I did not comment on this, but it must be commented on.
As a result of "maxwell", you all now have the ability to view the real component of a driven voice coil's impedance, completely separated from the reactive part.
As a result of "maxwell", you can now view resistive losses with respect to position.
As a result of Demian's test, you have seen the loss component that is velocity related, so can view eddy dragging.
As a result of "maxwell", you can now use a simple pickup coil to completely linearize the drive with respect to variation in Le(x), this being exactly what you want current drive for. But your current drive, for all it's wonders, completely ignores eddy/velocity dependent gap field modulation.
Rejection of understanding by using the phrase "It's time to make measurements and decisions" is beneath you. Please refrain from saying that again. Decisions, you mean like "which pig"?
By now, you should know me. I will not be limited by the impatience or lack of understanding of others, and I will always explain patiently. (as some I work with have done with me over the years)
Do not be afraid of the theory. Understand it.
The complexity of eliminating the distortion mechanisms I speak of is well beyond a simple GPU (graphics processing unit) to solve, as music is very complex.
You want to keep adding bells and whistles to an overly complex ill understood suspension system, I prefer to pave the road and get you off the railroad tracks.
You are looking as far forward as later on today, I look years and decades ahead.
I'm done with catch phrases, I hope you understand..
jn
ps. I enjoy your expertise, and always look forward to more. This has not been a diss on your much appreciated skills.
pps. While Klippel is good, he doesn't understand nor explain it all, I find him not yet "complete". Belief that his knowledge is the end-all is your "pulled hamstring".
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Demian,
This is the kind of analysis that is required.
I've attached a harmonic analysis of the type needed. One could try to use an FFT, but for this need, an FFT is a little bit better than useless as it does give signal power. However, it does not provide any intuitive feel for what is happening. For example, the attached. Yes, I could give the techs and mech engineers an FFT package to evaluate what is going on, but they will not be able to interpret the results sufficiently to diagnose the real problem easily.
Re the pic.
The dark blue is the waveform of interest, it is the error component of a closed loop negative feedback system. It is obviously periodic.
The grey is the fundamental sine. I altered phase and amplitude so that the resultant difference is minimized with respect to that frequency.
What resulted, I then found the next harmonic with lots of signal, it turned out to be third harmonic. So, I again played with phase and amplitude, and cancelled it out as much as possible.
Then, repeated it with the fourth harmonic.
The end result is the orange waveform. What is notable, is that this is no longer a simple periodic waveform. Rather, it is a gated waveform between the fundamental frequency and the fourth. This is a non linearity in the system, one consistent with mechanical gearing. In this case, I know exactly what happens every cycle of the fundamental, and can find physical entities which are affected by torque at the fundamental and fourth. This is all data dropped into excel, btw..
You should:
1. repeat the current vs diff run, taking note of which direction positive current drives the cone.
2. capture at least 40 cycles of the fundamental for both current and difference.
3. transfer it to excel
4. use the periodicity to average the waveform over the 40 cycles. This will clean the waveform up.
5. Fit the resultant error waveform to the current drive by gain subtraction to leave a residual.
6. Perform a harmonic analysis on the residual in the fashion I used here. that will show you the error vs excursion.
For a two tone test, you will require a lock between frequencies. Perhaps 10 times the fundamental, the lock needed for the averaging out function, you don't want to average out the higher tone. This test will show eddy drag modulation of the hf tone.
jn
This is the kind of analysis that is required.
I've attached a harmonic analysis of the type needed. One could try to use an FFT, but for this need, an FFT is a little bit better than useless as it does give signal power. However, it does not provide any intuitive feel for what is happening. For example, the attached. Yes, I could give the techs and mech engineers an FFT package to evaluate what is going on, but they will not be able to interpret the results sufficiently to diagnose the real problem easily.
Re the pic.
The dark blue is the waveform of interest, it is the error component of a closed loop negative feedback system. It is obviously periodic.
The grey is the fundamental sine. I altered phase and amplitude so that the resultant difference is minimized with respect to that frequency.
What resulted, I then found the next harmonic with lots of signal, it turned out to be third harmonic. So, I again played with phase and amplitude, and cancelled it out as much as possible.
Then, repeated it with the fourth harmonic.
The end result is the orange waveform. What is notable, is that this is no longer a simple periodic waveform. Rather, it is a gated waveform between the fundamental frequency and the fourth. This is a non linearity in the system, one consistent with mechanical gearing. In this case, I know exactly what happens every cycle of the fundamental, and can find physical entities which are affected by torque at the fundamental and fourth. This is all data dropped into excel, btw..
You should:
1. repeat the current vs diff run, taking note of which direction positive current drives the cone.
2. capture at least 40 cycles of the fundamental for both current and difference.
3. transfer it to excel
4. use the periodicity to average the waveform over the 40 cycles. This will clean the waveform up.
5. Fit the resultant error waveform to the current drive by gain subtraction to leave a residual.
6. Perform a harmonic analysis on the residual in the fashion I used here. that will show you the error vs excursion.
For a two tone test, you will require a lock between frequencies. Perhaps 10 times the fundamental, the lock needed for the averaging out function, you don't want to average out the higher tone. This test will show eddy drag modulation of the hf tone.
jn
Attachments
Knew you'd chirp up with the pom poms, anything to diss me.
Pavel and I already agree on the other aspects, especially suspension non linearities. That is only part of the problem. They don't explain intermodulation that he provided us test results for.
problem 1: the magnetic non linearities I speak of are by design for roughly 100 years. It's about time to address them. Simply saying Qms is changed by an aluminum former is insufficient.
Problem 2: People who are uncomfortable trying to understand and accept new knowledge. You obviously seem to prefer that category..
If you (and anybody else) are happy following another's footsteps without any desire to advance the SOTA, that is just fine. Many people are happy not leading.
Just remember, the scenery never changes for the second dog. You may be content with unchanging scenery, I am not. I have grey matter in between my acoustic gathering devices and I have every intention of using it.
While I listed "people unwilling to learn" second, in order of importance, they are the biggest hindrance to advancement. To quote a wise sage... lead, follow, or get out of the way.
jn
ps. I'm sure you can come up with some good 50 year old anecdote, right??
pps..Condemnation without examination.....hmmm, where have I read that before??
As I've always said John, your expertise is valued, perhaps you should actually take it out for a spin??
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I tried to be polite about it, but a more direct approach might be necessary.
Most of us live with loudspeakers that are made available to us from commercial sources. Some are amazingly cheap and others may cost more than $1000 per driver. What is the difference? For the record, people have looked into making 'cost effective' loudspeaker drivers for the last 90 years, at least. Trial and effort made 'successful' drivers from at least 80 years, (the earliest example that I lived with) and continuous efforts have been made to improve loudspeaker drivers since.
Now, could there be a breakthrough here? Maybe, but it has not been shown here yet. At least not beyond what 'current drive' might give in some cases.
Many here would do well by learning what has been done already by reading through a book by Olsen, or another real 'expert' in the design of loudspeaker drivers, and getting an overview of what loudspeaker drivers are made of, and why some examples are more successful than others. One fundamental question is why 2 loudspeaker drivers, both the same approximate diameter, can be so different in price? Yes, there really are significant differences, and this is the usual reason for a 100:1 price ratio on occasion.
What I see here is a discussion of a specific area that we normally have little control over, and most of the loudspeaker's distortion will be dependent on the design quality of the loudspeaker driver for the most part, not whether it is driven by voltage, current, or any other sort of drive.
Most of us live with loudspeakers that are made available to us from commercial sources. Some are amazingly cheap and others may cost more than $1000 per driver. What is the difference? For the record, people have looked into making 'cost effective' loudspeaker drivers for the last 90 years, at least. Trial and effort made 'successful' drivers from at least 80 years, (the earliest example that I lived with) and continuous efforts have been made to improve loudspeaker drivers since.
Now, could there be a breakthrough here? Maybe, but it has not been shown here yet. At least not beyond what 'current drive' might give in some cases.
Many here would do well by learning what has been done already by reading through a book by Olsen, or another real 'expert' in the design of loudspeaker drivers, and getting an overview of what loudspeaker drivers are made of, and why some examples are more successful than others. One fundamental question is why 2 loudspeaker drivers, both the same approximate diameter, can be so different in price? Yes, there really are significant differences, and this is the usual reason for a 100:1 price ratio on occasion.
What I see here is a discussion of a specific area that we normally have little control over, and most of the loudspeaker's distortion will be dependent on the design quality of the loudspeaker driver for the most part, not whether it is driven by voltage, current, or any other sort of drive.
Attachments
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Was Demian's measurement taken with the cone locked or not? I think we need some way to isolate the different magnetic effects we're looking for.
This thread has some Z(x) charts:
XBL^2 design drawbacks? -
Techtalk Speaker Building, Audio, Video Discussion Forum
It shows some interesting activity, but unfortunately you can't tell which line belongs to which.
EDIT: Here is a Z(x) chart from my model. Nonlinear suspension is not enabled.
This thread has some Z(x) charts:
XBL^2 design drawbacks? -
Techtalk Speaker Building, Audio, Video Discussion Forum
It shows some interesting activity, but unfortunately you can't tell which line belongs to which.
EDIT: Here is a Z(x) chart from my model. Nonlinear suspension is not enabled.
Attachments
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Big Wilson Audio loudspeakers are a good example of a low distortion design. Bass drivers have to be big, to have large cone area, which makes it possible for them to work with low or moderate cone excursion, and distortion is kept low. $20 toys or small speakers will never do it. One just needs to move with a lot of air, that's the key. I agree with JC.
To be fair, I don't think JC's "chirps" are about you specifically. More like he is not comfortable with a topic of discussion where his expertise is not especially useful.
You need to practice your people skills.
1000 dollars for a magnetically based actuator. That is not expensive. Move the decimal point two places and you start talking money.
I believe you meant trial and error..
Yah, you can continue with your trial and error if you wish, and slough off anybody who brings actual conceptual, engineering, and physics understanding to the game. That's how you roll, not me.
What best to say....patience grasshopper...
And yet, you are still happy with 1 to 5% distortion, intermodulation products? Luckily, some people don't even call that a near miss.
Isn't that a strawman?
And if you have it your way, nobody will ever advance it. The reason you have little control over it is because you don't understand it, can't measure it, so cannot do anything about it other than handwave.
That is not me.
20, 30 years ago I would have been discouraged by your attitude. Now, I certainly know better. You tend to just bring fluffy pom poms to the table, with no technical discussion or merit. Why is that??
ps...John, let me guess...that book is what, 50 years old? You do understand significant advances in magnetics have been made in the intervening decades. I wonder, maybe you could talk to some magnetics guy who is working on some of the most advanced magnetic structures on the planet..nah, where would you find a resource such as that??
jn
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Come now, John, do you really think most readers here don't understand why two drivers of the same diameter can have vastly different prices? I think the discussion here has already covered driver differences far more interesting than anything in those pages you shared. I mean underhung and overhung coils have already been mentioned here many timed, accompanied by actual analysis of their effects on efficiency and distortion. Those illustrations from that old book are not adding much to the discussion.
Pavel: And yet Bruno seems to be doing a pretty good job with multiple small drivers and lots of DSP? I haven't seen real distortion measurements for the Kii but they must be out there? Would be interesting to see the distortion he gets.
I'm firmly in the systems camp on this. Treating an amplifier in isolation and a speaker equally in isolation gives us suboptimal performance. you have to treat both together and look at new ways of approaching the problem. Obviously you will never get a small woofer (devaliet anyone) to sound like a Danley Jericho but there must be better ways of doing things if only for us daft DIY types
I'm firmly in the systems camp on this. Treating an amplifier in isolation and a speaker equally in isolation gives us suboptimal performance. you have to treat both together and look at new ways of approaching the problem. Obviously you will never get a small woofer (devaliet anyone) to sound like a Danley Jericho but there must be better ways of doing things if only for us daft DIY types
That one was. However, you and I are in agreement. He is not comfortable when he is not useful. Which is extremely unfortunate. Pavel is showing some of that tendency as well. For some strange reason, I keep "wandering" between the "don't know what he's talking about", "is just incorrect", "looking where there is no problem", and now, "trial and error is the way to advance" and there are "bigger fish to fry".
Real advancement is not throwing stuff against the wall and looking at what sticks. Magnetics has come such a long way, but some people are destined to defend 100 year old design methodologies to the end...
jn
Or you can use several little drivers, with the advantage of getting less membranes deformations and more acceleration, while keeping the advantages of the big surface for little excursion ?
More than this, if we place those speakers in various positions in your listening room, keeping their distances to you in such a way they have few influence on their respective propagation delays to your ears (Sub basses) you'll have the chance to minimise the resonance modes of the room.
Only difficulty: to find a little speaker with a high enough efficiency, low resonance frequency and appropriate Thiel and Small parameters for what we want to do with them.
A new life for acoustic suspension type drivers, sacrificing efficiency ?
And, if the Jneutron idea reveals itself as preaching tangible results in real use, only one of them could be used as a model to power the others.
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Yes of course, but, IME, 2 (e.g.) smaller woofers sound different than one bigger woofer with the same cone area as sum of the small ones. This is interesting and I do not have an exact explanation why. To me, bass is more "natural" from one bigger woofer.
Such an odd statement in that link, that Le(x) correlates to Z(x)
And that (x) is frequency.
Isn't Le(x) inductance vs x as in "xmax". Where in any of those plots is reference to the position of the voice coil with respect to the gap? Did I miss something?
Do we need a clear and concise definition "rosetta stone" so we are all talking about the same thing?
jn
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Agree. And, may-be I have an explanation for this ;-) (differences in QTS, Theil and small, bass reflex VS closed boxes etc.)
Need to be explored comparing using them only in the ultra bass area (< 50Hz or so) with active digital filter to optimize their raccordement, that i had never tried seriously. Lazyness.
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