Steve Eddy said:
It's not just the rest surface, it's the relative rigidity of the upper and lower surfaces and their detailed natures.
Let's do a minor reductio ad absurdum. Consider a square sheet of paper which is relatively thin and a base surface that's (relatively) infinitely massive and rigid. Put the cones on that surface pointy side down. And let's make the cones' diameter at the big end something large, say one-half the length of the sides of the sheet. Juggling furiously, we hold the cones and place the sheet of paper down on them. Now the paper sheet is contacted over a large proportion of its surface by the cones and has some constraint against moving. In fact, if the cones are made so that they'll stand up with their points down, the paper will lie pretty flat
Turn the cones over. Now the paper is contacted at 4 points only, and is not constrained for downward movement at all away from the points. It will sag.
Substitute a sheet of aluminum for the paper. I haven't run an FEA, but I'll bet a week's salary that the vibrational modes with the relatively low pressure, large area contact will be different (way different!) than the higher pressure, small area contact.
Second experiment: put some speakers on some stands. Place the speaker/stand on cones on a carpeted floor with the points up. Now do it with the points down. I'll bet there were some major rocking modes the first way, but not the second.
If memory serves, Stereophile magazine some years back actually did a vibration analysis on a speaker and stand, changing the interface between them (here, we're now talking about two relatively rigid surfaces). There were some easily measurable differences, and I think there were even data presented showing cone-up versus cone-down. I'll try to find that.
The other end of this is that, yes, most commercial applications of coupling/decoupling are based on superstition, hype, nonsense, and false claims of universality. And there (I think) we have common ground. I spike my speakers to the floor because I've got a concrete floor, not because I think that there's something "magic" or universal virtues to my spikes. If I had a loose wooden floor, I'd be looking at decoupling, not coupling, just so my turntable wouldn't skip and so that the resonant modes of my floor wouldn't be barking at me when excited by the speakers.
Isolation, Not Coupling Is The Go IMO
Hello Sy,
Umm, yep that is what I was saying about nodal points and tuning.
I find springs pretty much removes all of this dependency, and for the better.
Yep, with springs I find that my stands do not vibrate at all, but with hard mounts or cones they would ring like hell.
I agree that cones are largely a marketing exercise, and the 'diode' sales words are a big bending of the truth.
Due to the shape of cones, I expect that any internal sounds (vibrations) would be reflected assymetrically and give rise to a slight directional characteristic, but it is the thin sheet rocking/bending moments that you refer to as the causitive of sonic differences in my experience.
Eric / - You won't catch me shelling out good money for cones.
Hello Sy,
Umm, yep that is what I was saying about nodal points and tuning.
I find springs pretty much removes all of this dependency, and for the better.
Yep, with springs I find that my stands do not vibrate at all, but with hard mounts or cones they would ring like hell.
I agree that cones are largely a marketing exercise, and the 'diode' sales words are a big bending of the truth.
Due to the shape of cones, I expect that any internal sounds (vibrations) would be reflected assymetrically and give rise to a slight directional characteristic, but it is the thin sheet rocking/bending moments that you refer to as the causitive of sonic differences in my experience.
Eric / - You won't catch me shelling out good money for cones.
SY, I think we're talking at cross purposes here.
Sure, you can change the resonant modes of a vibrating panel depending on the contact area and type of material contacting it. I never said otherwise. That's not the issue here.
The issue is the cone itself.
The claim is that a cone couples energy from one body to another differently depending on whether the cone is pointy side up or pointy side down as well as differently compared to a cylinder.
That a force applied by one body to one end of the cone somehow results in some different force being applied to a second body at the other end of the cone. Which is where this whole bit about their being like a "mechanical diode" or a "funnel" or a "drain" comes in.
Whether one body is rigid and the other isn't or whether both bodies are the same is irrelevant. A given force is a given force regardless of its source.
~~~A force is a force. Of course of course. But who ever heard of a talking force? That is of course unless the force is the famous Jedi Ed.~~~
Sorry, couldn't resist.
Anyway, it's been my contention that for a given force applied by a given body to a coupler, that same force will effectively be applied to the second body whether the coupler is in the shape of a cone or a cylinder.
Frank has disagreed with this yet I haven't seen any evidence to the contrary.
What exactly is the point (no pun intended) to coupling to such a rigid mass as a concrete floor? What is it exactly that you're trying to do from a physical standpoint?
se
Sure, you can change the resonant modes of a vibrating panel depending on the contact area and type of material contacting it. I never said otherwise. That's not the issue here.
The issue is the cone itself.
The claim is that a cone couples energy from one body to another differently depending on whether the cone is pointy side up or pointy side down as well as differently compared to a cylinder.
That a force applied by one body to one end of the cone somehow results in some different force being applied to a second body at the other end of the cone. Which is where this whole bit about their being like a "mechanical diode" or a "funnel" or a "drain" comes in.
Whether one body is rigid and the other isn't or whether both bodies are the same is irrelevant. A given force is a given force regardless of its source.
~~~A force is a force. Of course of course. But who ever heard of a talking force? That is of course unless the force is the famous Jedi Ed.~~~
Sorry, couldn't resist.
Anyway, it's been my contention that for a given force applied by a given body to a coupler, that same force will effectively be applied to the second body whether the coupler is in the shape of a cone or a cylinder.
Frank has disagreed with this yet I haven't seen any evidence to the contrary.
What exactly is the point (no pun intended) to coupling to such a rigid mass as a concrete floor? What is it exactly that you're trying to do from a physical standpoint?
se
Re: SHIVA.
But you'd been speaking all along about the behavior of the CONE ITSELF. That the shape of the cone transmits energy differently versus a cylinder. That the CONE ITSELF behaves like a "funnel" or a "drain."
So are you saying now that a cone doesn't transmit energy from one body to another any differently than a cylinder?
se
fdegrove said:
But you'd been speaking all along about the behavior of the CONE ITSELF. That the shape of the cone transmits energy differently versus a cylinder. That the CONE ITSELF behaves like a "funnel" or a "drain."
So are you saying now that a cone doesn't transmit energy from one body to another any differently than a cylinder?
se
Steve Eddy said:
Yes, but the "given" foce is different when you change the resonant modes. The energy being transferred from one body to the other will be different if the forcing function is different, no?
In this case, coupling keeps the speakers from rocking with reaction forces. Coupling to a rigid surface may help reduce panel modes- I haven't done accelerometer tests, but the difference between spiking to the concrete versus having the stand just rest on the carpet is easily evident from just resting my hand on the top of the speaker box when I'm playing tunes loudly. Whether that's from rocking or panel modes or some combination, I don't know, but the net net is that the cabinets vibrate a good deal less with this setup.
Yeah, the diode stuff is kark, but far from the worst kark I've heard. My favorite is still the hockey pucks which are alleged to greatly affect room acoustics. I heard a demo of these magic pucks and I'm... unconvinced.
SY said:
Forcing function? What, we talking about atmospheric models now?
No, a given force is a given force. For example 2.4 Newtons could be a "given force." 0.6 Newtons could be a given force. Whatever.
You're not saying that a given amount of force is somehow different depending on what the source is are you? Like "tube watts" versus "solid state" watts?
That's why you put your woofers down at the bottom of the enclosure.
se
Ah, but we're not just talking about weight distribution. The force applied by the object on top of the cones has a weight, a constant force, but it also has an AC component as long as there's any vibrations present, whether through acoustic coupling from the air, taps by a finger, 60 Hz vibration from a transformer, jiggles from motors, whatever. THAT's what the isolation systems or coupling systems (depending on the tweak religion) are purported to get rid of. And THAT is what is different depending on the details of the contact to each surface. And THAT is why a cone will give a different result than a cylinder. Though I'll bet that it won't be any different than a cylinder with a little spike on the end.
As it happens, my woofers are indeed on the bottom. Roy Allison's papers were not lost on me.
As it happens, my woofers are indeed on the bottom. Roy Allison's papers were not lost on me.
SY said:
Sure. And I never said otherwise. I'm ignoring the "DC" component due to gravity. My point that a given force is a given force regardless of the source of the force or even whether the force is "AC" or "DC."
A Newton is a Newton is a Newton.
But THAT relates to the behavior of the OBJECT being coupled, NOT the coupler itself. And again, the claims being made relate to the behavior of THE COUPLER ITSELF.
~~~Fat bottom girls you make the rockin' world go 'round!~~~
se
But Allison only covers a small sunset of valid implementations of speakers. What about something like the Dunlavy's? Dunlavy was hardly a dogmatic tweaker extremist audiophile guru type.SY said:
(note; SY I'm not taking you to task, just commenting on the validity of different ways of doing it)
Sure, I've done it more than one way- after all, I spent a few years working with the designer of the Nova speakers and the Dynaudio Consequence. But the woofer-on-the-floor Allison approach works best for the particular design I'm using at the moment. And it makes a much better package for me, less susceptable to tip-over- I have a 2 year old and 5 cats.
Well, Steve, I can't in my own head separate these factors as easily as you can. I'm looking at object-coupler-base as a system. I don't argue that there's something magic about cones as a shape, merely that the behavior of the system as a whole is affected by the cone direction, if that's the coupler chosen.
everything I was afraid to ask before
Hi
Let`s asume that we have an air floating base platform and CDP with 3 cone legs siting on it (flat side of cone on CDP side). The only way to get rid of vibrations by the physics stand will bee I presume throught vib. energy to heat transformation (partly through CDP-air, small amount-coupler-air, mostly-base-air). I supouse that the main goal in audio would be to achive wery fast vibration transfer from (out of) CDP through coupler (cone, spring, cilinder, condom, Pirreli tyre...) in to the base with ability of fast enrgy to heat transfer, and certanly to prevent (as much as possibile) vibrations runing up and down through the coupler. So the coupler in ideal world should work as a diode. Does the cone, springs etc. do that? No idea-I don`t know anything about phisics. But I`d like to know. So here is a few questions. I`d aprishiate any answers.
1. Does the shape of coupler determine the spid (not amount) of vibrations transfer from object to base
2. Does the spid of transfer and amount of transfered vibrations , depend on surface area betven object and decoupler ( lt say 0,5 squere inch or 2 squere inch) and how does it act in boath cases if yes
3. Is it the frequency of vibrations runing from obj - coupl - base, changed going through the coupler? In wich way and depending on what?
rgds
Marijan
Hi
Let`s asume that we have an air floating base platform and CDP with 3 cone legs siting on it (flat side of cone on CDP side). The only way to get rid of vibrations by the physics stand will bee I presume throught vib. energy to heat transformation (partly through CDP-air, small amount-coupler-air, mostly-base-air). I supouse that the main goal in audio would be to achive wery fast vibration transfer from (out of) CDP through coupler (cone, spring, cilinder, condom, Pirreli tyre...) in to the base with ability of fast enrgy to heat transfer, and certanly to prevent (as much as possibile) vibrations runing up and down through the coupler. So the coupler in ideal world should work as a diode. Does the cone, springs etc. do that? No idea-I don`t know anything about phisics. But I`d like to know. So here is a few questions. I`d aprishiate any answers.
1. Does the shape of coupler determine the spid (not amount) of vibrations transfer from object to base
2. Does the spid of transfer and amount of transfered vibrations , depend on surface area betven object and decoupler ( lt say 0,5 squere inch or 2 squere inch) and how does it act in boath cases if yes
3. Is it the frequency of vibrations runing from obj - coupl - base, changed going through the coupler? In wich way and depending on what?
rgds
Marijan
Hi Marijan
The high-end audio world is no more comrehensible to a physicist than a mosque to an atheist. Understanding of mechanical principles or even minimising of vibrations is no guarantee for pleasing sound. Your questions are however quite simple.
1. The shape of the coupler will not change the speed which is only determined by the material.
2. Again the speed of propagation only depends on the material while the amplitude will depend largely on the similarity/dissimilarity of the materials and whether you get reflection/refraction/absorbtion in the contact area.
3. The coupler cannot change the frequency.
This whole issue is of course very complicated as in the normal situation where a component is coupled to a surface, this surface may inject more air/structure borne vibrations back to the component. 'Draining' vibrations away is indeed very difficult. I am very suspicious of hifi stands where a component resides on top of a large vibrating surface where indeed you may have a bigger task stopping vibrations entering the component from the stand than draining vibrations away from the component.
Springs, rollerblocks, airbladders will all work well at isolating some frequencies, but not others. All stand and shelf materials will generally add their own spectrum of vibrations and the end result will be very difficult to predict.
Some materials are certainly worse for support than others. I have severe intolerance towards steel/glass (can you spell MANA?), MDF and generally very heavy structures. Extremely light and rigid has worked well with my ears and so has the absense of shelfs. If you absolutely need to use massive steel racks, some kind of decouping (air bladders, rollerballs) seems to work fine. Nothing, however beats the light/rigid/shelfless concept in regards of subjective dynamics and bass quality.
regards
peter
The high-end audio world is no more comrehensible to a physicist than a mosque to an atheist. Understanding of mechanical principles or even minimising of vibrations is no guarantee for pleasing sound. Your questions are however quite simple.
1. The shape of the coupler will not change the speed which is only determined by the material.
2. Again the speed of propagation only depends on the material while the amplitude will depend largely on the similarity/dissimilarity of the materials and whether you get reflection/refraction/absorbtion in the contact area.
3. The coupler cannot change the frequency.
This whole issue is of course very complicated as in the normal situation where a component is coupled to a surface, this surface may inject more air/structure borne vibrations back to the component. 'Draining' vibrations away is indeed very difficult. I am very suspicious of hifi stands where a component resides on top of a large vibrating surface where indeed you may have a bigger task stopping vibrations entering the component from the stand than draining vibrations away from the component.
Springs, rollerblocks, airbladders will all work well at isolating some frequencies, but not others. All stand and shelf materials will generally add their own spectrum of vibrations and the end result will be very difficult to predict.
Some materials are certainly worse for support than others. I have severe intolerance towards steel/glass (can you spell MANA?), MDF and generally very heavy structures. Extremely light and rigid has worked well with my ears and so has the absense of shelfs. If you absolutely need to use massive steel racks, some kind of decouping (air bladders, rollerballs) seems to work fine. Nothing, however beats the light/rigid/shelfless concept in regards of subjective dynamics and bass quality.
regards
peter
Peter,
thaks for replly. So you say if I understand you corectly, draining of vibrations will be equaly fast from object to base no mather what shape (cone, cilinder, ball, ....) of the coupler I use, presuming there is identical material and (maybe?) similar mass of coupleing elements, and frequency of vibration will be the same on input and output point of the coupler.
What would you recomand as extremly light and rigid material for given purpouse? Acryl,.......?
regards
Marijan
thaks for replly. So you say if I understand you corectly, draining of vibrations will be equaly fast from object to base no mather what shape (cone, cilinder, ball, ....) of the coupler I use, presuming there is identical material and (maybe?) similar mass of coupleing elements, and frequency of vibration will be the same on input and output point of the coupler.
What would you recomand as extremly light and rigid material for given purpouse? Acryl,.......?
regards
Marijan
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