I have seen a voice coil short. It happens where the wires exit the coil. Most likely on the cheap drivers you would never use in a stadium. It's the primary cause of drivers catching fire..
Also a drivers impedance can change with the location shift of the voice coil in the gap.
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I'm sorry Ed you're wrong again on some very basic stuff, as usual let's just drop it you have no interest in questioning your misconceptions.
Will you folks PLEASE stop misusing the concept of impedance. As Heavyside defined it the term ONLY applies to the sinusoidal steady state. The instantaneous voltage and current might interest you but it has nothing to do with impedance. The concept applies to the response to one input stimulus all other inputs at zero.
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Scott
A few things have been added since then. Among other things the use of complex numbers to describe it. But since we are talking about loudspeaker impedance I think everyone here is clear on what we mean.
But just to satisfy you, give me a year or two and I will get the definition spelled out in the standards.
A few things have been added since then. Among other things the use of complex numbers to describe it. But since we are talking about loudspeaker impedance I think everyone here is clear on what we mean.
But just to satisfy you, give me a year or two and I will get the definition spelled out in the standards.
Really, Heavyside had no clue about complex numbers? I think you're missing something. We're a year or two away from grasping these concepts what a laugh.
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Actually depending on mounting as in a ceiling loudspeaker the coil can move with time and even in some conditions HVAC operation.
That would even change the static impedance.
But what would you call the change to impedance from voice coil heating during use?
Demian
We do see occasional woofer shorts when the terminal to cone leads are too long and dressed incorrectly. That is a production or repair test so it shouldn't show up in the field. As to causing fires, if it is a paper voice coil form I have no problems setting those on fire!
Scott
From Wiki
"The term impedance was coined by Oliver Heaviside in July 1886.[1][2] Arthur Kennelly was the first to represent impedance with complex numbers in 1893.[3]"
And as usual we really aren't communicating. I will get the paperwork started to make sure loudspeaker impedance is defined in the standards that define how a loudspeaker is specified. Right now it includes some other items that vary from your understanding of electrical impedance vs loudspeaker impedance.
RF can damage the blood brain barrier even at low levels. Just because there's nutters all over it doesn't mean it's wrong. Here's a neurosurgeon with some amygdalas:
https://youtu.be/E_WJ_aJPWIA?t=280
https://youtu.be/E_WJ_aJPWIA?t=280
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The term "imaginary" for these quantities was coined by René Descartes in 1637. You are weak ground, why do you bother?
A now retired broadcast radio transmitter technician friend is very vocal on keeping mobile phones distant from the body/head.
His recommendation is to use BT headsets or hands free.
He also maintains that fish/steak can be cooked in a MWO by repeated short bursts, even though the exposures and repetition rate are insufficient to raise the temperature.
I have not confirmed this experiment, but it is alarming if true.
Dan.
Work in this field is pretty darn contentious, and, at most, it's going to be very low level and have subtle long-term effects. CSF is quite conductive, so penetration depths are going to be low. Primarily, we're talking a small bit of loss that causes local heating. Yes, the blood-brain barrier is pretty delicate and there's still tons to learn about how it becomes permeabilized, but the as-described "EM sensitivity" really lacks scientific foundation. Please understand that's a far cry from being sympathetic to those who have nonspecific maladies which they ascribe *to* EM sensitivity.
Altogether, I'm not saying that EM radiation has zero biological effect, but minimal and very subtle. There might be a RF-coupling or localized heating into RNA complexes (most likely to be affected as they're not as stable as most anything else) and change the local reaction kinetics just enough to move the equilibrium and, ultimately expression. This would most likely manifest in the epigenome.
The types of complaints being leveled here are going to be *quite* a few dB less likely than anything coming off your cell phone, too. Mind your Poynting vectors.
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Max
To make a short story long:
One if my aunts recipe for cooking hamburgers is to put the patties on the grill at low heat until the juices all rise to the top. They then get turned over and when there is no juice left they are done.
When I am cooking burgers and she and hers are dining I cook my burgers quickly on high heat until the center just gets warm. But to be the good host I take the burgers for her family and then use the microwave oven on them for another two minutes at full power to make sure the patties are juiceless and gray all the way through. Her family apparently likes this extra step as they actually eat them and go for second helpings.
Now from usage the microwave oven in the reduced power mode does use pulse width modulation. So at the lowest setting it is only on 10% of the time. When hamburger is heated this way it still changes color and takes almost as much energy to heat to the same lump of almost coal my aunt likes.
Now as to the effect of low level RFI some friends actually were using specific frequencies to cause organic molecules to rotate enhancing the ability to separate then. They believed that the energy radiated by then common VGA monitors were well tuned to have the same effect on parts of human brains.
But they never went so far as to worry about permanent damage.
To make a short story long:
One if my aunts recipe for cooking hamburgers is to put the patties on the grill at low heat until the juices all rise to the top. They then get turned over and when there is no juice left they are done.
When I am cooking burgers and she and hers are dining I cook my burgers quickly on high heat until the center just gets warm. But to be the good host I take the burgers for her family and then use the microwave oven on them for another two minutes at full power to make sure the patties are juiceless and gray all the way through. Her family apparently likes this extra step as they actually eat them and go for second helpings.
Now from usage the microwave oven in the reduced power mode does use pulse width modulation. So at the lowest setting it is only on 10% of the time. When hamburger is heated this way it still changes color and takes almost as much energy to heat to the same lump of almost coal my aunt likes.
Now as to the effect of low level RFI some friends actually were using specific frequencies to cause organic molecules to rotate enhancing the ability to separate then. They believed that the energy radiated by then common VGA monitors were well tuned to have the same effect on parts of human brains.
But they never went so far as to worry about permanent damage.
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Ditto for steaks....cook on highish heat until top side oozing blood and gets warm to the touch, flip for a minute and your done.
My friend was suggesting duty cycle rather lower than 10% and not enough to cause warming.
Dan.
So use BT where the transmitter is closer to you head?
You can cook salmon in lemon juice, doesn't mean lemons cause cancer!
I do feel for people for whom the presence of a transmission sauce causes headaches etc. I fear in many cases if offered a cure they would not accept it.
That too, but even normal signal sources can sometimes produce madness in amps. Whis is always a function of a large program peak and a nasty reactive speaker. Hence our real world ned for hefty power supplies.
The guy who sold me my H/K P-2400 phoned up the other day and tried to buy it back. He listens to a pair of AR3a Improved speakers, still with their original caps inside. He told me ha could not find another power amp which could drive them as neatly as the H/K, including models from Luxman, Denon and such like, no cheap powerhouses but relatively quality products. My conscience is clear - I asked him twice before selling it to me was he sure he wanted to do that, and both times he said yes. Since he has no money shortage, I told him to look up Parasound, based on only one personal experience I have with your model 1205.
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