Lenz's Law in action

[ack]

We have talked about Lenz's Law a number of times in the past, with respect to a cartridge's coil/magnet interaction (the generated current by the coil will create a magnetic field opposing the magnet, thus affecting cantilever movement ever so slightly; this is more severe as you lower the loading value == more current; see also http://www.whatsbestforum.com/showthread.php?3468-Ortofon-A90&p=81833&viewfull=1#post81833).

Here's the law in action, albeit at a much larger scale, showing how a magnet moving through a copper tube is slowed down by this force

 

[jeromelang]

Metallic platter directly underneath a cartridge changes its sound.

Soundstage will be smaller than what the whole turntable assembly should be capable of.
Timbre accquires an harder edge.
Bass "thump" is accentuated.

That's Lenz's law too.


Even if that metallic platter is non-magnetic, the cartridge's magnetic field will still induce a current flow within the metallic platter, leading to an opposing magnetic field being created that in turn alter the cartridge's intrinsic magnetic field - thereby affecting its sound.

 

[ack]

Yes, a metallic platter is theoretically capable of changing the cartridge's magnetic flux, but I don't know to what degree. For example, there are other videos on the same theme like the one below, comparing a magnet falling through copper tubes against aluminum and other materials - clearly, aluminum can still have an effect. By inference, it would seem that copper, aluminum, various magnetic steel alloys, et al ought to have some sort of effect to varying degrees, but I don't personally have any quantifiable data. But I can tell you, this was one of the reasons I have stuck with an acrylic platter. At the same time, one can argue that the magnetic interference might be so small that the LP itself lifts the cartridge far enough as to have no effect... don't know.

 

[FrantzM]

Metallic platter directly underneath a cartridge changes its sound.

Soundstage will be smaller than what the whole turntable assembly should be capable of.
Timbre accquires an harder edge.
Bass "thump" is accentuated.

That's Lenz's law too.


Even if that metallic platter is non-magnetic, the cartridge's magnetic field will still induce a current flow within the metallic platter, leading to an opposing magnetic field being created that in turn alter the cartridge's intrinsic magnetic field - thereby affecting its sound.

Since we are in Science here ... That it affects it , no doubt, that you really hear it .. some doubt. The simple of fact of knowing creates the bias. From that point one may hear things. Reliability of the perception has to be questionned.

 

[microstrip]

Since we are in Science here ... That it affects it , no doubt, that you really hear it .. some doubt. The simple of fact of knowing creates the bias. From that point one may hear things. Reliability of the perception has to be questionned.

Everyone can question the reliability of the perception - it is a common audiophile subject, almost childishly addressed, plenty of anecdotal immediate examples and jokes. Naturally people run away from the reliability of the "non perception", the so called positive tests, a much more challenging subject.

Considering pure science, even the example given is excellent to show how complex can be a very simple situation. The moving coil EMF is due to Faraday's Law, Lenz law gives an immediate and misleading explanation of cartridge resistive damping ...

 

[FrantzM]

Everyone can question the reliability of the perception - it is a common audiophile subject, almost childishly addressed, plenty of anecdotal immediate examples and jokes. Naturally people run away from the reliability of the "non perception", the so called positive tests, a much more challenging subject.

Considering pure science, even the example given is excellent to show how complex can be a very simple situation. The moving coil EMF is due to Faraday's Law, Lenz law gives an immediate and misleading explanation of cartridge resistive damping ...

What point did you want to address that our perception is unreliable? THat I said so? Those are facts.

Can you confirm as a fact his perception? please by all means do. Or yours for that matter.

 

[microstrip]

What point did you want to address that our perception is unreliable? THat I said so? Those are facts.

Can you confirm as a fact his perception? please by all means do. Or yours for that matter.

My comment was triggered by your introduction - Since we are in Science here and then just adding a commonly known and reported fact, fully ignoring the hard science part. Most probably people will easily ear effects due to different platter materials due to the mechanical characteristics - it is known since long that they are above reliable audibility thresholds.

However "Lenz science" will prove that due to the steady magnetic condition of the platter - when rotating a non magnetized platter with cylindrical symmetry will keep always the same equivalent position relative to the stylus - there will be no change in the EMF generated or force applied to the cartridge. It is like dropping the magnet in a longitudinally slotted tube.

Magnetic platters will simply change tracking force, with harmonic non linear dependencies on position.

Curiously the original Ack post link has a warning that has been ignored - Unfortunately there seems to be no concensus on how significant the effect of stylus damping is, or even whether or not stylus damping is a good or bad thing.

Pseudo science - that in audio usually takes the nice name of non quantified - is a dangerous game. Usually it picks a small effect in the middle of an ignored large effect and tries to justify the differences with the small effect.

 

[YashN]

We have talked about Lenz's Law a number of times in the past, with respect to a cartridge's coil/magnet interaction (the generated current by the coil will create a magnetic field opposing the magnet, thus affecting cantilever movement ever so slightly; this is more severe as you lower the loading value == more current

Interesting. I know of a way to mitigate that effect. Never thought of its application at that area though, will keep it at the back of my mind, maybe one day I'll get to experiment with this if things aren't too small that is.

 

[awsmone]

Metallic platter directly underneath a cartridge changes its sound.

Soundstage will be smaller than what the whole turntable assembly should be capable of.
Timbre accquires an harder edge.
Bass "thump" is accentuated.

That's Lenz's law too.


Even if that metallic platter is non-magnetic, the cartridge's magnetic field will still induce a current flow within the metallic platter, leading to an opposing magnetic field being created that in turn alter the cartridge's intrinsic magnetic field - thereby affecting its sound.

Metallic platter directly underneath a cartridge changes its

Are you referring to

Ferromagnetism.... iron was used in some old platters eg thorens 124 mk1

Paramagnetism......aluminium and magnesium are used in platters same direction as magnetic field

Diamagnetism.......carbon and copper though very weak effect opposite direction to magnetic field

 

[FrantzM]

Since we are in Science here ... That it affects it , no doubt, that you really hear it .. some doubt. The simple of fact of knowing creates the bias. From that point one may hear things. Reliability of the perception has to be questionned.

My comment was triggered by your introduction - Since we are in Science here and then just adding a commonly known and reported fact, fully ignoring the hard science part. Most probably people will easily ear effects due to different platter materials due to the mechanical characteristics - it is known since long that they are above reliable audibility thresholds.

However "Lenz science" will prove that due to the steady magnetic condition of the platter - when rotating a non magnetized platter with cylindrical symmetry will keep always the same equivalent position relative to the stylus - there will be no change in the EMF generated or force applied to the cartridge. It is like dropping the magnet in a longitudinally slotted tube.

Magnetic platters will simply change tracking force, with harmonic non linear dependencies on position.

Curiously the original Ack post link has a warning that has been ignored - Unfortunately there seems to be no concensus on how significant the effect of stylus damping is, or even whether or not stylus damping is a good or bad thing.

Pseudo science - that in audio usually takes the nice name of non quantified - is a dangerous game. Usually it picks a small effect in the middle of an ignored large effect and tries to justify the differences with the small effect.

Thank you for the masterly explanation. Am I allowed to question the audibility of the effects?

 

[awsmone]

My comment was triggered by your introduction - Since we are in Science here and then just adding a commonly known and reported fact, fully ignoring the hard science part. Most probably people will easily ear effects due to different platter materials due to the mechanical characteristics - it is known since long that they are above reliable audibility thresholds.

However "Lenz science" will prove that due to the steady magnetic condition of the platter - when rotating a non magnetized platter with cylindrical symmetry will keep always the same equivalent position relative to the stylus - there will be no change in the EMF generated or force applied to the cartridge. It is like dropping the magnet in a longitudinally slotted tube.

Magnetic platters will simply change tracking force, with harmonic non linear dependencies on position.

Curiously the original Ack post link has a warning that has been ignored - Unfortunately there seems to be no concensus on how significant the effect of stylus damping is, or even whether or not stylus damping is a good or bad thing.

Pseudo science - that in audio usually takes the nice name of non quantified - is a dangerous game. Usually it picks a small effect in the middle of an ignored large effect and tries to justify the differences with the small effect.

Its actually an interesting question...

If the platter were magnetic e.g. iron casting then the rotation would induce a current in the coils of the cartridge, though as not well aligned with the field very weak, as well as pull on the cartridge changing vtf, this is well known in the original thorens 124 platter and why they changed to aluminium top platter in 124 mkII
http://www.schopper.ch/index.php?page=non-mac-platter

The magnetic field in cartridge would induce a magnetic field in paramagnetic platter e.g. aluminium/magnesium, and pull it towards each other

although it will effect vtf, though obviously it is static if the platter is of uniform purity, and harmonic if not

If it were made of carbon/copper then the rotation would induce levitating magnetic field(diamagnetic), but this is so weak i think in everyday matters not important