No intention to offend either. Thank you for the tone, it is a little bit nicer, but this is an area that I am passionate about.
But please trust me on this, I have really done my homework - literally put in the hards yards. So F=BLi is not affected by frequency because the test works for that other frequency too. Do you understand the logic that it is the change that proves the point? If one does not grasp that, then it is a problem to understand it. Maybe you have not yet grasped that logic?
It seems that if we cannot get past F = Bli and the odd reluctance to give it the seriousness it deserves, and then always go into the shell called the voltage model.
That is really at the heart of all this. And I am glad that I have found out. It sharpens my sense of what we are up against. The voltage model!
The only off-topic is speakers? Let you in on something, I joined in when John Curl brought up the topic of speakers. So it can't be entirely verboten, right?
problem to understand it. Maybe you have not yet grasped that logic?
That is a total mischaracterization of my position.
I have quoted a number of textbooks that comport with well-known "electrical laws and terminology" and I do not have problems with people who actually listen. So I don't accept that.
When I quote Langford-Smith, Neville Thiele and Richard Small, I am actually speaking about textbooks, so not my problem then.
Then they were rubbished as antipodeans by a certain American SW here, this is despite the fact that Richard Small is an American. Ouch!
I make a living too. I do OK, but I don't expect to get rich. I'd be doing something else. You have probably been listening to something I have made without knowing it. 😀
Actually no, across the amplifier's terminals. I am not treating the termination impedance of the driver. I am equalising the current of the amplifier, so that the amplifier draws the same current at all frequencies.
Like this 2KHz square wave, Yellow is the voltage of the amplifier, Pink is the current of the amplifier:
That is a measurement of a complete speaker system with 5 drivers per speaker.
I showed this to a highly qualified EE only last week: "Impressive" was his reply. He understood it well.
Is there something here that people don't understand? Plain enough English, OK?
Never used a DC servo motor I see. The primary specification is velocity per volt. They never specify velocity per amp. They can't. They can only specify torque per amp.
An experienced motor engineer would know that. The fact that I have to tell you says a lot.
All the top motion control vendors (you know, the ones who do this for a living) always control the voltage in their motors and amplifiers.
Already said that. You actually don't read the posts do you?
Name dropping without names again. Wow, you've no idea how little that impresses me.
I work brushed servo, brushless DC servo, three phase induction motors (480 volt 100 hp), 3 phase brushless, steppers, as well as soleniodal actuators.
Your "broad brush" schtick on motors is very good to know, as it informs me on your lack of education on this topic.
Your constant appeal to authority instead of presenting any semblance of understanding is also informing.
If you presented me your results on trying to keep the amp operating in quadrants 1 and 3, I too would be amazed. First, at the amount of effort put into something that will never see the light of day, second that you have little understanding of modern solid state amps, and third that you have refined your marketing explanations around ignoring the bulk of engineering knowledge. To wit, you consider actual engineering to be a conspiracy theory.
Very few people consider ignorance of engineering principles to be a plus. You market yourself with that as an asset..
Jn
Sigh, I didn't say I prefer lack of sleep.🙁
I was always an 8 hour kinda guy. Five years ago that changed.
I'm trying to get back to 8...8 solid.
Jn
What harmonics were reduced. What frequencies were affected. What power level. What kind of box. What speaker impedance.
I assumed you had some derivations to share.
Jn
Huh? I did. It was a rhetorical question, and yes I knew the answer.
But you are conflating issues. I get that, this is about the voltage model. I never listened to DC, BTW. My cone gets stuck. 😀
In audio (AC) this model is all-powerful and used to explain most things. Now this is not a dismissal of the voltage model and as you may well know, it has its place.
Take for example an electrostatic speaker. Everything you say can, in voltage terms, can be harmonised there. Look at the behaviour of that kind of speaker and realise that this sort of beast is in fact the opposite in so many ways.
So I ask respectfully, explain the difference... because the way they produce sound is totally opposite to the other. So the real challenge is to come up with explanations for both that are not the same.
Do you follow my drift? Often a good way to understand something is to understand the opposite - like complimentary of sorts.
Also, when I do a real physical test that shows a proportionality between current and the acoustic dB-SPL of a driver 100%, so that if one is changed, the corresponding change is the same, such as double the current brings about the increase of 6dB-SPL. This is pretty solid ground. I am not easily going to be shaken away from it. I feel I have the strongest hand.
Now my challenge is simple, explain to me the difference between a dynamic driver that behaves that way and explain what an electrostatic driver does?
You should not so easily use the voltage model to explain both. Over to you.
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Voltage drive is here to get the flattest frequency response from the conventional electro-dynamic speaker. This is regardless the fact that F = Bli, which is known to everyone who studied speakers theory, where Bl makes a transfer constant in the electro-mechanical model, converting electrical driving to mechanical response (note that F is a mechanical value, NOT acoustical one). Your permanent repeating of F = Bli is boring and brings nothing, everyone knows this.
This is all so very illuminating. And not boring at all.
I have explained a physical measurement and everybody is running away from it. And it does not lie. Fascinating!
Now I fully understand what is going on, now it is so clear. Thank you.
I have explained a physical measurement and everybody is running away from it. And it does not lie. Fascinating!
Now I fully understand what is going on, now it is so clear. Thank you.
Except every long wordy post from you re-inforces that no homework has been done.
Normally I would just ignore you, but the discussion had actually started to become useful again before you turned up and threw a breezeblock in the pond to muss it all up.
No need for trust, I already know that test shows as you say. However I stand by my statement that acoustic output is not exclusively proportional to F, there are other factors at play. I do not wish to ignore any factor at play however inconvenient.
It is not the topic, it's the people. John Curl's Preamp calls into attention extremely minute details not commonly observed such as gate excess current in Jfets. Ideas presented here are dissected into the most minute detail. Any inconsistency, however minute, will come to the surface. It is your choice in the way to deliver an explanation on the fruit of your passion, but presenting it in the form you chose in the past will not gain acceptance, it needs a hefty addition of coherence juice.
As I repeatedly say, I do think your solution have some good merits. Really, not just a figure of speech or being polite.
And Joe, since you are not promoting current drive then the F=BLi discussion is academically interesting but does not lend support to your solution.
Again, no intention to offend anyone. Please keep your temper level and avoid unnecessary sinbin time.
Such test will show exactly the same propoportionality between aplied voltage and SPL...And, as PMA wrote, electro dynamical speakers are designed for flattest frequency response (that is what counts..) with constant voltage aplied..
Could you explain "other factors" as it would need to introduce another source of energy.
This is truly fascinating. The test is correct, as you admit. I am not trying to win an argument. This is about something else and today it has fully dawned on me the full extent of it.
Thank you. I would rather be a positive person than a negative one.
Far from it.
Why is it that so many people have heard the 8 Ohm resistor in parallel with an 8 Ohm (must be a real 8 Ohm as many are not) and heard the difference it makes?
Why don't try it? If you got an amp that can really do low impedances, lower the resistor value even more. Up to you.
I am not by any means an aggressive person, if you knew me in person you would get the exact opposite impression. Please don't think of me in the way you have so far.
It does the same thing as should be immediately obvious from the schematic. The current sense voltage is inverted (the junction between speaker and sense resistor is grounded here), therefore it goes to the non-inverting input of the diff stage.
Your question has been answered IHMO, if you think otherwise then please clarify and detail what's missing.
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It won't be exactly the same, but it will be approximately the same. That shows that acoustic output at a specific frequency is roughly proportional to driving current. We all know that. The same is true for voltage - you seem not to mention this? In addition, for most speakers, the ratio between voltage in and sound out is more constant with frequency than the ratio beween current in and sound out. To follow your logic, that means that speakers are really voltage operated not current operated.Joe Rasmussen said:
Repeating confusion does not make it become clarity, however many times you do it. Perforning an experiment does not add light to a subject if you misinterpret the result of the experiment.
No running, just repeated failed attempts to teach you some basics. Nobody has denied that F=BlI has a role to play in speakers, but it does not mean what you think it means. It does not mean that speakers are necessarily current-driven devices. Even if they were, equalising the impedance seen by the amplifier and leaving the speaker current unchanged would not achieve anything if the amplifier is a conventional voltage source device.
Big question: was the corresponding change of frequency response taken care of, so that always the exact same response was obtained, to at least 0.5dB precision (preferred would be +-0.1dB tolerance)??
If not, such comparisons can end up pretty useless because the change in frequency response dominates the perceived difference (though not necessarily heard as actual frequency response changes, which is the tricky part of this. A +0.3dB change can give the impression of more detail, clearer reverb tails etc without being perceived any "louder").
Well you certainly are enthusiastic, but here you have to decide the kind of support you want. If you want a problem checked and corrected if necessary by some of the best minds out there, you'll find that here.
I agree.
When it was done, I pointed out the same thing. But I also knew something else. That a parallel resitor can also be heard and with similar audible improvement.
There were no FR deviations then, so what has so many have heard?
A flattened current phase angle of the amplifier. The more you flatten it, the better it sounds and it is not that hard to hear.
We have manipulated the current and it sounds better. Hence if points to F = BLi being the real force factor. It always was and always will be.
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