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 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.
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
jan didden
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.
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.
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.
Last edited:
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
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
Last edited:
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.
That's interesting, because Magnet size and Bl have nothing to do with resonant frequency.
You know, there are very convenient sets of equations that let you figure all of this out on your own. Start here:
Thiele/Small - Wikipedia, the free encyclopedia
-Charlie
Thiele/Small - Wikipedia, the free encyclopedia
-Charlie
Yeah well that's why I like this forum. That never was obvious to me but you are right. I always assumed the size of the magnet was like the spring constant in the mass-spring simulations. Big magnet = stiff spring = higher natural resonant frequency.
Got a couple if issues that are not related but being lumped together.
First is the driver system free air resonance, Fs. This is a result of the total moving mass and the compliance of the suspension, air etc. It has nothing to do with light or heavy cone, but the total of the system. It has nothing to do with the rigidity of the cone. MMs in T/S speak. It's Q is again related to the suspension, not the cone stiffness. Think of a weight on a spring with a damper on it.
The cone resonance is what controls breakup modes. This is not related to free air resonance. It is related to the stiffness of the material and it's shape. Vary light material can have low resonance, think of a piece of silk. Think of a big steel plate that can ring like a bell but weigh a ton. Stiffness and shape, not mass.
The stiffer something is, the higher the resonant frequency. You can make something very light, buy floppy and have very low resonance. You can make something weigh a ton, and ring like a bell at high frequency.
First is the driver system free air resonance, Fs. This is a result of the total moving mass and the compliance of the suspension, air etc. It has nothing to do with light or heavy cone, but the total of the system. It has nothing to do with the rigidity of the cone. MMs in T/S speak. It's Q is again related to the suspension, not the cone stiffness. Think of a weight on a spring with a damper on it.
The cone resonance is what controls breakup modes. This is not related to free air resonance. It is related to the stiffness of the material and it's shape. Vary light material can have low resonance, think of a piece of silk. Think of a big steel plate that can ring like a bell but weigh a ton. Stiffness and shape, not mass.
The stiffer something is, the higher the resonant frequency. You can make something very light, buy floppy and have very low resonance. You can make something weigh a ton, and ring like a bell at high frequency.
I didn't even know there was a thing such as cone resonance. I don't recall seeing it in Dickason's Loudspeaker design cookbook.
I have this idea that if one were to make a cone like a shaker berry basket but use aluminium for the staves(radial part here) and aerolam for the weavers(concentric part here) you would have a speaker with the pistonic qualities of aluminium with out the ringing. It would weigh a little heavier than air hence be near the 42 acoustic ohms/cm2. thanks
I have this idea that if one were to make a cone like a shaker berry basket but use aluminium for the staves(radial part here) and aerolam for the weavers(concentric part here) you would have a speaker with the pistonic qualities of aluminium with out the ringing. It would weigh a little heavier than air hence be near the 42 acoustic ohms/cm2. thanks
Though as Sreten pointed out, a smaller magnet will be needed to get the same Qts.
A lighter cone would be more efficient, as its easier to accelerate than a heavier cone.
Hi,
All cones resonate due to the fact they have a speed for the propogation of
sound, giving a wavelength to the edge and they enter breakup mode for
wavelength shorter than this. There are also lesser modes regarding waves
travelling circularly around the cone. Curved cones are stiffer around the
the cone at the cost of radial stiffness. Break up can be damped, softer
cones, or quite high Q, typical metal cones.
The only diaphragms that couple efficiently to air are electrostatics.
You can't make a typical moving coil driver that does. Well you can
with an near infinitely stiff cone and thus next to no weight and also
assume the coil weighs next to nothing, both pointless assumptions.
For a real driver with real coils the coil mass represents a limit
it is near pointless making the cone any lighter, if you could.
I've pondered 3D structures for cones quite a lot, but they are
a lot more difficult to make than sandwich cones, expensive.
rgds, sreten.
All cones resonate due to the fact they have a speed for the propogation of
sound, giving a wavelength to the edge and they enter breakup mode for
wavelength shorter than this. There are also lesser modes regarding waves
travelling circularly around the cone. Curved cones are stiffer around the
the cone at the cost of radial stiffness. Break up can be damped, softer
cones, or quite high Q, typical metal cones.
The only diaphragms that couple efficiently to air are electrostatics.
You can't make a typical moving coil driver that does. Well you can
with an near infinitely stiff cone and thus next to no weight and also
assume the coil weighs next to nothing, both pointless assumptions.
For a real driver with real coils the coil mass represents a limit
it is near pointless making the cone any lighter, if you could.
I've pondered 3D structures for cones quite a lot, but they are
a lot more difficult to make than sandwich cones, expensive.
rgds, sreten.
Cone breakup modes are one of the toughest things to deal with, both from a manufacture and from us users. They are talked about in a lot of places. Zaph, Linkwitz etc. They can be a problem, or can be worked around. That is part of the fun of design. As an example, the Fostex 125 is a light paper full range but has horrible breakup at 6K making it suitable for a midrange crossed over at about 2K. Yet my Seas metal tweeter breakup at 26K seems to not cause me any problems. My Dayton RS metal mid-base drivers caused me to use a quite steep crossover to get good results. Seas just changed the profile of some of their cones. This pushed the breakup resonances up about 2K making them much easier to use. The AES anthologies on loudspeakers has many papers on this. You will soon learn EVERYTHING has resonances that can cause problems. Port tubes, binding jack plates, braces.
Speakers are all about vibration. Good and bad.
Sreten makes a good point as usual: Even in a big honking woofer, the vc, former, glue, half the suspension, spyder, and everything else dwarfs the cone mass. Makes you wonder what some of the OEM's are thinking! I still think the true aerogell or AKA liquid smoke, has the possibility for a great tweeter dome.
Speakers are all about vibration. Good and bad.
Sreten makes a good point as usual: Even in a big honking woofer, the vc, former, glue, half the suspension, spyder, and everything else dwarfs the cone mass. Makes you wonder what some of the OEM's are thinking! I still think the true aerogell or AKA liquid smoke, has the possibility for a great tweeter dome.
10 years ago at Madisound forum they were talking about the newly synthesized spider web material that was near massless but exceedingly strong like a real spider's web and that a spider speaker was not far off in the works. Cones stills seem to be made of carbon fiber. The Magico cones are touted as nanotech but if you read their literature it's just a coating. They are still essentially a carbon fiber sandwich. I thought a near massless cone matching the 42 acoustic ohms of the air was the holy grail. I thought I had a good idea with my berry basket cone of beryllium staves and aerolam weavers. Both are Nasa materials. Graphene produced there in Manchester might be the next generation of speakers. I've watched them make it on YOutube. Not a really difficult process to make like aerogel. Thanks.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.