This is the core of the failure - an EE is usually not qualified to calculate shock waves, this is a job for an ME trained in Gas Dynamics.
A competent project manager ensures that a knowledgeable team performs the task.
We get roughly 1500 scientific type people here on a yearly basis. Because I designed the entire machine non AC power wiring to NEC, many high sensitivity instruments will be susceptible to ground loop noise. NEC is rabid when it comes to bonding all equipment, and it cares not what kind of ground loops are formed. So I am called in to troubleshoot the problems.
While some of the scientific types will have a very high level of self confidence (and rightly so), none have the attitude on display here. Even if it takes a few hours to fix, they are very nice.
Over the last five years, perhaps 5 thousand, granted that is a small sample size..
Jn
Or at least someone who knew what a chronograph is.
And I thought you could work out muzzle velocity with math to a fairly accurate representation of reality?
I was not listening while the Hv was being changed. yes, it should sound different but I never listened to it i any other condition than flat response.
So, I never heard it affecting the sound.
THx-RNMarsh
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Ditto. I have never heard this type of talk and dialog anywhere, ever. I know people who have just make a negative biased comment about a person on the job and was severely reprimanded. Nothing that comes close to what people feel they can talk to others here. Such talk would not be tolerated anywhere a second time. And, moderators do nothing most of the time. Thus enabling.
THx-RNMarsh
Good people managers of technical personnel are hard to find. Either the manager is chosen from a highly technical personnel pool. In which case you loose a very good tech person and gain a poor manager. OR, the other, you have a very good technical manager but poor in managing people.
is there a person good in both technical and managing people? yes and I worked for a few. But not many are good at both.
THx-RNMarsh
But still just an opinion, isn't it?
I try to avoid that; as I've noticed that you in the past in your responses quite often confused facts and opinions (means that you've denoted facts as opinion) I have to asked if you could quote some examples?
Mythomaniac. When a poor little technician invents a life of nobel prize.
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Not the kind of thing I meant at all, but never mind, it's the sort of post I've come to expect from you, and part of the problem I was alluding to.
That's good to hear, they behave in the real world, although who knows how they behave on social media sites?
I don't get the hatred for those who understand something on a basic level.
Here, the only way for scientists to get promotions is to publish. Specific quantities of papers per year.
I can see that as a reason to favor quantity over quality.
The engineering disciplines here on the other hand, tend to favor quality and exceptional performance over writing papers.
A scientist or physicist here who is an exceptional performer doing great things that nobody else can, will get nowhere if they don't have the number of papers published to satisfy requirements.
I do not envy them. The system seems geared towards having scientists with no practical experience, and engineers with no high level theory.
And then there is me.. sigh...when asked to check all the boxes on the abilities questionnaire paper that I was good at, I said...what paper???😕
jn
Of course it could be, but have you any factual evidence for your claim (you know wrt the "bubbles")?
But is it really that?
I understood it more as a general critic of the system favouring the "publish or perish" mantra, that one is forced to follow to get additional financial support and to get the promotion within the university; it seems to lead to kind of inflation of publications resulting from an experiment or a series of experiments.
Of course must not be the same in all fields.
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Thank you for your mature reaction, so let's go on with the subject instead fighting each other and let's not forget giving Peter Walker full honor for having invented such a beautiful machine more than 40 years ago.
You are quite positive about the Streng paper, supplied by Jakob, so let's go in some detail.
Streng describes the redistribution of charge on the membrane, depending on level (=membrane deflection) and frequency.
However, as Streng describes, this has mainly its effect at LF and be aware that he does not vary the HV.
This effect is also visible in the speakers impedance that is clearly level dependent.
Unfortunately I don't know where to find these old measurements anymore, but the effect is well known since the introduction in 1981.
In our case we are discussing the possible changing in HF BW when changing HV.
My opinion was and stil is, that changing HV has its effect gain but not on HF BW.
The electric field will change when changing HV so will the charge on the membrane and with it the resulting force on the membrane when a differential voltage is applied.
In no way a frequency dependant component is part of the equation above the resonance frequency (ca 50Hz for the ESL63).
But what is also visible in the impedance curve is another peak at 20Khz.
Assuming that at 20kHz mainly the rings are radiating, and assuming a capacity of those rings of 0.75nF, there must be some 85mH series inductance be part of the equation.
Now the question may be, what is causing this series inductance and is it dependant on HV ??
Could this be the secondary of the Audio transformer or is it part of the complex filter to flatten HF to 20Khz ?
Hans
That has always been my objective.
As I said, he stated quite clearly in his last sentence a need to worry about the hv level, but that he did not specifically point it out as part of the analysis.
He also demonstrated by actual test, time dependent behavior, bursts which vary in amplitude, getting stronger over the time of the burst.
His analysis shows a clear lateral dependence of charge movement with excitation, I do not recall if he evaluated that vs frequency.
You and I agree that the system on first principals (being one dimensional in analysis), should not vary frequency response with DC bias, only amplitude. That said, first principles do not consider the lateral charge displacement nor the effect they may have on the frequency response.
In my intial example, I elaborated on a parameter of a system which changed as a consequence of acceleration only, and considered that for the ESL panel. I can only come up with mobility of charge as an entity that can change as a consequence of bias level. I consider RM and his other mention as capable of discerning the difference between amplitude only variation, and some kind of frequency response variation.
As to Streng's conclusions, I emphasize that they absolutely support what I have been saying all along. NOT that he and I are correct, but that we concur. His analysis looks quite good, btw.
As to the 20Khz peak, how is the transformer made? do we have any details on materials and construction? I would ask:
1. is it laminations, and if so, how thick?
2. at 20Khz, they better have used litz. Rs goes nuts at these frequencies when wound into coil form for flux enhancement.
3. Has anybody performed a really good measurement of the transformer? in particular, measurement of LS/Rs of the windings independently no load?
4. Whenever I measure any hf litz constructions, I have to be very careful as the test frequency goes over 5Khz, as the interwinding capacitance can play interesting tricks at the higher registers, resonance being one of them.
It cannot yet be discounted that the 20Khz peak is not a physical charge displacement mechanism caused by an interplay between the lateral sheet resistance and incremental sheet capacitance within the system. Assuming it is an inductance may not be accurate.
I would recommend three approaches.
First, direct measurement of the polar plot of an ESL over a span of DC bias, perhaps 70% to 100% bias.
Second, a thorough measurement of the transformer circuit driving the system.
Third, a set of impedance plots exactly as you showed, but at bias voltages from 0 to 100 %, perhaps every 20%.
If there is an indication that the 20Khz peak is dependent on the bias voltage, that would be a strong indication that the system is not behaving linearly, but is somehow dependent on charge value. (edit: one would also have to consider the time delay parameters of the rings and their drive as well). That would give you the start of a really interesting paper.
jn
ps..one also has to consider physical resonance or a drastic conversion efficiency drop at the peak impedance as well. The one thing I do not like on all impedance measurement graphs is, it only shows unloading with these peaks, not that it is just inductance or resistance.
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