Joe, unfortunately I still fail to see the point you are trying to make.. Everyone who is even vaguely familiar with loudspeaker motor design knows the relationships between magnet strength, mms, pole-piece thickness, wire thickness, vc Rdc...so on and so forth.... That horse has been flogged to death.
So your point being?
So your point being?
Now you've explained this, I didn't know that was what you were trying to say. While we may differ on terminology, it is something that we all understand, so we mustn't let it cloud the discussion. It isn't the point and we have much to talk about.
Yep. Language has limitations. But I know when I see a passive resistor and I am not going to gaslight my own self. If it is outside the gap, it could be anywhere - it is not that hard to figure out.
Maybe I could ask them to go back and at least try to make an effort to understand? Sigh. So I will leave it there. Especially when a third person joins in and sees an opportunity to score cheap points - know what I mean? Seen that happen before, could have written that script.
So let's leave it here for now. Maybe the two of us can continue another time. I have had some great news and nothing is going to dampen that. I believe you know that something from that other thread about my son... he is going to get free treatment for his condition starting tomorrow after they fast-tracked it.
Cheers, Joe
Be brave, post some acoustic measurements, you have nothing to fear from the little piggies.
Voice coil changes resistance with temperature which in turn changes with music. OK?
Eddy currents causes EMK changes, which in turn is dynamically changed by frequency AND apmlitude. This is all dynamic behaviour that is NOT measured easy with a plain sinus wave and THD.
F= B*I*L
F on the driver (force) is B * I * L And B is the magnetic field I is the CURRENT in the driver and L is the length of the wire (coil) that is IN the B field.
From this anyone with some basic electrical knowledge should understand that control over the driver (F) is best (most accurate) done with controlling the current.
I am surprised that this is questioned time after time.
Eddy currents causes EMK changes, which in turn is dynamically changed by frequency AND apmlitude. This is all dynamic behaviour that is NOT measured easy with a plain sinus wave and THD.
F= B*I*L
F on the driver (force) is B * I * L And B is the magnetic field I is the CURRENT in the driver and L is the length of the wire (coil) that is IN the B field.
From this anyone with some basic electrical knowledge should understand that control over the driver (F) is best (most accurate) done with controlling the current.
I am surprised that this is questioned time after time.
The problem isn't technical, it is marketing. Making amps voltage sources gives speaker designers a known source, with which their drivers should work.
If you design a current drive amp, you just can't use any speaker and expect it to work well.
And speaker designers will not design separate versions of their drivers for the one guy who insists on current driver.
Sometimes things just won't happen even if it were the best idea in a century. (Not that I think it is, but that's beside the point).
Jan
If you design a current drive amp, you just can't use any speaker and expect it to work well.
And speaker designers will not design separate versions of their drivers for the one guy who insists on current driver.
Sometimes things just won't happen even if it were the best idea in a century. (Not that I think it is, but that's beside the point).
Jan
But you do. Fact is that a driver has two terminals. And if I connect those two terminals to a voltage source, that driver is voltage driven, by definition.
Now, if you look at that driver, you see an inductance, a resistance, a magnetic circuit, a roll surround, assorted mechanical parts, and the whole of that assembly constitutes the driver and determines it's reaction to the connected voltage source.
What you do is look at that assembly, disregard all the parts except the resistor, and say: 'look, there's a resistor! So it's not voltage drive'!
Just plain BS Joe, sorry.
Jan
anyone, who has measured electrically + acoustically a (low power) current amplifier vs. a voltage amplifier on a (identical) LF driver around its resonance frequency, could maybe share with us the full results?
Interesting are only measurements with a single driver: not 2- or 3-way!
Thanks!
Interesting are only measurements with a single driver: not 2- or 3-way!
Thanks!
Jan, I am afraid here you might be wrong and in deep confusion.
Designing around voltage source is "apparently seen" as more facile for DIY, this much is true.
But surely not everything on market is designed for voltage source, as you say. Some versions are friendlier, or compatible to a certain degree, to current source or some level of intermediate output impedance. Hello valves, remember?
I can stand before my statement: the current source - when done professional, complete and right - can achieve stellar performances which voltage source will never be able to touch. Simply out of reach, by far.
Yes, this amp made by Joe (here to be again clear: he is not the inventor of it) is trivial, basic, not so very good engineered in any aspect, not so desirable, and generally said for many it is a joke. Maybe for him, for most of DIY and for his customers is enough, and I respect his personal evaluation.
But still, generally the performances of current source are at least on solid par with balanced voltage sources. Many (inclusive myself) say CS it is still much better on many accounts. The unbalanced voltage sources should be out from this discussion. Whether you admit it or not, professionals exist which can prove you wrong any day using in their argumentation higher order terms which apparently you have not heard or met them.
Anycase, my best wishes. The old war between VS and CS. CS wins. Peace.
"Thank you Joe for posting a DIY design."
"You are welcome."
"40 Watt Transconductance "Current Amplifier"
Isn't DIY wonderful?
"You are welcome."
"40 Watt Transconductance "Current Amplifier"
Isn't DIY wonderful?
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What I meant was that speakers on the market are designed with voltage drive (an amp with very low Zout) in mind. I agree you can design a speaker for current drive, and probably for very good performance.
My gut feeling, not proven, is that because of the dualism between voltage and current, you can probably design speakers and amps based either on voltage drive or current drive with comparable cost and performance.
But it won't happen because of sunk investments in speakers for voltage drive.
Do you know any speakers designed for current drive?
Jan
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How about making the speaker draw the same current at all frequencies?
That way you cancel out the output impedance of the amplifier and it doesn't matter if it is a voltage source or a current source.
But it is still current through the voice coil, hence:
1. A voltage source is one method, a current delivery system.
2. A current source is another method, also a current delivery system.
All amplifiers are current delivery systems, just different output impedances.
If you equalise the current to be the same at all frequencies, it does not matter whether the output impedance is zero or infinity.
So if it draws 1 Amp at 100 Hertz, make it draw 1 Amp at 1KHz and make it draw 1 Amp at 10KHz and everywhere in between, below and higher.
Now you have turned a whole speaker system into a 'black box' of sorts. It is still leaving a lot of stuff unexplained like my car is a 'black box' would not satisfy anybody. Maybe if we reduced it to only two wheels? Just kidding!
Would anybody accept a loudspeaker system as a black box, after all, it only has two terminals? I think that is a fair question to ask.
Indeed, we should be able to ask exactly what a black box is!
Green = current source.
Red = voltage source.
That way you cancel out the output impedance of the amplifier and it doesn't matter if it is a voltage source or a current source.
But it is still current through the voice coil, hence:
1. A voltage source is one method, a current delivery system.
2. A current source is another method, also a current delivery system.
All amplifiers are current delivery systems, just different output impedances.
If you equalise the current to be the same at all frequencies, it does not matter whether the output impedance is zero or infinity.
So if it draws 1 Amp at 100 Hertz, make it draw 1 Amp at 1KHz and make it draw 1 Amp at 10KHz and everywhere in between, below and higher.
Now you have turned a whole speaker system into a 'black box' of sorts. It is still leaving a lot of stuff unexplained like my car is a 'black box' would not satisfy anybody. Maybe if we reduced it to only two wheels? Just kidding!
Would anybody accept a loudspeaker system as a black box, after all, it only has two terminals? I think that is a fair question to ask.
Indeed, we should be able to ask exactly what a black box is!
Green = current source.
Red = voltage source.
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Joe said:
"How about making the speaker draw the same current at all frequencies?
That way you cancel out the output impedance of the amplifier and it doesn't matter if it is a voltage source or a current source."
Of course the Zout is NOT cancelled! That Zout, together with the (frequency independent) impedance of the speaker determines the current delivered. Double Zout, you halve the current.
And what is the advantage if you make the driver draw the same current over frequency? That in itself doesn't give you anything; I believe what you'd want instead is constant acoustic output over frequency, a flat frequency response. (Possibly corrected for directivity and such).
If that leads to varying current draw over frequency, so be it - we are perfectly able to design amplifiers that have no problem with that.
Jan
"How about making the speaker draw the same current at all frequencies?
That way you cancel out the output impedance of the amplifier and it doesn't matter if it is a voltage source or a current source."
Of course the Zout is NOT cancelled! That Zout, together with the (frequency independent) impedance of the speaker determines the current delivered. Double Zout, you halve the current.
And what is the advantage if you make the driver draw the same current over frequency? That in itself doesn't give you anything; I believe what you'd want instead is constant acoustic output over frequency, a flat frequency response. (Possibly corrected for directivity and such).
If that leads to varying current draw over frequency, so be it - we are perfectly able to design amplifiers that have no problem with that.
Jan