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John Curl's Blowtorch preamplifier part III
John Curl's Blowtorch preamplifier part III
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Old 28th November 2018, 05:59 AM   #10471
Joe Rasmussen is offline Joe Rasmussen  Australia
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Quote:
Originally Posted by john curl View Post
...who knows what else is out there that changes the sound character of the electronics?
I have a suggestion.

What a voltage source does on the current side and that current through a voice coil is what makes the dB-SPL happen, a measurement is being developed right now that will compare the voltage (reference) to current (what makes the sound) and I am optimistic that this might show something up because they will be different. One tells us on the electrical side what we should be hearing and the other what we are actually listening to. Could make 2019 an interesting year.
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Old 28th November 2018, 08:37 AM   #10472
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Quote:
Originally Posted by Joe Rasmussen View Post
I have a suggestion.

What a voltage source does on the current side and that current through a voice coil is what makes the dB-SPL happen, a measurement is being developed right now that will compare the voltage (reference) to current (what makes the sound) and I am optimistic that this might show something up because they will be different.
4 pages on this:

Current drive of speakers and speaker distortion

Current drive of speakers and speaker distortion

Current drive of speakers and speaker distortion

Proudove buzeni repro a zkresleni repro

Last edited by PMA; 28th November 2018 at 08:40 AM.
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Old 28th November 2018, 09:17 AM   #10473
billshurv is offline billshurv  United Kingdom
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John Curl's Blowtorch preamplifier part III
Quote:
Originally Posted by Joe Rasmussen View Post

a measurement is being developed right now that will compare the voltage (reference) to current (what makes the sound) a.

Surely unless you also measure what comes out the speaker you are none the wiser other than some graphs to impress certain types?
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Old 28th November 2018, 09:25 AM   #10474
Joe Rasmussen is offline Joe Rasmussen  Australia
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Thank you.

But this is not about current drive. I thought that was obvious. But say 'current' and that is where the mind goes? No, this is about what the current does under voltage drive. It is still current through the voice coil, no matter what the impedance of the amplifier is - since the only difference between a voltage and current source is the output impedance.

Also, the idea of a V/I conversion under voltage drive has to be questioned, as per first link - there is a better explanation than that one, but it is the one that prevails for now.

I don't think the world will ever be ready for current drive, and probably doesn't need to be, and maybe a better way to deal with current in the voice coil, if we just get a better understanding of it.

I am definitely hoping that somebody will be bringing out an AES paper on this and have a good idea who it will be (not me of course, but if asked, I will happily assist). It could be a game changer, because we want voltage drive to work better.

So hope this helps, the links are fine, got no problems there and current drive is important, just not the right solution.
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Old 28th November 2018, 09:28 AM   #10475
PMA is offline PMA  Europe
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Quote:
Originally Posted by Joe Rasmussen View Post
But this is not about current drive. I thought that was obvious. But say 'current' and that is where the mind goes? No, this is about what the current does under voltage drive. It is still current through the voice coil, no matter what the impedance of the amplifier is - since the only difference between a voltage and current source is the output impedance.
And that is exactly shown.

Current drive of speakers and speaker distortion

as a measurement of distortion of speaker current under voltage drive.

You know, these are mental dances what you are showing.
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Old 28th November 2018, 09:31 AM   #10476
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Thanks PMA, I shall stop fretting about current drive, not that I ever did.....
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Old 28th November 2018, 09:37 AM   #10477
Joe Rasmussen is offline Joe Rasmussen  Australia
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Originally Posted by billshurv View Post
Surely unless you also measure what comes out the speaker you are none the wiser other than some graphs to impress certain types?
Kinda a bit negative, don't you think? Please read the post just before this one.

Re "measure what comes out of the speaker" is not a matter of unless or whatever. I know such measurements already exists and they are able to speak for themselves, so maybe even you will be impressed in the end.

But this is not going to be rushed - but good things come if we just look at this positively, even if some are a bit jaded on the topic and can't see a way forward. But that can change too, so in the end even you might get a little excited too? We shall see.

Anyway, the only reason for the above is because of a comment of JC - he has several times said things like there is still work on the speaker front. He is right. The flaw is not the fact that we don't use current drive. The flaw is that we use the voltage model and have lost focus of what current does under voltage drive. That is (I am about to use the most dangerous word in audio) a new focus. Not new science, not at all. If you don't look, you will not see.
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Old 28th November 2018, 09:42 AM   #10478
billshurv is offline billshurv  United Kingdom
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John Curl's Blowtorch preamplifier part III
Not negative, just reality. What matters is what comes out the speaker. Assuming that current drive more closely matches the movement of a complex electromechanical unit seems to be be starting off from a highly over-simplistic view. If you want to make progress you need to look at the acoustic output as well as the drive waveforms.
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Old 28th November 2018, 09:47 AM   #10479
Joe Rasmussen is offline Joe Rasmussen  Australia
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Originally Posted by PMA View Post
And that is exactly shown.

Current drive of speakers and speaker distortion

as a measurement of distortion of speaker current under voltage drive.

You know, these are mental dances what you are showing.
Oh dear... talk about circular thinking. Often those pointing the finger at others don't realise three fingers are pointing back at themselves... think about it.

Again, this is about improving voltage drive. It is about taking the impedance of the amplifier out of the equation. It is about the speaker designer starting to manage both voltage and current.

Again, the world is not going to be converted to current drive, voltage drive is here to stay, and since F=Bli is the same under voltage and current drive, something seems to be needed: The voltage source cannot control the current, and control is what is needed. And it can be done, with the right techniques employed.
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Old 28th November 2018, 09:57 AM   #10480
Joe Rasmussen is offline Joe Rasmussen  Australia
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Quote:
Originally Posted by billshurv View Post
Not negative, just reality. What matters is what comes out the speaker. Assuming that current drive more closely matches the movement of a complex electromechanical unit seems to be be starting off from a highly over-simplistic view...
Why do you think that this topic is simplistic? Your words, not mine. Nothing simple here, not at all.

Quote:
Originally Posted by billshurv View Post
If you want to make progress you need to look at the acoustic output as well as the drive waveforms.
And why would you think this is not done?

Why the rush to judgement? Good things comes to those who are patient. Several measurements have been done, but more needs to be done. In the end, maybe you will come onboard too. I am not going to be the final author on this, but I can see that somebody will be (could mention a name here, but would rather not), likely next year. That is my hope, 2019 maybe. We shall see.
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