Oh my god! I didn't say that. There are not two linear systems it is one system that can be behave linearly or not linearly and this can also depend on the way it is driven.
Ah now it is obvious!! I was just waiting for this. So why don't you tell me how a transducer works and what those terms look like. Where the linear or non-linear behaviour is coming from? I am all ears. Let's see how obvious is.
You did say that, more than once. Most recently in post 102:45 said:
Is this statement made by some other '45' and not you? Or have Jan and I imagined it, or seriously misunderstood it?45 said:
a System description should be independent of the driving Z
just because a System responds "more linearly" to "current drive" doesn't let us call it a Linear System if it shows significant nonlinearity with "voltage drive"
characterizing a system adequately can involve quite a few test signals and conditions
I think many would start with characterizing a unkown system's Z vs drive level as well as frequency - which would quickly show typical dynamic speaker nonlinear behavior
how does any of this relate to the thread topic on Putzey's Negative feedback comments
just because a System responds "more linearly" to "current drive" doesn't let us call it a Linear System if it shows significant nonlinearity with "voltage drive"
characterizing a system adequately can involve quite a few test signals and conditions
I think many would start with characterizing a unkown system's Z vs drive level as well as frequency - which would quickly show typical dynamic speaker nonlinear behavior
how does any of this relate to the thread topic on Putzey's Negative feedback comments
Feedback can only help a system which is already reasonably sensible e.g. no discontinuities or chaotic behaviour. Pathological systems just get worse when feedback is applied.
Ehmmm but according to DF96 it should be obvious! He knows everything....!!! He knows that for voltage drive a specific driver is needed and for current drive another kind of driver is needed.
What does this mean? It doesn't mean anything. Total nonsense. There is no specific requirement. The same driver can be succefully used with both!!
Ideally you would like to have a constant compliance and that might the illusion while mesuring the usual T/S parameters. In reality that is never strictly true for large signals (that's why the historical name of transient distortion has been dropped in common use) and so the force depending on the displacement is at least parabolic.
However 99.99% people use a constant voltage source, at least for assessing a driver.
There are cases of drivers where, under certain design choices AND current drive, compliance can be fairly constant and thus the system is fairly linear. It is obvious that this problem is more relevant for a woofer.
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That's what I have found so far and I have spent enough time on it, I think. So as I am not a professionst in audio I will leave that to others. I am more interested in listening music in the best possible way which requires a lot of effort in too many areas and now the time I have is less and less.
Well, if you have current drive there is no (or minimal in real case) back EFM which is a feedback form. I am not sure if it was cited for this reason though....rather the reason might be that the constant current source would be a pentode amp with no feedback.
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If you read the book of Esa Merilainen (sp?) it will be clear that current drive or voltage drive require differently optimised drivers.
Hans Polak reviewed the book in Linear Audio and came to the same conclusion.
Yes you can literally use any driver with any drive circuit, but for optimum results, you need different ones.
Even for closed box or bass reflex with voltage drive you already have differently optimised drivers.
There is so much literature out there that you can study.
Jan
OK, quick thought: what is the cause of back EMF? and why would that cause magically disappear with current drive? (hint: it does not).
Please, think about it. I think you will find that 1) it is still there (of course) and b) due to absence of amplifier damping, its effect is huge compared to voltage drive.
Jan
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I know the Merilainen book. There is a difference in the approach: he can only use a commercial product off-the-shelf I can get one better.
I repeat, getting a linear behavior is the real thing. All the rest is peanuts....
I repeat, getting a linear behavior is the real thing. All the rest is peanuts....
I don't have to think! I measure the impulse response and except for one single and very acceptable overshoot the decay is faster and cleaner.
This is also becuase of the linear behaviour of the driver.
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