Just thinking about it, the voltage across that resistor represents the current the speaker is "requesting" to keep up with the voltage of the amp. That involves the moving mass as well as any nonlinear force errors. Voltage feedback is only what the amp is requesting the speaker do w/r to velocity.
jn
jn
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Sometimes it helps to set ( change) the series resistance a bit compared to pure Re of the voice coil. Modifies Q as well.
JN
What a shortening ring does is to limit flux modulation by forming a low resistance secondary on the transformer formed by pole piece and VC. Which would otherwise not be a transformer but a coil with a solid iron core.
Eddy currents in the shortening ring are not the operating principle. It is the shorted secondary of a xfrmer which increases the conductance. And keeps the magnetic field in the air gap more constant as a result.
What a shortening ring does is to limit flux modulation by forming a low resistance secondary on the transformer formed by pole piece and VC. Which would otherwise not be a transformer but a coil with a solid iron core.
Eddy currents in the shortening ring are not the operating principle. It is the shorted secondary of a xfrmer which increases the conductance. And keeps the magnetic field in the air gap more constant as a result.
We are both saying almost the exact same thing. Eddy currents are defined as currents which circulate around the flux lines caused by a time varying magnetic field. Most people think only of eddies as being in solid surfaces, but they are still called that if that surface has a hole through it. So the mechanisms are the same. (This is why the NEC requires high current three phase AC conductors all go through the same penetration hole in large equipment. If you put each phase through their own hole, the metal at the penetration tends to start glowing orange...at least until the explosion.)
The shorting rings create an opposing magnetic field because the currents within the ring are 90 degrees lagging the vc magnetic field, and the ring currents generate a magfield which is another ninety degrees back.
This is the exact same mechanism responsible for trying to shield cables with the coaxial shield when a loop of signal is formed. The shield currents caused by loop trapped magnetic change make a magfield 180 degrees out of the forcing magfield, so it is trying to cancel out the magfield trapped in the loop.
Using different correct terminology btw, is not wrong, your explanation is indeed correct. But we are saying the same thing.
jn
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Exactly.
Or, the current induced in the shorting ring opposes any magnetic flux modulation in the core.
Eddy currents in the pole piece are a separate issue.
ATC have a white paper on it. I'll dig it up later.
T
The currents in the ring create magfield which opposes the vc magfield. That exclusion reduces the inductance.
Eddy currents in the pole piece also tries to exclude time varying vc flux.
Same with the front plate.
That is why we use laminations for all of our magnets. Only the very high slew rate magnets require ferrite. We get around the lower permeability by simply raising the voltage and currents. 10 to 30 kV pulsers with 5 to 30 kiloamp pulses ain't no big deal..
I tried to find an ATC writeup, to no avail..I look forward to the link if you do find it.
jn
Eddy currents in the pole piece also tries to exclude time varying vc flux.
Same with the front plate.
That is why we use laminations for all of our magnets. Only the very high slew rate magnets require ferrite. We get around the lower permeability by simply raising the voltage and currents. 10 to 30 kV pulsers with 5 to 30 kiloamp pulses ain't no big deal..
I tried to find an ATC writeup, to no avail..I look forward to the link if you do find it.
jn
Joe has repeatedly told us that his impedance-controlled speaker is so good that the output impedance of the amp+cable is irrelevant, hence an imperfect voltage source should be as good as a perfect voltage source. Basically he is confused, and he is so confused that he has no idea just how confused he is.Zung said:
He has gotten better, he once simply called the magnitude of the speaker impedance a DC resistance.
As for the amp/cable/speaker swapping, if the frequency response and supposed distortion effects are not separated this is just some random exercise yielding no useful information.
I'm having a little trouble opening attachments on this device, but I suspect it would be tricky to implement on my system, see schematic on this page Pluto electronics
I'm also not worried about long speaker cables, they are less than a meter and of course separate for woofer and tweeter because bi-amped.
Yes, but those are required only in the specific case when load has to be ground-referenced or is used as a bridge-tied load. In the end it's just the sense resistor's voltage drop measured differentially vs. single-ended.
50 years I built a floating current source using both positive and negative with a balanced bridge amplifier while employed at Ampex Research that put out 50A and 50V. It was more complex than most motor drive amps, but I was looking to make the balanced bridge also as a floating voltage source for hi fi amps in the future. It, of course, needed air blown heatsinks and a big power supply.
No folks, I am not a loudspeaker expert, and I wish one was here to keep the debate to a minimum. That is why I go back to the classic texts by Olsen et al. I wish everybody did.
No folks, I am not a loudspeaker expert, and I wish one was here to keep the debate to a minimum. That is why I go back to the classic texts by Olsen et al. I wish everybody did.
A small correction, his name is Harry F. Olson and should be spelled properly, he deserves it. His texts are classics, however a lot of water flew in Kamo river since that time.
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