Nania:
I really want to get a handle on this. Often, people cannot, for whatever reason, convey what they have in mind because a host of things get either unsaid or improperly said.
The people who are NOT flaming you need more info and maybe if we pick at you, one intelligent question at a time, we can come to an understanding.
So, here is my intelligent question. Does your idea rest on the thought that the speaker changes the input to itself?
Do I hear anyone laughing?
I really want to get a handle on this. Often, people cannot, for whatever reason, convey what they have in mind because a host of things get either unsaid or improperly said.
The people who are NOT flaming you need more info and maybe if we pick at you, one intelligent question at a time, we can come to an understanding.
So, here is my intelligent question. Does your idea rest on the thought that the speaker changes the input to itself?
Do I hear anyone laughing?
I'm not quite clear on where the theory is coming from, but I agree that it would be nice to get where I think it's going.
How's that for an opaque statement?
Let me come at this from another angle. Tube amps (generally having a fairly low damping factor) do not generally excel in the bass region. Okay, so far, so good. Then along comes a piece like my old Conrad Johnson Premier One. Wonderful bass.
<i>What?</i>
Still a comparatively low damping factor, but the bass was as tight and defined as you could ask for. Large amps as a class are sometimes capable of things (even when operating at low power) that smaller amps aren't capable of. Nelson alluded to this in another thread recently, mentioning that the big X amps, despite poorer damping factors, had better bass than some of the smaller models.
Okay...so it's easy to say that maybe damping factor isn't the be-all, end-all descriptor of low and response. But still, maybe there's something else involved.
Something no one else has mentioned yet is that reactive components <i>do</i> 'separate' the voltage from the current, either leading or lagging. Now, work backwards into the amplifier and see how amplifier A responds to that, vs. amplifier B. There could easily be some variance in the ability of an amplifier to throw a voltage into the (reactive) speaker, then follow it with the current at some arbitrary phase lag.
Come at this from yet another direction. Purely resistive loads such as the Magneplanars are generally regarded as sounding good. Setting aside the reactance of the passive crossover components for the moment (let's pretend we're biamping, for instance), is this why purely resistive drivers often sound better? Because they <i>don't</i> separate the voltage and current, and the amplifier is more able to supply a 'perfect' signal?
What is the sound of music when reactive components grease the clutch and the voltage and current slide apart; not arriving at the same time? To the extent that you choose to look at a speaker as a "current driven" device, the voltage peak might arrive and depart without the speaker reacting the way you would initally expect...it's still waiting for the current waveform. Can anyone think of a way to devise a real-world speaker load where one could vary this in real time and listen to the effect on the sound? I'm not sure this can be easily done and maintain flat frequency response, etc. but it would be instructive. Any ideas, Bill?
Yes, it's easy enough to trot out Ohm's Law and such. But don't act nasty about it. Ohm's Law is a formula, not a club to beat someone over the head with. Whether this idea floats or not, people need to let their imaginations roam. It's how new concepts arrive on the scene.
Nania, assuming that I'm anywhere in the ballpark of what you're thinking, might I suggest that you begin by using one trace on the scope to read the voltage on a real world speaker while the other reads the voltage across a very small resistor--perhaps .01 ohms--in series with the speaker; hence reading the current. You may have to try different frequencies to find a spot where the amp/crossover/driver combination is really cutting up. For instance, try woofer resonance, crossover points, etc. Also try different waveforms: sine, square, triangle, sawtooth, whatever you can get your hands on. Then work from there to see if you can relate the degrees of phase rotation to what the listener hears. You've been using the word image somewhat loosely perhaps, but I think that you'll find that the image (in the more strictly defined sense of the listener's impression that a particular musician is right <i>there</i>) is quite sensitive to phase changes. It might easily turn out that ripping the voltage and current asunder might cause the image to deteriorate.
Grey
How's that for an opaque statement?
Let me come at this from another angle. Tube amps (generally having a fairly low damping factor) do not generally excel in the bass region. Okay, so far, so good. Then along comes a piece like my old Conrad Johnson Premier One. Wonderful bass.
<i>What?</i>
Still a comparatively low damping factor, but the bass was as tight and defined as you could ask for. Large amps as a class are sometimes capable of things (even when operating at low power) that smaller amps aren't capable of. Nelson alluded to this in another thread recently, mentioning that the big X amps, despite poorer damping factors, had better bass than some of the smaller models.
Okay...so it's easy to say that maybe damping factor isn't the be-all, end-all descriptor of low and response. But still, maybe there's something else involved.
Something no one else has mentioned yet is that reactive components <i>do</i> 'separate' the voltage from the current, either leading or lagging. Now, work backwards into the amplifier and see how amplifier A responds to that, vs. amplifier B. There could easily be some variance in the ability of an amplifier to throw a voltage into the (reactive) speaker, then follow it with the current at some arbitrary phase lag.
Come at this from yet another direction. Purely resistive loads such as the Magneplanars are generally regarded as sounding good. Setting aside the reactance of the passive crossover components for the moment (let's pretend we're biamping, for instance), is this why purely resistive drivers often sound better? Because they <i>don't</i> separate the voltage and current, and the amplifier is more able to supply a 'perfect' signal?
What is the sound of music when reactive components grease the clutch and the voltage and current slide apart; not arriving at the same time? To the extent that you choose to look at a speaker as a "current driven" device, the voltage peak might arrive and depart without the speaker reacting the way you would initally expect...it's still waiting for the current waveform. Can anyone think of a way to devise a real-world speaker load where one could vary this in real time and listen to the effect on the sound? I'm not sure this can be easily done and maintain flat frequency response, etc. but it would be instructive. Any ideas, Bill?
Yes, it's easy enough to trot out Ohm's Law and such. But don't act nasty about it. Ohm's Law is a formula, not a club to beat someone over the head with. Whether this idea floats or not, people need to let their imaginations roam. It's how new concepts arrive on the scene.
Nania, assuming that I'm anywhere in the ballpark of what you're thinking, might I suggest that you begin by using one trace on the scope to read the voltage on a real world speaker while the other reads the voltage across a very small resistor--perhaps .01 ohms--in series with the speaker; hence reading the current. You may have to try different frequencies to find a spot where the amp/crossover/driver combination is really cutting up. For instance, try woofer resonance, crossover points, etc. Also try different waveforms: sine, square, triangle, sawtooth, whatever you can get your hands on. Then work from there to see if you can relate the degrees of phase rotation to what the listener hears. You've been using the word image somewhat loosely perhaps, but I think that you'll find that the image (in the more strictly defined sense of the listener's impression that a particular musician is right <i>there</i>) is quite sensitive to phase changes. It might easily turn out that ripping the voltage and current asunder might cause the image to deteriorate.
Grey
Now Grey what you have just said is something i can find the time to investigate... perhaps this is what Nania meant all along but didnt express it as well as you have... I have in the past thought about the same effects as you mention...
It is still not possible for an 2 amplifiers to do the 8mV & 2 Amps or 8Amps & 2mV thing into the same driver with the same input but perhaps if Nania rethought what he is saying he may decide that what he actually means is 8V & 1 Amps under 3 different circumstances ie. with 3 different drivers ... 1st with current leading voltage, 2nd with voltage and current aligned and 3rd with current trailing voltage .... The trouble with this is that we are now venturing into an area that is primarily determined by the speakers used not the amplifier but in as much as certain amplifiers are more capable of driving highly reactive loads, the experiment could still prove useful although not for the purpose outlined in the original post.
It is still not possible for an 2 amplifiers to do the 8mV & 2 Amps or 8Amps & 2mV thing into the same driver with the same input but perhaps if Nania rethought what he is saying he may decide that what he actually means is 8V & 1 Amps under 3 different circumstances ie. with 3 different drivers ... 1st with current leading voltage, 2nd with voltage and current aligned and 3rd with current trailing voltage .... The trouble with this is that we are now venturing into an area that is primarily determined by the speakers used not the amplifier but in as much as certain amplifiers are more capable of driving highly reactive loads, the experiment could still prove useful although not for the purpose outlined in the original post.
Load Dependant Systems
Hello Gray and AF, I agree with what you are saying.
I think nania is expressing amp-cable-loudspeaker load interdepencies, and the resultant interface imd.
Most amps are correct into a resistive load, but come unstuck on badly reactive cable- loudspeaker loads.
My experience in precisely compensating drivers with shunt RC networks is that the amplifier is able to deliver much cleaner and more powerfully (stronger), and much extended system frequency response in the lows, mids clean and immediate and highs going out past hearing range.
Overhang decay/ringing/noise is quenched and spaces are darker, more correct transients, bigger apparent dynamic range and fantastic depth imaging - these are all products of lessened overall system imd.
With conventional loop NFB amplifiers this load sensitivity is to be expected, and tube amplifiers enjoy attenuation through the output transformer of the slew rate of both the send pulse, and of the return pulse, and therby are less prone to inductively reactive loads.
Nania is correct in that saying that a reactive driver will always cause phase distortion in the transduced sound pressure pulse.
RC networks do not fix the driver phase characteristics, but they do present an overall resistive load to the amplifier and this alone can pay distinctly big sonic dividends.
The resistive panel drivers that grey speaks of ought to be phase flat, and any amp would be happy driving them, and the sonic result ought to be pleasing, and yes dynamic cone driver lows could be sonically mismatching.
AF, maybe you can try a monte-carlo experiment with different driver shunt RC networks with non/under/over, resistance/capacitance WRT critically compensated driver, and determine some sonic differences.
Regards, Eric.
Hello Gray and AF, I agree with what you are saying.
I think nania is expressing amp-cable-loudspeaker load interdepencies, and the resultant interface imd.
Most amps are correct into a resistive load, but come unstuck on badly reactive cable- loudspeaker loads.
My experience in precisely compensating drivers with shunt RC networks is that the amplifier is able to deliver much cleaner and more powerfully (stronger), and much extended system frequency response in the lows, mids clean and immediate and highs going out past hearing range.
Overhang decay/ringing/noise is quenched and spaces are darker, more correct transients, bigger apparent dynamic range and fantastic depth imaging - these are all products of lessened overall system imd.
With conventional loop NFB amplifiers this load sensitivity is to be expected, and tube amplifiers enjoy attenuation through the output transformer of the slew rate of both the send pulse, and of the return pulse, and therby are less prone to inductively reactive loads.
Nania is correct in that saying that a reactive driver will always cause phase distortion in the transduced sound pressure pulse.
RC networks do not fix the driver phase characteristics, but they do present an overall resistive load to the amplifier and this alone can pay distinctly big sonic dividends.
The resistive panel drivers that grey speaks of ought to be phase flat, and any amp would be happy driving them, and the sonic result ought to be pleasing, and yes dynamic cone driver lows could be sonically mismatching.
AF, maybe you can try a monte-carlo experiment with different driver shunt RC networks with non/under/over, resistance/capacitance WRT critically compensated driver, and determine some sonic differences.
Regards, Eric.
that sounds like a good thing to investigate :
but how can it be arranged?
With current trailing voltage, this is easy because you have inductance from a traditional coil 'speaker
With current aligned voltage, electrostats almost do this and people do say they sound great
Current leading voltage, how can you arange this? Putting a cap on a speaker creates a crossover and large capacitance can lead some amps to occilate.
but then you are comparing three completly diffrent types of drivers which have there different uses a bit like apples and oranges.🙄
hmmmmmm
This is something worth thinking about
but how can it be arranged?
With current trailing voltage, this is easy because you have inductance from a traditional coil 'speaker
With current aligned voltage, electrostats almost do this and people do say they sound great
Current leading voltage, how can you arange this? Putting a cap on a speaker creates a crossover and large capacitance can lead some amps to occilate.
but then you are comparing three completly diffrent types of drivers which have there different uses a bit like apples and oranges.🙄
hmmmmmm
This is something worth thinking about
Sweeping Values.
I meant as one experiment to over compensate with too much capacitance, and yes some amps will not tolerate this.
By monte-carlo I mean to sweep both the resistor and capacitance values and from that derive an experimental conclusion.
Regards, Eric.
I meant as one experiment to over compensate with too much capacitance, and yes some amps will not tolerate this.
By monte-carlo I mean to sweep both the resistor and capacitance values and from that derive an experimental conclusion.
Regards, Eric.
Hi Guys,
The other one you also need to include is the inductive back-emf produced by the voice coil acting as a transformer when it is moving through the magnetic flux.
Also, remember that the measured ratio of inductive, capacitive and resistive effects can be dependent on this back-emf, and result in VERY different effects during steady state signals, to those seen due to transients...
In the end, I think that Nania is the victim of never having had Ohm's Law explained properly in conjunction with Reactance, Resistance, and the "Complex Plain".
This is a profound and beautiful subject once you understand it, but from the outside, it seems convoluted, impenetrable, and largely irrelevant to today's EE syllabus. The modern courses seem to devote less and less time to it... Sad.
Bill.
P.S. I went through the same pain myself when I first encountered the counterintuitive nature of much of this stuff. It took me months to master, because like Nania, I tried to understand what the formulae were actually telling me.
The other one you also need to include is the inductive back-emf produced by the voice coil acting as a transformer when it is moving through the magnetic flux.
Also, remember that the measured ratio of inductive, capacitive and resistive effects can be dependent on this back-emf, and result in VERY different effects during steady state signals, to those seen due to transients...
In the end, I think that Nania is the victim of never having had Ohm's Law explained properly in conjunction with Reactance, Resistance, and the "Complex Plain".
This is a profound and beautiful subject once you understand it, but from the outside, it seems convoluted, impenetrable, and largely irrelevant to today's EE syllabus. The modern courses seem to devote less and less time to it... Sad.
Bill.
P.S. I went through the same pain myself when I first encountered the counterintuitive nature of much of this stuff. It took me months to master, because like Nania, I tried to understand what the formulae were actually telling me.
Dear friend nania.
nania.
Glad to meet someone who understands Audio.
Many people use their time evaluate
cables
connectors
resistors
Other try to optimize the "1" and "0" of digital signal
some are trying to turn 0.001% distortion in preamps to 0.0001%
Other try to reduce 0.01% to 0.001% in Power-amps.
At a given time, this year, we have a certain component situation.
This is not a static thing. Components are invented
and improved all the time.
I think peole with good sense, in todays situation,
should spend more time in dealing with that area
you point out.
This is the moment when the information that is present
in Electric Energy, must be Converted into Mechanical Energy.
This has to be done as "sound"
is airpressue fluctuations
we can percept with Sensors, called "ears".
The distortion after that Convertion,
suddenly is messured into Integers of %.
So we should focus more on Room-acoustics/LSP/LSP-driving-techniques.
It is here we have some gains to attain,
when it comes to effecting our ears.
But this assumes that we want High Fidelity.
Fidelity, what is that?
To be totally true to.
In this case the air pressure
preseneted to michrophones, at recording,
should be reproduced to our ears, in listening.
Preferable in a room that is a copy of recording room.
---------------------------------------------------------------
This statement is my view of this years situation.
It might come a situation in future,
when other matters in the signal chain
will have to have more attention from designers/inventers.
So I welcome a sensible man, that has understood
where he should put his effort.
This man's name "nania", deserves to be highlighted!
gromanswe
one step ahead
with nania
nania.
Glad to meet someone who understands Audio.
Many people use their time evaluate
cables
connectors
resistors
Other try to optimize the "1" and "0" of digital signal
some are trying to turn 0.001% distortion in preamps to 0.0001%
Other try to reduce 0.01% to 0.001% in Power-amps.
At a given time, this year, we have a certain component situation.
This is not a static thing. Components are invented
and improved all the time.
I think peole with good sense, in todays situation,
should spend more time in dealing with that area
you point out.
This is the moment when the information that is present
in Electric Energy, must be Converted into Mechanical Energy.
This has to be done as "sound"
is airpressue fluctuations
we can percept with Sensors, called "ears".
The distortion after that Convertion,
suddenly is messured into Integers of %.
So we should focus more on Room-acoustics/LSP/LSP-driving-techniques.
It is here we have some gains to attain,
when it comes to effecting our ears.
But this assumes that we want High Fidelity.
Fidelity, what is that?
To be totally true to.
In this case the air pressure
preseneted to michrophones, at recording,
should be reproduced to our ears, in listening.
Preferable in a room that is a copy of recording room.
---------------------------------------------------------------
This statement is my view of this years situation.
It might come a situation in future,
when other matters in the signal chain
will have to have more attention from designers/inventers.
So I welcome a sensible man, that has understood
where he should put his effort.
This man's name "nania", deserves to be highlighted!
gromanswe
one step ahead
with nania
Hi Nania
It is in fact true that current-drive of a loudspeaker would have it's advantages over voltage drive. Since the force generated by the voice-coil is proportional to the CURRENT flowing through it.
So the drive linearity would be increased and the effect of the voice-coil inductance would be eliminated.
But as ever, there's no free lunch:
1.) All the known laws of physics are still valid (I hope noone's foolish enough to believe the contrary). Just as an example: If you input a fast transient to your amp/driver combination, the peak output voltge your amp needs to be capable of has to be huge. This would be the price you pay to get around the current lagging effect of the voice-coil inductance. And you simply can't compare voltage drive as hitting- and current drive as guiding a voice-coil !
2.) Around the driver's fs this combination would loose the control over the cone-motion. So that you will either have to use it for mid- and high- frequency drivers (which are usually used well above their resonant frequency) or your amp has to act as avoltage source at the lower end and as a current source above !
3.) The technique would only be useful for single-driver loudspeaker- or active- systems because a multiway passive loudspeaker would make everything much more complicated.
Me personally (despite being a fan of active speakers), I stick with voltage drive because it is much simpler. The voice-coil of the broadband transducer I use has only 18 Microhenries of coil inductance anyway (despite of it's lin x-max of +- 3.5 mm and a voice-coil diameter of 75 mm)!*
I personally have experienced what others say (Nelson Pass et al) that generally more beefy amplifiers have better grip on the loudspeaker even though some of them don't sport fancy damping-factor values.
An often neglected factor is the increased power loss in the output stages when driving reactive loads. Many SS amplifiers are made perfectly short-circuit proof by using protection circuits whose current protection threshold value changes proportional to the output voltage. While these are perfectly protected aginst misuse they will have limited drive capability into non resistive loads.
A generously dimensioned output stage would have it's merits here (or the use of these rugged but unloved HEXFETs). BTW anybody ever had the opportunity to hear how much slam a class-d amplifier has in the bass range despite sometimes only moderate output power specifications ?
Kind regards
Charles
* To cite John Watkinson: If you want to build good loudspeakers, then you need good drivers !
It is in fact true that current-drive of a loudspeaker would have it's advantages over voltage drive. Since the force generated by the voice-coil is proportional to the CURRENT flowing through it.
So the drive linearity would be increased and the effect of the voice-coil inductance would be eliminated.
But as ever, there's no free lunch:
1.) All the known laws of physics are still valid (I hope noone's foolish enough to believe the contrary). Just as an example: If you input a fast transient to your amp/driver combination, the peak output voltge your amp needs to be capable of has to be huge. This would be the price you pay to get around the current lagging effect of the voice-coil inductance. And you simply can't compare voltage drive as hitting- and current drive as guiding a voice-coil !
2.) Around the driver's fs this combination would loose the control over the cone-motion. So that you will either have to use it for mid- and high- frequency drivers (which are usually used well above their resonant frequency) or your amp has to act as avoltage source at the lower end and as a current source above !
3.) The technique would only be useful for single-driver loudspeaker- or active- systems because a multiway passive loudspeaker would make everything much more complicated.
Me personally (despite being a fan of active speakers), I stick with voltage drive because it is much simpler. The voice-coil of the broadband transducer I use has only 18 Microhenries of coil inductance anyway (despite of it's lin x-max of +- 3.5 mm and a voice-coil diameter of 75 mm)!*
I personally have experienced what others say (Nelson Pass et al) that generally more beefy amplifiers have better grip on the loudspeaker even though some of them don't sport fancy damping-factor values.
An often neglected factor is the increased power loss in the output stages when driving reactive loads. Many SS amplifiers are made perfectly short-circuit proof by using protection circuits whose current protection threshold value changes proportional to the output voltage. While these are perfectly protected aginst misuse they will have limited drive capability into non resistive loads.
A generously dimensioned output stage would have it's merits here (or the use of these rugged but unloved HEXFETs). BTW anybody ever had the opportunity to hear how much slam a class-d amplifier has in the bass range despite sometimes only moderate output power specifications ?
Kind regards
Charles
* To cite John Watkinson: If you want to build good loudspeakers, then you need good drivers !
Well, alot has happened since I last signed off!
gromanswe
Thank you for your welcome
woneill
I hate to think of myself as any kind of victum but some of the posts in this thread have made me feel like one. My fundamentals in the study of electronics may not match some of those in this forum but they are sound (pun intended). The THD numbers currently in use are based on fixed frequency inputs and as such are useless in predicting how well music will be represented IMHO. That is where the impetus for my quest of a new standard and measurement initiated.
mrfeedback
AudioFreak
Mr. Grey Rollins
Bill Fitzpatrick
As one the first people who saw a little sense in my idea, I owe you a thanks. That said, my idea will become clearer if you try to unlearn the idea that current is a result of a voltage drop and see the power as a waveform (undissipated). I know it sounds crazy but if you reread my posts (however piecemeal) they should convey my meaning fairly accurately.
woneill
Everything is achievable if we strive to get it.
I think I covered everybody (in the Mr. Grey Rollins style). For all the others not directly addressed, thanks for your interest in the theory and I hope it gives you something more than a headache🙂
gromanswe
Thank you for your welcome
woneill
I hate to think of myself as any kind of victum but some of the posts in this thread have made me feel like one. My fundamentals in the study of electronics may not match some of those in this forum but they are sound (pun intended). The THD numbers currently in use are based on fixed frequency inputs and as such are useless in predicting how well music will be represented IMHO. That is where the impetus for my quest of a new standard and measurement initiated.
mrfeedback
Yes, that is my point exactly but now I want to quantify it, prove it mathematically and ultimately create it as a standard to rate an amplifier/audio system. The Nania Audio Power Theory is a proposition on how we may identify what is causing the deterioration of the stereo image and to create a nomenclature that will help us identify the cause of the variations.
AudioFreak
When I used the example above I clearly stated that it was "for a given interval of a music signal" and for illustrative purposes and not a static measure but its nice to hear your laughter cease and your mind creak open. That goes for Duo and Helix as well.
Mr. Grey Rollins
Your suggestion indicates that you understand exactly what I am trying to do. In fact, I am currently compliling trigger profiles of those very differences. Unfortunately, they are still too random to form a concrete mathematical model but I think I will get there eventually. What I believe is key to the Nania Audio Power Theory is the premise that the amplitude and the frequency of the waveform sent is for the purposes of calculation pure power until it is distorted by the moving coils. In this way, the distortion can be measured by the variance of the correct "power profile" from the resultant power dissipated in the speaker.
Bill Fitzpatrick
As one the first people who saw a little sense in my idea, I owe you a thanks. That said, my idea will become clearer if you try to unlearn the idea that current is a result of a voltage drop and see the power as a waveform (undissipated). I know it sounds crazy but if you reread my posts (however piecemeal) they should convey my meaning fairly accurately.
woneill
Everything is achievable if we strive to get it.
I think I covered everybody (in the Mr. Grey Rollins style). For all the others not directly addressed, thanks for your interest in the theory and I hope it gives you something more than a headache🙂
Phase_Accurate
Why not?
This is a speaker design issue and is not what the theory is trying to identify. What I hope will eventually transpire from the Nania Audio Power Theory are tests that can quantifyably identify bad amp speaker combinations.
nania: You're not getting out of this one sooo quickly. We all know what you are talking about but the problem we've been really burning you for is the fact that you use very extreme figures and cases that wouldn't occur. Your original question that I answered was which amp delivered more current for the same signal, and simply stated, they will deliver the same current for a given frequency. if you happen to move both amps down a couple of octaves in frequency, the impedance will change, however, both amps will still have the exact same current loading even if one can't handle that amount of current, the speaker will still try to get the same amount of current flow for a similar voltage and frequency. But when you state another theory, please try to get some better numbers and description in there.
About THD figures, I too believe that the common distortion figure for a given frequency is crap. Therefore I like to measure my distortion by taking the average of all the different distortion levels over a frequency range between 20 and 20000 and average it out. I'll then go on to compare this with the distortions measured for small increments in frequency and draw a distortion plot which shows me how the amp acts. Of course, this plot must be redrawn for each different speaker. So, is this sort of what you were tring to get at???
About THD figures, I too believe that the common distortion figure for a given frequency is crap. Therefore I like to measure my distortion by taking the average of all the different distortion levels over a frequency range between 20 and 20000 and average it out. I'll then go on to compare this with the distortions measured for small increments in frequency and draw a distortion plot which shows me how the amp acts. Of course, this plot must be redrawn for each different speaker. So, is this sort of what you were tring to get at???
BTW nania: You can't compare voltage and current in a speaker the way you have since electricity simply doesn't work that way.
Voltage can't do something to a speaker while current does something different.
Also, most people already know how to find out if a speaker and amp combination is a bad one. It's very easy to tell with a few calculations and listening.
The only way you can get a speaker to move is to drop a voltage across it and cause current flow through the coil. Let me put this another way, amplifiers never ever send power to a speaker, the speaker draws it from the amplifier. Current simply has to flow through the coil to make it have a higher magnetic flux, nothing else does that.
Voltage can't do something to a speaker while current does something different.
Also, most people already know how to find out if a speaker and amp combination is a bad one. It's very easy to tell with a few calculations and listening.
The only way you can get a speaker to move is to drop a voltage across it and cause current flow through the coil. Let me put this another way, amplifiers never ever send power to a speaker, the speaker draws it from the amplifier. Current simply has to flow through the coil to make it have a higher magnetic flux, nothing else does that.
Duo,
Actually, it can! The reason you need to put a diode across the coil of a relay is so that when the voltage source is removed, the current, which could be said to have its own momentum, has somewhere to flow... Without the diode, the current flowing through the coil generates ITS OWN voltage drop across the terminals of the coil, in an attempt to continue flowing! These generated voltage drops can damage whatever components were used to resist the flow of the current.
Actually, the current doesn't have momentum in the classical sense, but while the current is flowing through the coil, it stores a level of energy as magnetic flux in the coil. It is the energy stored as flux that attempts to keep the current flowing.
Similarly, when first hit with a DC voltage source, a capacitor will have virtually no resistance to the flow of current. Theoretically, an infinite current could flow! However, over time, the same voltage source will have less and less ability to drive current through the device. With the original voltage source removed, the capacitor wants to drive the current back the way it came. Here this is a result of energy stored as electric fields, instead of magnetic flux.
Where I am going with this is that even for those courses that do deal with reactance, complex impedance and steady state AC behaviour of circuits, they often don't cover the practical issues and effects related to large signal effects, or the addition of dynamic transients.
Loudspeaker technology complicates this even further because here you have all of the above effects, and also the issue of energy transfers taking place through the mechanical movement of the speaker cone through a magnetic field.
All of this taken together presents the amplifier with a VERY complex and confusing interface to something that has a dynamically changing complex impedance, and will, at times, have its own built-in voltage source that can produce signal levels above the voltage driven by the amplifier!!!
This is not a simple exercise of applying V=IR!
Also as an aside, damping factor is a "small signal" measure of output resistance. What is often more important to output quality, and is handled by the transformer in the better Tube amps, is the ability of the amp to deliver MASSIVE current pulses for short durations while keeping the voltage the same. This is not a function of damping factor - this is a "large signal" transient capability, and is, in the end, in many semiconductor based amps, limited by the gain and the speed of the feedback circuits of the driver stage. The limits on this capability differentiate commercial amps from what they are trying to emulate: a pure voltage source...
Bill.
Actually, it can! The reason you need to put a diode across the coil of a relay is so that when the voltage source is removed, the current, which could be said to have its own momentum, has somewhere to flow... Without the diode, the current flowing through the coil generates ITS OWN voltage drop across the terminals of the coil, in an attempt to continue flowing! These generated voltage drops can damage whatever components were used to resist the flow of the current.
Actually, the current doesn't have momentum in the classical sense, but while the current is flowing through the coil, it stores a level of energy as magnetic flux in the coil. It is the energy stored as flux that attempts to keep the current flowing.
Similarly, when first hit with a DC voltage source, a capacitor will have virtually no resistance to the flow of current. Theoretically, an infinite current could flow! However, over time, the same voltage source will have less and less ability to drive current through the device. With the original voltage source removed, the capacitor wants to drive the current back the way it came. Here this is a result of energy stored as electric fields, instead of magnetic flux.
Where I am going with this is that even for those courses that do deal with reactance, complex impedance and steady state AC behaviour of circuits, they often don't cover the practical issues and effects related to large signal effects, or the addition of dynamic transients.
Loudspeaker technology complicates this even further because here you have all of the above effects, and also the issue of energy transfers taking place through the mechanical movement of the speaker cone through a magnetic field.
All of this taken together presents the amplifier with a VERY complex and confusing interface to something that has a dynamically changing complex impedance, and will, at times, have its own built-in voltage source that can produce signal levels above the voltage driven by the amplifier!!!
This is not a simple exercise of applying V=IR!
Also as an aside, damping factor is a "small signal" measure of output resistance. What is often more important to output quality, and is handled by the transformer in the better Tube amps, is the ability of the amp to deliver MASSIVE current pulses for short durations while keeping the voltage the same. This is not a function of damping factor - this is a "large signal" transient capability, and is, in the end, in many semiconductor based amps, limited by the gain and the speed of the feedback circuits of the driver stage. The limits on this capability differentiate commercial amps from what they are trying to emulate: a pure voltage source...
Bill.
Nania:
Actually I can see the power as a waveform.
I see the voltage waveform at the amp terminals which is supposed to represent the true signal.
I see the current waveform which DOES NOT look like the voltage waveform. Taking descriptive liberties, you COULD say that the current waveform is distorted.
It follows then that the power waveform doesn't look like either. Taking the same liberties, you COULD say that the power waveform is distorted.
I have no problems with those observations but they are nothing new.
On the other hand . . .
Suppose you took a series RL network and a series RC network (with matching F3s), paralleled them and called it a DUT (Device Under Test). The current waveform through the DUT will now look like the voltage wave form applied to the DUT. The power waveform now also looks like the voltage waveform. The DUT is somewhat representative the ELECTRICAL nature of a simple 2 way speaker. Replacing the resistors in the DUT with actual speakers changes things of course because other factors enter the picture. It is the job of a speaker designer to reduce the effects of these other factors to a negligible level, preferably to zero.
But I'm sure you already know this. Again, nothing new here.
So you want a mathematical description of this DUT speaker with all of it's flaws and you want to match it to an amp having inverse or complementary mathematical characteristics?
I don't think this going to happen because the closer an amp gets to being perfect the more its mathematical description reduces to zero. As it is, well designed amps begin to approach the zero description anyway.
I think you may be barking up the wrong tree. Now if you could get the ACOUSTIC output of a speaker system into a feedback (whoops, I said a naughty word) loop you might have something.
More dialog, please.
Actually I can see the power as a waveform.
I see the voltage waveform at the amp terminals which is supposed to represent the true signal.
I see the current waveform which DOES NOT look like the voltage waveform. Taking descriptive liberties, you COULD say that the current waveform is distorted.
It follows then that the power waveform doesn't look like either. Taking the same liberties, you COULD say that the power waveform is distorted.
I have no problems with those observations but they are nothing new.
On the other hand . . .
Suppose you took a series RL network and a series RC network (with matching F3s), paralleled them and called it a DUT (Device Under Test). The current waveform through the DUT will now look like the voltage wave form applied to the DUT. The power waveform now also looks like the voltage waveform. The DUT is somewhat representative the ELECTRICAL nature of a simple 2 way speaker. Replacing the resistors in the DUT with actual speakers changes things of course because other factors enter the picture. It is the job of a speaker designer to reduce the effects of these other factors to a negligible level, preferably to zero.
But I'm sure you already know this. Again, nothing new here.
So you want a mathematical description of this DUT speaker with all of it's flaws and you want to match it to an amp having inverse or complementary mathematical characteristics?
I don't think this going to happen because the closer an amp gets to being perfect the more its mathematical description reduces to zero. As it is, well designed amps begin to approach the zero description anyway.
I think you may be barking up the wrong tree. Now if you could get the ACOUSTIC output of a speaker system into a feedback (whoops, I said a naughty word) loop you might have something.
More dialog, please.
Hi Nania
The reason why current drive can't be regarded as a continuous grip on the voicecoil and voltage drive as hitting the voicecoil is:
1.) BOTH are continuous-time processes.
2.) Current and voltage are both strongly related to each other, described by a differential equation. In case of a purely resistive load this would simply be Ohm's law (also in case of a real loudspeaker for a steady state signal, i.e. DC current/voltage).
In fact the only difference is that for current-drive the amplifier output voltage is defined by the load current and the load while for voltage drive the load current is defined by the output voltage and the load.
In an ordinary driver using the electromagnetic conversion principle the damping of it's fundamental resonance is mainly performed by the electromagnetic conversion process (and the amp's low output impedance). It isn't possible to make a driver using this working principle that doesn't have any cone -mass and -compliance related mechanical resonance. Period.
If you tried to achieve damping purely mechanically then the efficiency of the driver would definitely suffer.
As already mentioned before, current-drive can achieve better performance for frequencies well above the driver's fundamental resonance (THD, frequency response and temporal behaviour) but it isn't a cure-all.
Regards
Charles
The reason why current drive can't be regarded as a continuous grip on the voicecoil and voltage drive as hitting the voicecoil is:
1.) BOTH are continuous-time processes.
2.) Current and voltage are both strongly related to each other, described by a differential equation. In case of a purely resistive load this would simply be Ohm's law (also in case of a real loudspeaker for a steady state signal, i.e. DC current/voltage).
In fact the only difference is that for current-drive the amplifier output voltage is defined by the load current and the load while for voltage drive the load current is defined by the output voltage and the load.
In an ordinary driver using the electromagnetic conversion principle the damping of it's fundamental resonance is mainly performed by the electromagnetic conversion process (and the amp's low output impedance). It isn't possible to make a driver using this working principle that doesn't have any cone -mass and -compliance related mechanical resonance. Period.
If you tried to achieve damping purely mechanically then the efficiency of the driver would definitely suffer.
As already mentioned before, current-drive can achieve better performance for frequencies well above the driver's fundamental resonance (THD, frequency response and temporal behaviour) but it isn't a cure-all.
Regards
Charles
Hello Charles, if using current drive, what happens if the driver resonance is damped by a shunt RLC series network ?.
Regards, Eric.
Regards, Eric.
woneill: You probably haven't read the bit that nania noted about feeding 8mv at 2 amps or 2mv at 8 amps into a speaker. This wouldn't work since the voltage drop accross the speaker determines the current flow. If his statment about this were true, then a speaker would have to change impedance to the reciprocal of the original specification. That is impossible for for more than a few nanoseconds. I know how relays work with semiconductors and I know that it's customary to insert a diode to prevent failure, this can also be done in audio amplifiers, but I wasn't talking about back emf.
G'day Eric
At a first glimpse this looks inviting (apart from the power loss, but this happens of course as well if such a network is used simply for impedance correction).
I think the dampig of the driver's resonance would basically work that way and there might even be some possibility to influence the TS parameters electronically as with the ACE-bass method.
But for mid to high frequencies this parallel network would have influence on the voltage/current relation at the outputput of the amp as well deteriorating the positive effect of current drive (it's series resistor has to be smaller than Rdc of the voice-coil).
There was once an article in "Electronics World" written by John Watkinson describing the pros and cons of current drive. Maybe I can dig it out and see what he was suggesting to overcome the damping problem. But as far as I remember he suggested some kind of frequency-dependant current-feedback (I kindly apologize for uttering this forum's most obscene expression).
Regards
Charles
At a first glimpse this looks inviting (apart from the power loss, but this happens of course as well if such a network is used simply for impedance correction).
I think the dampig of the driver's resonance would basically work that way and there might even be some possibility to influence the TS parameters electronically as with the ACE-bass method.
But for mid to high frequencies this parallel network would have influence on the voltage/current relation at the outputput of the amp as well deteriorating the positive effect of current drive (it's series resistor has to be smaller than Rdc of the voice-coil).
There was once an article in "Electronics World" written by John Watkinson describing the pros and cons of current drive. Maybe I can dig it out and see what he was suggesting to overcome the damping problem. But as far as I remember he suggested some kind of frequency-dependant current-feedback (I kindly apologize for uttering this forum's most obscene expression).
Regards
Charles
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