the acoustical impedence goes up with frequency is their an optimum frequency for a given cone size and weight at which it is best self dampened by the air? Is there a formula for this?
A cone that settles quicker means less distortion probably as it nears its Xmax relative to other same sized cones that "ring" a little before the next excursion correct? Thanks in advance.

[weltersys]

Originally Posted by asberrys

Do lighter cones of a given size settle quicker? As the acoustical impedence goes up with frequency is their an optimum frequency for a given cone size and weight at which it is best self dampened by the air? Is there a formula for this?
A cone that settles quicker means less distortion probably as it nears its Xmax relative to other same sized cones that "ring" a little before the next excursion correct? Thanks in advance.

A lighter cone requires less Bl (magnetic strength) to dampen it's movement than a heavier cone.
FS, the resonant frequency of the cone is dependent on cone weight, suspension compliance and Bl.
There is no one "optimum frequency", speakers are designed to cover a range of frequencies.
A lighter cone generally has more distortion when driven near Xmax than a heavier, stiffer cone.

[jan.didden]

The major source of distortion, especially at higher frequencies, is not cone 'overshoot' or something like that. It is cone breakup; the cone no longer acts as a homogeneous piston but starts to flex and have all kinds of local partial vibrations. So a stiffer cone that maintains pistonic behaviour has, generally speaking, less distortion.

jan didden

[planet10]

Given the complex interactions of the parts of a driver, the answer is: "ot depends on everything else". Motor, material, suspension, VC, shape, glues used...

dave

[asberrys]

Okay well thanks for the answerers. Let me further specify that the lighter cone is perfectly pistonic throughout its range. If another heavier cone speaker with the same resonant frequency is also perfectly pistonic in the same range what are the advantages of the lighter cone? it is more efficient? will it dampen and settle better? Yeah I know the lighter cone will require a smaller magnet and Bl product to have the same resonant frequency as the heavier cone. thanks.

[thoriated]

My feeling is that a speaker with overall higher conversion efficiency (which goes with light cones for direct radiators) tends to have slightly less leftover energy to convert to high Q resonances, and the energy that is converted to unintended resonances tends to be lower in level relative to the intentional output.

An example might be two drivers of the same size with similar magnetic assemblies but one with a light cone and suspension having high conversion efficiency and one with a heavy cone and suspension with a low to moderate conversion efficiency might excite similar amounts of *mechanically* (as opposed to acoustically) coupled resonances throughout the enclosure, but the high conversion efficiency driver would have that much higher a direct output than the other which would mask those resonances more effectively. Plus, very high conversion efficiency direct radiators (assuming they have smooth responses) can translate 5-10% of their electrical energy into sound which would not tend to support resonances in the driver itself with Q's much higher than 3 -5 within their passband at least, so less in the way of droning type resonances would be expected from that mechanism.

[mattlong8]

momentum = mass x velocity*.

The more mass a moving body has, the more difficult it is to slow down *in it's direction of travel.
That being said, the real answer is much more complex as it varies with material, cabinet design and the driving signal.
[edit] As stated rather well above =).


-Matt Long
SF, CA

[Inductor]

OP. You probably will look at a mix of the two. You don't want the reflected sound waves from the inside of the cabinet at certain (mid-high) frequencies (in a very light cone).

[sreten]

Originally Posted by asberrys

Yeah I know the lighter cone will require a smaller magnet and Bl product
to have the same resonant frequency as the heavier cone. thanks.

Hi,

Nope. It must have a higher Vas, less suspension stiffness for the same Fs.

It would need less magnet and BL for the same Qts at Fs. It would be more
efficient but as Vas has gone up need a bigger box for the same bass extension.

Cone mass is very much to due with the bass extension vs. efficiency
vs. box size tradeoffs for the driver, infinitely stiff or not doesn't matter.

rgds, sreten.

[Ron E]

Originally Posted by asberrys

Yeah I know the lighter cone will require a smaller magnet and Bl product to have the same resonant frequency as the heavier cone. thanks.

That's interesting, because Magnet size and Bl have nothing to do with resonant frequency.