Ferrous metal or magnets near cables- problem, or no problem?

[highfigh]

It's well known that the audio/video world is filled with people who thing that one cable or another could prevent disasters, solve world problems and complete the lives of their users, but I have a serious question about what happens when a cable is installed (laid, or fastened) on ferrous metal or near a magnet. Knowing that current in a conductor creates a magnetic field (weaker or stronger, based on the current) and this can couple with other cables, I haven't seen anything other than cable stands that are supposed to address this.

The reason I'm posting this thread is due to the fact that I'm doing an AV installation and the only place to run speaker cabling is near/under radiators for the heat and the covers are made of sheet steel. I'd rather not see the cabling, so I thought about the cable management devices that use magnets to allow a wire tie or strip of Velcro to secure the cables, but I thought "If the system is paying at a high level, How do these rare earth magnets affect the signal?" and if they actually have an effect, "Will it affect an amplifier?".

As good of an idea as it seems and knowing that people will sell anything to make a buck, and these aren't cheap (the magnets are, but my distributor charges over $2 each for some of them and I think that's insane. I can get magnets from Rockler Woodworking for less than that but it's not made for cable management.

If I had a scope, I would test this- if anyone has an oscilloscope and has the time to look at the waveform of low/mid/high frequencies when a speaker cable is (very) near a rare earth magnet, it would be a great service. If it's not too much trouble, maybe it could be tested with line audio, too.

Thanks, in advance.

 

[Bucknekked]

It's well known that the audio/video world is filled with people who thing that one cable or another could prevent disasters, solve world problems and complete the lives of their users, but I have a serious question about what happens when a cable is installed (laid, or fastened) on ferrous metal or near a magnet. Knowing that current in a conductor creates a magnetic field (weaker or stronger, based on the current) and this can couple with other cables, I haven't seen anything other than cable stands that are supposed to address this.

The reason I'm posting this thread is due to the fact that I'm doing an AV installation and the only place to run speaker cabling is near/under radiators for the heat and the covers are made of sheet steel. I'd rather not see the cabling, so I thought about the cable management devices that use magnets to allow a wire tie or strip of Velcro to secure the cables, but I thought "If the system is paying at a high level, How do these rare earth magnets affect the signal?" and if they actually have an effect, "Will it affect an amplifier?".

As good of an idea as it seems and knowing that people will sell anything to make a buck, and these aren't cheap (the magnets are, but my distributor charges over $2 each for some of them and I think that's insane. I can get magnets from Rockler Woodworking for less than that but it's not made for cable management.

If I had a scope, I would test this- if anyone has an oscilloscope and has the time to look at the waveform of low/mid/high frequencies when a speaker cable is (very) near a rare earth magnet, it would be a great service. If it's not too much trouble, maybe it could be tested with line audio, too.

Thanks, in advance.

What an interesting problem. I am interested in the answer. You already know more about the problem than I do because you've thought enough to ask. I'll be interested n watching this thread.

 

[TLS Guy]

It's well known that the audio/video world is filled with people who thing that one cable or another could prevent disasters, solve world problems and complete the lives of their users, but I have a serious question about what happens when a cable is installed (laid, or fastened) on ferrous metal or near a magnet. Knowing that current in a conductor creates a magnetic field (weaker or stronger, based on the current) and this can couple with other cables, I haven't seen anything other than cable stands that are supposed to address this.

The reason I'm posting this thread is due to the fact that I'm doing an AV installation and the only place to run speaker cabling is near/under radiators for the heat and the covers are made of sheet steel. I'd rather not see the cabling, so I thought about the cable management devices that use magnets to allow a wire tie or strip of Velcro to secure the cables, but I thought "If the system is paying at a high level, How do these rare earth magnets affect the signal?" and if they actually have an effect, "Will it affect an amplifier?".

As good of an idea as it seems and knowing that people will sell anything to make a buck, and these aren't cheap (the magnets are, but my distributor charges over $2 each for some of them and I think that's insane. I can get magnets from Rockler Woodworking for less than that but it's not made for cable management.

If I had a scope, I would test this- if anyone has an oscilloscope and has the time to look at the waveform of low/mid/high frequencies when a speaker cable is (very) near a rare earth magnet, it would be a great service. If it's not too much trouble, maybe it could be tested with line audio, too.

Thanks, in advance.

A wire carrying an electric current generates an electric field. This will react with a field from a magnet, maximal when the fields are perpendicular. So there will be a force on the flowing electrons. This is the Lorentz force. Therefore it follows there will be a voltage across the field. This is the Hall effect. It looks like a resistance, but isn't as that is an inherent property of the conductor. However it looks the same as a voltage across an inserted resistor.

Now a speaker wire has two conductors with current at any instant flowing in opposite directions. So the magnetic fields of the two conductors are 180 degrees out of phase and will cancel each other out. So there will be no Hall effect as long as the conductors are perfectly parallel. So do not use twisted cable.

The Hall effect is widely used in automobile sensors, such as wheel sensors in ABS braking systems and crankshaft position sensors. In fact in modern automobiles there are about two Hall effect sensors on everything that turns!

 

[highfigh]

A wire carrying an electric current generates an electric field. This will react with a field from a magnet, maximal when the fields are perpendicular. So there will be a force on the flowing electrons. This is the Lorentz force. Therefore it follows there will be a voltage across the field. This is the Hall effect. It looks like a resistance, but isn't as that is an inherent property of the conductor. However it looks the same as a voltage across an inserted resistor.

Now a speaker wire has two conductors with current at any instant flowing in opposite directions. So the magnetic fields of the two conductors are 180 degrees out of phase and will cancel each other out. So there will be no Hall effect as long as the conductors are perfectly parallel. So do not use twisted cable.

The Hall effect is widely used in automobile sensors, such as wheel sensors in ABS braking systems and crankshaft position sensors. In fact in modern automobiles there are about two Hall effect sensors on everything that turns!

Familiar with Hall Effect- used in some tape recorder motors, too.

Knowing that current is induced when a magnet moves relative to a coil, the coil moves relative to a magnet or the current in a conductor alternates near another coil or conductor that's parallel and in close proximity, would a small magnet that is placed at some point in the cable's length act as a resistor, to some extent (dictated by the strength of the magnetic field)? The magnets are small round or square discs, laying flat on the metal. I have some that are made for attaching a removable panel, so they have a hole in the center that would create more of a doughnut-shaped field, rather than each face having a different polarity.

Don't use twisted wire, because? Twisted pair reduces common mode noise (not that it's a major problem with speaker cable)- are you saying twisted wire shouldn't be used if magnetic cable clips are used or don't use twisted speaker cable, for anything?

This makes me wonder if this type of cable management should be used for communication cabling at all, unless the cable is in conduit made from ferrous metal.

 

[TLS Guy]

Familiar with Hall Effect- used in some tape recorder motors, too.

Knowing that current is induced when a magnet moves relative to a coil, the coil moves relative to a magnet or the current in a conductor alternates near another coil or conductor that's parallel and in close proximity, would a small magnet that is placed at some point in the cable's length act as a resistor, to some extent (dictated by the strength of the magnetic field)? The magnets are small round or square discs, laying flat on the metal. I have some that are made for attaching a removable panel, so they have a hole in the center that would create more of a doughnut-shaped field, rather than each face having a different polarity.

Don't use twisted wire, because? Twisted pair reduces common mode noise (not that it's a major problem with speaker cable)- are you saying twisted wire shouldn't be used if magnetic cable clips are used or don't use twisted speaker cable, for anything?

This makes me wonder if this type of cable management should be used for communication cabling at all, unless the cable is in conduit made from ferrous metal.

I'm just saying that if you use magnets to not use twisted cable. If both conductors experience the same magnetic filed you will be fine, because the electromagnetic field in the two conducting cores will cancel each other, and there will be no issue with the magnets.

 

[slipperybidness]

A wire carrying an electric current generates an electric field. This will react with a field from a magnet, maximal when the fields are perpendicular. So there will be a force on the flowing electrons. This is the Lorentz force. Therefore it follows there will be a voltage across the field. This is the Hall effect. It looks like a resistance, but isn't as that is an inherent property of the conductor. However it looks the same as a voltage across an inserted resistor.

Now a speaker wire has two conductors with current at any instant flowing in opposite directions. So the magnetic fields of the two conductors are 180 degrees out of phase and will cancel each other out. So there will be no Hall effect as long as the conductors are perfectly parallel. So do not use twisted cable.

The Hall effect is widely used in automobile sensors, such as wheel sensors in ABS braking systems and crankshaft position sensors. In fact in modern automobiles there are about two Hall effect sensors on everything that turns!

Just a side note--the triggers for the XBOX One controllers are also Hall Effect sensors. This is a change form the old XBOX 360 controllers where they used potentiometers.

 

[Kip_Dynamite]

A wire carrying an electric current generates an electric field. This will react with a field from a magnet, maximal when the fields are perpendicular. So there will be a force on the flowing electrons. This is the Lorentz force. Therefore it follows there will be a voltage across the field. This is the Hall effect. It looks like a resistance, but isn't as that is an inherent property of the conductor. However it looks the same as a voltage across an inserted resistor.

Now a speaker wire has two conductors with current at any instant flowing in opposite directions. So the magnetic fields of the two conductors are 180 degrees out of phase and will cancel each other out. So there will be no Hall effect as long as the conductors are perfectly parallel. So do not use twisted cable.

The Hall effect is widely used in automobile sensors, such as wheel sensors in ABS braking systems and crankshaft position sensors. In fact in modern automobiles there are about two Hall effect sensors on everything that turns!

Twisted wire pairs are often used to shield from outside interference. I am not aware of any actual electrical theory that establishes this is somehow bad on an audio wire.

 

[Speedskater]

Yes, twisted pairs is the correct way to go.

You often see this in the writings of the interference experts:
Jim Brown, Henry Ott (RIP) and Bill Whitlock.
* * * * * * * * * * * *
Now days, pro-audio often uses un-shielded CAT cable for XLR balanced interconnects.
CAT cable consists of 4 twisted pairs.

 

[highfigh]

This wasn't about noise or line level audio, it was about having a series of magnetic fields at fairly regular intervals along speaker cable and any affects they may produce.

As it turned out, and I'm not going to remove the magnets and test it, there was no apparent affect- the sound is fine and the magnets worked great for securing the cables out of sight.

I think Bill has retired- it would be great if they could produce some kind of interactive VR so people could experience his lectures and Q&A- those were great.