I'm saying that John was simply refering to something different than what I was saying. What you said above is what I said and John disagreed explaining something that was not directed at my point. We all know the standard three rotating vector diagram for impedance near resonance. All three impedances are "significant" in this picture, but since the compliance and mass reactances are equal and opposite, they have no effect on the net result. John simply expressed that all three are present, which I never said otherwise.
A system’s response to any input is composed of two components; the forced response and the natural response. These are also referred to at the particular and complimentary parts of the solution. The system response is the sum of the two. The natural or complimentary part of the solution is the solution to the homogeneous system equation (no input or forcing function). The particular part is that which is determined by the forcing function. The transient response is that portion of the total response which decays to zero or a constant as time increases.
The response of a system to an pulse of finite width is the solution of the system to a step response of magnitude, M, at T = 0 minus the solution to a step of magnitude, -M, at T = Td, where Td is the duration of the pulse. You should be able to imagine that at T = Td the input returns to 0 (M + (-M) = 0). Also, you can imagine that at T= Td the system (cone) will have some acceleration, velocity and position which are not all mutually zero (rest state). There will be some energy stored in the mass, and some in the compliance. Thus, the decay of the cone motion will depend on the exchange of energy between the mass and compliance elements and how much energy is dissipated by the resistive element.
The response of a system to an pulse of finite width is the solution of the system to a step response of magnitude, M, at T = 0 minus the solution to a step of magnitude, -M, at T = Td, where Td is the duration of the pulse. You should be able to imagine that at T = Td the input returns to 0 (M + (-M) = 0). Also, you can imagine that at T= Td the system (cone) will have some acceleration, velocity and position which are not all mutually zero (rest state). There will be some energy stored in the mass, and some in the compliance. Thus, the decay of the cone motion will depend on the exchange of energy between the mass and compliance elements and how much energy is dissipated by the resistive element.
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Call it semantics or jargon. I would agree to resistance controled. Not to resistance dominated.
Dr. Geddes or John K.,
I'm not sure if this was previously covered. If we assume the system is isothermal (ambient, 293.15 K) previous to the forced input, the voice coil is thermally insulated from the rest of the system, and we know the mass and material of the voice coil, how can we determine the rate of internal energy generation (heating) of the voice coil for a particular input?
I'm not sure if this was previously covered. If we assume the system is isothermal (ambient, 293.15 K) previous to the forced input, the voice coil is thermally insulated from the rest of the system, and we know the mass and material of the voice coil, how can we determine the rate of internal energy generation (heating) of the voice coil for a particular input?
Thank you.
Do you think the statement below was trying to express "transients" in terms of onset of response?
My response was based on this statement. So unless we can both understand it in the same way. There seems not point in taking this further.
Your statement
Seems quite clear and doesn't need any reference to a prior statement to interprete. The compliance has nothing to do with "transients".
You were not able to appropriately answer the questions, so it's just pointless to discuss this further.
Here is an example I posted 2 years ago.
An externally hosted image should be here but it was not working when we last tested it.
This was a JX92S driver mounted on a Symmetric Air Friction Enclosure not really optimized. The enclosure was build about 20 years ago.
Yes. Lots of turns to create friction. There's an old patent on this technique, and a few articles in Popular Mechanics on it.
I believe viscous friction (ie resistance) increases with the square of velocity. As a result, wouldn't such an alignment be inherently non-linear?
I really have not done compliance measurements on boxed enclosures yet. So I really can't make an accurate judgement on that. The last SAFE enclosure made a few years ago never got a chance to run because the did not take into consideration wiring during assumbly process.🙁
I think the important point is the measured distortion for the same driver at the same excursion increases significantly when you put it in a small sealed enclosure. 2nd harmonic nearly doubles to 18% and 3rd harmonic nearly triples to 25%. The 7th and 8th go from under .1% to over 1%.
Now you may say that's inaudible but there is no question that the air spring contributes considerable distortion to real drivers in the real world so its effect is clearly not linear. It may be because of the extra power required but the result, not the reason, is the important thing for a system designer. Even if you don't notice the distortion as such, it will still help you locate the sub and that's a bad thing.
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Hi Dennis
The measurements and the theory don't jive. I believe the theory, I have my doubts about the measurements. Many other things could cause the measured results. "Theoretically" the measurements should not be precise enough to detect the small nonlinearity that the air presents (as the analysis clearly shows- 1% in 35%) and the air nonlinearity is purely asymmetrical so it should have no influence on the symetrical orders at all - like 3rd, 5th, etc. Sorry, those measurements just don't stand up to the credibility test.
Hi Earl,
Siegfried Linkwitz knows how to do measurements. 😉 These were done with the mic near the dustcap and he measured actual excursion so there's not much to go wrong. I'm pretty sure the difference in the theory and the measurements is the rather large power levels required to get the driver in the small box out to near Xmax at near Fs (well below Fb in the sealed box) -- sort of a variation on your dynamic compression.
Edit: I should add that his Thor is considered a very 'clean-sounding' sub so the distortion levels don't imply anything subjectively bad. And he has a pretty strong motive to not report the Thor's higher distortion if he thought he made an error in the measurements.
Siegfried Linkwitz knows how to do measurements. 😉 These were done with the mic near the dustcap and he measured actual excursion so there's not much to go wrong. I'm pretty sure the difference in the theory and the measurements is the rather large power levels required to get the driver in the small box out to near Xmax at near Fs (well below Fb in the sealed box) -- sort of a variation on your dynamic compression.
Edit: I should add that his Thor is considered a very 'clean-sounding' sub so the distortion levels don't imply anything subjectively bad. And he has a pretty strong motive to not report the Thor's higher distortion if he thought he made an error in the measurements.
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This is odd. The origins of theories were based on observation and measurement.🙄 Theory also change with new observations and measurements.
Then how do you explain the GROSS difference between theory and measurement. If I had taken that data, I would certainly be scratching my head and looking at the setup again. I don;t accept things when they disagree by this amount. Air nonlinearity is purely 2nd order. How can it affect the other orders? Explain that and maybe I'll listen.
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