This is correct. A closed box or dipole under current drive, especially large light-weight cones (eg midbass PA 15") exites room a bit differently (typicyll less) than when "brick-walled" with voltage drive or a servo mechanism, alas it also gets exited itself by incident sound pressure/velocity and will ring with its fully undamped mechanical Q when hit with a transient... and it does the same thing with it's own distortion, plus it may get dynamically unstable ("jump resonance") anyway under pure current drive.
You did say a prerequisite was an eq to match spl and phase. I have no problem with that, but it does support my initial concern and question as to whether they are the same.
They are not, and a pre filter is required.
Jn
I suspect Richard is creating a negative damping factor by adding a small amount of positive current feedback along with a lot of voltage negative feedback. The current is picked up by a small resistor in series with speaker ground return, but it has to go to a positive feedback point. Well, Richard, is this what you are proposing?
This seems to be determined by distortion. I've experienced a quite noticably improvement in sound stage depth and clarity when switching to current drive with Air Motion Transformer tweeters.... distortion had dropped by average 10db wideband for all harmonics at low and medium SPL levels.
AMT do not have high levels of back-EMF yet seem to be a type of drivers that responds well to current drive. Lack of thermal compression (with a larger risk of burning out the driver, though), sometimes real issue with smaller AMT's, may have to do with it as well.
OK, this we can certainly agree on ;-). The filter also can be included right in the feedback loop. The filter is benign and not very complex in most cases because pure current drive isn't the best option anyway around resonance where the needed response correction would be strongest.
I tried it both ways: no driver resonance Zobel + feedback eq, and Zobel + much more mild input eq (not in the feedback) and the latter performed better and was less prone to bursts of oscillation at high drive levels at driver resonance.
Kind of a bummer because the components for high-level Zobel are much bigger and expensive, and a smarter engineer could likely figure out a better way, but a conjugate resonance eq in feedback just did not work well.
I have to state I am under contract for my specific method of mixed current/voltage feedback in a studio monitor powered speaker. For this reason I have been asked to stop posting on the subject.
I'm bummed because it is a really fun topic!
Cheers,
Howie
Well enough accepted by who? I generally rate a company by the spec sheet. Janzen get 3 out of 10 in that there are 'some' specifications. But the rest of the product sheet is pure high end marketing BS http://www.jantzen-audio.com/wp-content/uploads/2019/07/Amber-Z-Cap.pdf for example.bill,
this goldenear can hear the difference!
Jantzen is well enough accepted as a better quality and from what I can tell its not just smoke amd mirrors.
And I dont mind spending a little extra for the bling......my next build is gonna be external (visable)
But if you are happy with your purchase and not trying to tell us that our systems will never sound good if we don't use these parts (and this does happen) then all is cool.
No pre-filter required and no inverted signalWasn't it stated that a pre filter was required and that it was an invert of the speaker? That means no speaker swapping, it's no longer a turnkey system.
Dan, you are so incorrect I don't know where to start!!!
Actually, I do. First and third quadrant are resistive. You meant second and fourth.
Jn
??
-RNM
Like this ---> 1985 TAA: Took an existing circuit and upgraded it and added the 0.15 Ohm --- in art I show the before and after THD reduction from the speaker I have also shown that here in this forum before.
View attachment Marsh MFB ckt.pdf
[This is also what Joe is ranting and raving about. BTW ]
So. help Joe; What is the reason THD from speaker was lowered?
THx-RNMarsh
Not yet!
Not so quick, what textbook says the driver is a voltage device? Or do we just have to take your word for it?
Good question. It may be deduced that the phase of the force is coherent with current but phase of acoustic output is another beast that needs further investigation.
Nobody, at any time, has to take my word on anything. In fact, I prefer that nobody does, but instead either understands and agrees, understands but disagrees, or doesn't understand and tries to learn. Valid, well stated conflicting thinking is always welcomed.. My belief is that most learning comes from disagreement, constructive dialogue, and brainstorming.
I have done that three times in the last 25 years, and the results..what I did 24 years ago is still beyond state of the art..granted, it is a high energy physics thing that no normal person understands or cares about. More recently, we made a three order of magnitude improvement on motion control of magnetic devices used to make x rays in a 3rd generation synchrotron.
I do my best to break down every problem into smaller easier to understand components. Not only is keeping it simpler the best way, it makes it much easier for all to understand. Engineering in fact, is by design, the method of breaking complex problems down into easier to understand components...solving each component, then assembling the components into a well understood whole.
Having worked at the highest level of magnetics for a quarter of a century now (actually, I hated typing that..
. ), I am rather confident that I have a better understanding of electrodynamics, energy conversion, EM field theory, magnetic flux containment control and modeling, t line understandings, and even simple inductance understandings... than a tech who has tried to self teach concepts either online or by knowing some audio guys. While I have worked with techs who are significantly better than many engineers I know, they are few and far between.There are quite a few here who can dance circles around those you claim are experts. You really should be trying to learn from those very smart experts rather than aggressively dissing them.
While I feel I know a lot, I am smart enough to know that the posters here have a huge amount of knowledge that I can learn from and draw upon.. The list is huge...and, they are not all phd's and engineers. In fact, I learn the most from the techs that work for me..
So instead of aggressively attacking the smart people here in a feeble attempt to achieve world domination, I recommend you tone it down and act like those here actual know something. You will get a lot farther being nice.
Jn
I am very unhappy that you push me into a position where I feel the need to put you in your place. Please reconsider your stance.
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I never once alluded to that. Why do you fellers get so ruffled about caps and wires?
Things are manufactured, some things are manufactured better than others.
Grizzly,delta,jet,powermatic and several other brands of shop tools are all manufactured at the same plant in Taiwan but vary extensively in quality.
If jantzen products are just glorified crap then they’ve certainly fooled me, but I also like Cornell dubilier, cheap, no frills, no hype......is it ok to use them?
Not only those Bob, almost everything. So many of us are grumpy about marketing stuff. We have all been bitten on our rear side once too often.
Does it even matter? The point in this thread is to talk, not to make sense. Those making sense are strangers in a strange land here.
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I believe Bruno started using some amount of current drive on the Grimmaudio LS1 speakers.
hi JN,
no one is even attempting to answere my questiion at #28172.
Would you take a stab at it, pls. You may be able to help designers develop better drivers and/or amp/spkr interfacing .
THx- RNMarsh
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Yes, but was just a guess as to where to start or how much. My intuition or 'educated guess' I think. Too long ago.* The amp is not a very high OLG amp and I didnt want to push it into instability.
I never went back and tried to "optimize" the values. And, i never did it again to a different amp. Just reportedi t in an obscure little hobby magazine called TAA. Decades later it is Discovered.
Same magazine I brought DA of caps to everyones attention. Ditto dc servo app. TAA = The Audio Amateur.
I agree about sleep... never go to sleep before midnight. Such a waste of time. I think it will be very instructive to be able to explain why such FB lowers THD from the speaker/driver.
*Oh some electrical brain connections are coming thru --- the (-)amp port is summing junction... and phase shift at resonance.
THx-RNMarsh
Or working the problem backwards --- what conditions does the amp need in order to reduce THD further?
THx-RNMarsh
Hand me another can of Red Bull.
I still didn't get an answer. All motors are current devices and nobody's experience is going to change that.
Expert in magnetics, for how many years? I know a few of those too. I will be telling them how wrong they are? Speakers are now voltage devices and they are all wrong? I don't think so. I would be laughed at and ignored. Alas, they know that I would never say that.
There is no textbook that says that motors (and speakers are linear motors) are voltage devices. It is AC current that is the force:
F = Bli
This seems to be the most ignored equation in audio. An inconvenient truth.
Oh, I am aggressive? That's really weird... I mean, that takes the cake.
---
Why are some so desparate to invoke the voltage model when it comes to spakers?
I think I know reason:
When it comes to audio, the voltage model reigns supreme. So everything, including speakers, are viewed accordingly. It must be made to fit the prevailing view. The dominant view.
But those who think that motors are voltage devices, then this here is a fact that must also be reconciled:
Electrostatic speakers are voltage devices.
Expert in magnetics, for how many years? I know a few of those too. I will be telling them how wrong they are? Speakers are now voltage devices and they are all wrong? I don't think so. I would be laughed at and ignored. Alas, they know that I would never say that.
There is no textbook that says that motors (and speakers are linear motors) are voltage devices. It is AC current that is the force:
F = Bli
This seems to be the most ignored equation in audio. An inconvenient truth.
Oh, I am aggressive? That's really weird... I mean, that takes the cake.
---
Why are some so desparate to invoke the voltage model when it comes to spakers?
I think I know reason:
When it comes to audio, the voltage model reigns supreme. So everything, including speakers, are viewed accordingly. It must be made to fit the prevailing view. The dominant view.
But those who think that motors are voltage devices, then this here is a fact that must also be reconciled:
Electrostatic speakers are voltage devices.
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