I believe you have no idea what you are talking about. (cent 1)
I also believe that never stopped you from criticizing others. (cent 2)
my two cents.
jn
to JC: No, please do not be misleading (intentionally????). Most of us know for long what is the difference between voltage and current drive and that there might be some distortion reduction with current drive that is accompanied by frequency equalization. Joe is criticized for promotion of impedance flattening as a way to distortion reduction with voltage drive. I would have hoped you were able to understand the point. However, I am gradually loosing my hopes.
John do not sully the DOE research labs with that BS. It's an insult to present and past employees
PMA: if you notice, John's strategy is to cheerlead anyone finds themselves in conflict with a members/ideologies he doesn't like. He never provides a lick of relevant content to these discussions, and I genuinely doubt he reads carefully to what is actually being discussed. There's no getting him to understand a technical point, he's not even listening to anything that doesn't further his position as a rejected genius.
PMA: if you notice, John's strategy is to cheerlead anyone finds themselves in conflict with a members/ideologies he doesn't like. He never provides a lick of relevant content to these discussions, and I genuinely doubt he reads carefully to what is actually being discussed. There's no getting him to understand a technical point, he's not even listening to anything that doesn't further his position as a rejected genius.
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Yes Scott I understand it quite well, and also the concept promotion. I would have hoped that it would not be so easily swallowed by some. Since I joined the forum in 2002, I had to make some corrections about those I had considered as "authorities" in the field.
I agree that I do not know whether Joe is giving us something useful in a general way, but it might well work for a specific loudspeaker design.
We are pretty stuck with voltage drive in amps, except for servo amps. When I designed servo amps for motor drives, back 50 years ago, we preferred current drive over voltage drive. The only reason to specify voltage drive conditions is the amount of voltage swing necessary to achieve a maximum SPEED. If you have too much back EMF, then even current drive will not make the motor go faster.
I had this problem in 1968 with a capstan servo drive for a pro analog tape recorder. I realized that a few volts more added to the DC power supply would give us 30ips capability. My boss nixed the idea, thinking that 30ips would never be revived. He was wrong of course, and 10 years later, 30ips came back strong for mastering. Many engineers cannot imagine the future, or even care about improving things beyond the minimum specified. That is why they never do anything significant.
Apparently, the early work with direct radiators had to include the source resistance of the amp and added it in series with the voice coil resistance to get proper calculations. As the decades progressed, this series resistance has diminished to something almost trivial.
That is the damping factor (overstatement) and how DF over 20 or so into the lowest impedance of the speaker being driven probably does not mean much, and most solid state amps have a relatively low drive impedance and a relatively high DF.
Much of what is being said here is just Sophomoric posturing, and is actually more confusing than enlightening. What is the point?
We are pretty stuck with voltage drive in amps, except for servo amps. When I designed servo amps for motor drives, back 50 years ago, we preferred current drive over voltage drive. The only reason to specify voltage drive conditions is the amount of voltage swing necessary to achieve a maximum SPEED. If you have too much back EMF, then even current drive will not make the motor go faster.
I had this problem in 1968 with a capstan servo drive for a pro analog tape recorder. I realized that a few volts more added to the DC power supply would give us 30ips capability. My boss nixed the idea, thinking that 30ips would never be revived. He was wrong of course, and 10 years later, 30ips came back strong for mastering. Many engineers cannot imagine the future, or even care about improving things beyond the minimum specified. That is why they never do anything significant.
Apparently, the early work with direct radiators had to include the source resistance of the amp and added it in series with the voice coil resistance to get proper calculations. As the decades progressed, this series resistance has diminished to something almost trivial.
That is the damping factor (overstatement) and how DF over 20 or so into the lowest impedance of the speaker being driven probably does not mean much, and most solid state amps have a relatively low drive impedance and a relatively high DF.
Much of what is being said here is just Sophomoric posturing, and is actually more confusing than enlightening. What is the point?
You still do not understand the concept. He thinks the amp needs it to lower distortion.
As a person with 25 plus years actually working with every motor type imaginable, that is the weirdest and totally misapplied statement I can imagine.
You should have said..."If you have too much back EMF, you will exceed the rail voltage of the controller, and that will limit your top speed.
Or: "all DC motors have a specific volts per KRPM factor listed on the nameplate. By simple multiplication, you can determine the maximum output voltage required for the desired speed. If the speed times the factor exceeds the rail voltage (minus pass element drop), you will not reach the desired speed.
Wow, you have a thing for dissing engineers. You should replace "engineer" with "human".
jn
Yes the amplifier's THD is much lower than that of the speaker, but that doesn't necessarily mean the amplifier's contribution to the distortion can't be heard. See my rant of this here in recent weeks. everyone "knows" this about THD (how one can hear most SS electronic distortion through speakers that make their own distortion that measures much higher by THD), but then it gets ignored.
Still, adding the resistor to "flatten" the impedance may not significantly change the amplifier distortion (amplifier distortion does tend to go up when driving a lower impedance, but usually not by a lot).
If I wanted to be obsessive (and I'm tempted to be), I'd ask what model amplifier and speaker cable you used, especially the <strike>damping factor</strike> amplifier's output impedance, and at least the speaker cable's DC resistance, and also its capacitance (across conductors, no connection on the far end) and inductance (shorted on the far end).
ETA: Not meaning to be overcritial or anything, thanks for the work.
Well JN as a 'coil winder' for your company, you might have more experience with servos, especially in recent years than I have had, since I did my last, 50 years ago. But, I was guided by my mentors to use current drive, not voltage drive for servos, because it removed inductance from limiting the correction and reduced the drive parameters to mostly torque, as I recall. I am fairly sure that you did not design servo amplifiers, like I did, you simply do not know enough about amp design, it would seem.
As far as speaker drive is concerned, it appears that the direct radiator was designed with voltage drive in mind, in order to compensate for the bass resonance and actually reduce the current near resonance to flatten the response. It is also a fact that voltage drive will be affected by the voice coil inductance and limit the high frequency bandwidth as well. That is why Joe's V vs I speaker output graph makes sense to me.
It has been known for the last 100 years or more that current drive drives loudspeakers in a certain way. Sometimes this might have been an advantage, often it was not, and the direct radiator design, starting in 1925 also included the fact that the voltage drive will be diluted into something different just by the series resistance of the voice coil. It would appear that loudspeakers are almost always optimized with voltage drive as the source, whatever the parameters are. I recommend to everyone to read up on speaker models and parameters. I think the Klippel group has more info than anybody, but they are sort of an advanced course, first things first.
As far as speaker drive is concerned, it appears that the direct radiator was designed with voltage drive in mind, in order to compensate for the bass resonance and actually reduce the current near resonance to flatten the response. It is also a fact that voltage drive will be affected by the voice coil inductance and limit the high frequency bandwidth as well. That is why Joe's V vs I speaker output graph makes sense to me.
It has been known for the last 100 years or more that current drive drives loudspeakers in a certain way. Sometimes this might have been an advantage, often it was not, and the direct radiator design, starting in 1925 also included the fact that the voltage drive will be diluted into something different just by the series resistance of the voice coil. It would appear that loudspeakers are almost always optimized with voltage drive as the source, whatever the parameters are. I recommend to everyone to read up on speaker models and parameters. I think the Klippel group has more info than anybody, but they are sort of an advanced course, first things first.
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You have no idea what my areas of expertise are. All you know is that the website has my write-ups for specific superconducting magnets that I wound using my 11 axis ultrasonic welding machine. The site lists none of my other skills, none of my other talents. Now, I'm working DC brush, DC brushless, 3 phase brushless servo's, solenoids, all under heavy PID based motion control for positioning to the tune of 5 nanometer precision on multiton objects. (oh, and I'm still winding coils...
) My current windmill as it were, it that the motion control people are not taught bode plots, gain margin, nor phase margin despite it being a negative feedback positioning loop. So I cannot even start to teach them any thing about adaptive tuning for accuracy despite heavily non linear forces vs position.Not a problem. You say "but" as if you are defending something, but those techniques and your work did not require defending. Nowadays, most DC brush servos will have a second tachometer winding for velocity feedback, that can be used as the differential input of the PID. Other controllers calculate a running velocity from the encoder, use that for the differential feedback component.
I am very good with many of the components, specifically thermal, failure analysis, that kind of stuff. But you do not have to be "fairly sure" about my experience designing amplifiers, be confident. I look to all you guys for that and have no issue with stating many here are well above me, yourself included..
That is why I recommended Klippel to you as more modern, and ESA's stuff on current drive as he is an excellent source for magnetic understandings.
Klippel's Le(i) writeups are not quite accurate, and the presentation can be very misleading.
jn
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Hi John,
I think you are making assumptions in only one direction, and doing a great disservice to those among us who know exactly what they are doing. This of course is not new, I just wish you would consider what you are going to post before you do.
John, by commenting on things you haven't seen the way you are makes you look a little silly. Your career was built on a solid understanding of electronics. Now you are following blind with a religious fervor.
-Chris
I think you are making assumptions in only one direction, and doing a great disservice to those among us who know exactly what they are doing. This of course is not new, I just wish you would consider what you are going to post before you do.
Doesn't even need a comment. Mr. Bybee is a big secret, as is everything he works on.
John, by commenting on things you haven't seen the way you are makes you look a little silly. Your career was built on a solid understanding of electronics. Now you are following blind with a religious fervor.
-Chris
If Joe's claim has really related with reduced speaker distortion, then that is the mistake. I have mentioned that there is something that is audible and can usually be perceived as distortion, but it is not really a distortion in normal sense (amp's THD). It is highly related with the use of negative feedback in amplifiers and the use of multi drivers (which calls for crossover) in speakers. Good luck with your obsessions!
Maybe this is the right time for a reminder of Clarke's three laws:
- When a distinguished but elderly scientist states that something is possible, he is almost certainly right. When he states that something is impossible, he is very probably wrong.
- The only way of discovering the limits of the possible is to venture a little way past them into the impossible.
- Any sufficiently advanced technology is indistinguishable from magic.
How about promoting potentially deadly (if it works as advertised) device that affect change in polarity of all electron and proton in close proximity? As known to physics, a flip in polarity of any lepton and hadron will form antimatter.
Can not say it better.
As I know it, there is nothing really 'rocket science' advanced technology involved. But the usual processes are very old where in the past human in average didn't have yet high expectation about sound quality compared to today (they had false euphoria regarding advancement in solid state). There is no new Physics here, only a mechanism that people are unaware that it is audible. The Physics is quite simple, such that audio world might know it in the future, but the chance is also small because competent engineers tend to be skeptical about audibility of things. Experiment without knowing the mechanism is difficult (i.e. measuring the wrong thing).
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