OK, back to this impulse response thing. I've done a lot of measurements recently so I can understand cone damping and stiffness.
Driver B's polar response now looks like this:
started from this:
The same driver's overlaid impulse responses looks like this:
From this:
AVG response is now this:
but started out looking like this:
So it's quite easy to see that the tail has been chopped. That would say to me that we have less stored energy. Please correct me if I'm wrong or explain if it's not that simple.
Now the other thing I see it a reduced amplitude of the initial spike. Does this correlate in the polar graph/AVG graph to the reduced efficiency below the break up?
Anything else I should see in this?
Thanks,
Dan
Driver B's polar response now looks like this:
started from this:
The same driver's overlaid impulse responses looks like this:
From this:
AVG response is now this:
but started out looking like this:
So it's quite easy to see that the tail has been chopped. That would say to me that we have less stored energy. Please correct me if I'm wrong or explain if it's not that simple.
Now the other thing I see it a reduced amplitude of the initial spike. Does this correlate in the polar graph/AVG graph to the reduced efficiency below the break up?
Anything else I should see in this?
Thanks,
Dan
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Cone stiffening.
Here's the polar response of another of these junk drivers:
I used a paper stiffening compound on the cone cone and got this:
Impulse went from this:
to this:
Nothing was added to the surround. Cool thing here is that we increased the frequency where the break up starts, but what do we see in the impulse? The second positive deflection and fourth around 0.5 msec have grown and become more uniform. Can anyone explain what's going on here? The best I can make of it is that we have more stored energy early on, but it dissipates faster. Correct? Is there some more I should see in here? Does it also show less high frequency stored energy demonstrated by the more uniformity? I'm just guessing, but curious.
Thanks again,
Dan
Here's the polar response of another of these junk drivers:
I used a paper stiffening compound on the cone cone and got this:
Impulse went from this:
to this:
Nothing was added to the surround. Cool thing here is that we increased the frequency where the break up starts, but what do we see in the impulse? The second positive deflection and fourth around 0.5 msec have grown and become more uniform. Can anyone explain what's going on here? The best I can make of it is that we have more stored energy early on, but it dissipates faster. Correct? Is there some more I should see in here? Does it also show less high frequency stored energy demonstrated by the more uniformity? I'm just guessing, but curious.
Thanks again,
Dan
Dynamic mass vs frequency is changing with the added compound. Breakup mode becomes more concentrated as the cone gets stiffer. Probably the interaction with the surround has changed as well.
Dan, yes reducing the "ring-out" can be called "strored energy, I guess, and it ius a good thing to get rid of any of this ringing. I just object to the term "stored energy" because its not necessarily correct. It could just be non-minimum phase and there is no "stored energy".
The steepness of the initial impulse corresp[onds more to the HF response. Total response depends on total impulse, not the front or the end.
"Dynamic mass"? Thats a new one. I thought that "mass" was a static quantity. How does it change "dynamicaly".
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Thanks Soongsc!
Also it would be good to hear from Bud P. as I believe he has a patented processes dealing with the same phenomenon. Or from maybe Planet10 as he has a ton of experience with FRers and cone damping techniques. It would be great to see how their data compares as I've seen little of it from EnAble or any other technique. The only stuff I have seen was from Soongsc.
Dan
Also it would be good to hear from Bud P. as I believe he has a patented processes dealing with the same phenomenon. Or from maybe Planet10 as he has a ton of experience with FRers and cone damping techniques. It would be great to see how their data compares as I've seen little of it from EnAble or any other technique. The only stuff I have seen was from Soongsc.
Dan
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That's educational. Thanks! Now I've got more to think about, but a better insight into what to think.
I think what Soongsc was saying is that the cone is behaving more like a piston higher into the frequency response that the softer cone. That's how I took it, but that was what I already thought so my brain filter was probably distorting his meaning to some degree.
Dan
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"delayed energy" would certainly be more correct since that is pretty much what happens. Take a flat spectrum for example and apply an all-pass filter to it. The spectrum stays flat - no change in energy, but it smears the impulse response adding a tail. The energy in the tails has been delayed by the all pass filter. SO I suppose you could say that it was "temporarily stored" and then transmitted, but delayed just sounds more accurate to me.
Quite interestingly, I used the term "effective mass" in a private discussion, the other person was unfamiliar with that term, when I used "dynamic mass" he knew what I was talking about. Basically, this happens when pushing a flexible object, before the whole object starts to accelerate as a rigid body, the reactive force is such that it's like a lower mass. "Effective mass" is a term also used to describe tone arm characteristics as a property for selecting cartrige compliance.
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I have a different process patent in China and Taiwan. Some effects I have shown in the EnABL thread. Simulation using Ansys was conducted to understand the modal changes, and later tested using the Klippel scanner. Quite incidentally, I asked about it right before it's first announcement in San Fransisco (if I remember correctly). If you want to know more about cone vibration, Ted Jordan had some articles on this subject in Wireless World back in the 80's.
Mark over here also has a good understanding on cone vibration.
http://www.diyaudio.com/forums/full-range/28355-markmcks-tang-band-mods.html
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Help me understand.
When the voice coil applies a force to the cone, 100% of the cone's mass reacts against the implied force. Am I not correct? There is also the suspension's resistance, but I am going to ignore that for the moment.
So how can the reactive mass be lower than the total moving cone mass?
Never mind, I think that I see what you are saying.
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Mass is mass and it never changes. But if the structure is flexible then it behaves "differently" that a rigid one. Its "reactance" is a combination of its stiffness and its mass, whereas in the rigid case its reactance is simply just the mass. To call this "dynamic mass" is not precisely correct, whereas "dynamic reactance" would be. Initially this reactance will be almost purely compliant and then it becomes mass like as the object accelerates and the reactance changes, but the mass and compliance never change. There is no such thing as "dynamic mass", albeit there are comliance effects which can be called "dynamic".
Dynamic Mass? How about above and below the frequency of cone modes or breakup. The mass being driven is less above those frequencies because of cone flexing with the energy not reaching the surround in the same way. The "apparent mass" as reflected through the voice coil will be lower. Apparent mass can change with frequency.
I think the actual terms for mass are either invariant mass or reactive mass. There is no such thing a dynamic mass.
In relativistic domains, it is referred to as relativistic mass, but that does not apply here. I can assure you that no transient response gets near that. 🙂
I can only say that people with different engineering background communicate some terms differently. This will occur more often on an international scale. The important thing is to understand what is happening to avoid miscommunication. Whenever reactive force is converted to equivalent mass, the purpose is to use the mass term in computations which is very adequate for specific purposes. Method as such is commonly use, such as T/S parameters.
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This was just a suggestion to point out apparent mass changes with frequency. What the effect is called is another question. Reactive mass? Is this mass with potential energy stored and released? That would be some form of oscillator or resonator and not simply mass. A spring mass damper system if you will.
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Note that some springs will oscillate with not additional mass attached. Just think about that. How would one model it in engineering terms?😉
As a distributed mass/spring system, just like air. That is unless you can somehow make a spring that has no mass. That would be very useful!
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