Electromagnetic Interference in Speaker Cables? (video)

[roskodan]

A simple calculation of the worst case scenario will prove that the induced noise power to signal power ratio in a speaker cable (when used as speaker cable, not as interconnect) is beyond any theoretical possibility it could be audible. (Amirm actually makes that point in his previous video)

Why?

Because noise induced in speaker cables does not get amplified.

You can wrap your speaker cable around your amplifier and you wont hear a thing because of that. The transformer inside is a pretty big EM noise generator.

But, put your mobile phone near a cheap powered speaker and it's gonna buzz like your morning alarm when a call triggers switching noise from your mobile phone. Because the amplifier circuitry inside is not shielded and the noise generated is in the audible spectrum.

 

[amirm]

Danny's video is a mess and Amir's uses a powered up IEC mains cable with zero current flowing through it, alongside a loopback speaker cable to the AP. That proves nothing. Hang an amplifier, or high current device off the mains IEC cable and place them alongside each other and please show us the results.

Happy to. I connected the Emotiva BasX A-100 to the second channel in Audio Precision and adjusted the volume to get 70+ watts in one channel. That is total of 140 watts. With class AB inefficiencies, it is pulling even more power than that. I then used twist ties to parallel about a 6 inch section to the speaker wire. Here are the results:

Overall levels of mains leakage has only gone up a couple of dBs which could be a function of using BasX power cord (which is dual conductor like a speaker wire). The new components are the harmonics but they are no more significant than the primary mains frequency at some -128 dB.

This brings us to your starting comment. Of course there is current flowing in my original mains cable even though it is not terminated. That cable has capacitance between its two conductors. That creates an AC impedance that while high at mains frequencies, is being driven by very high voltage of mains. So naturally it creates a loop and current does flow. Same reason you can get electrocuted if you touch the end of a mains cable even though you are not a piece of wire. You have impedance so current flows.

As an aside, see how much the amplifier is pumping into the speaker in mains frequencies directly! Peak at 60 Hz is whopping 65 dB "louder" than mains induced through inductive effect of mains cable.

 

[Balle Clorin]

Power cable need to be terminated plugged to something running, as Restorer-John said.

 

[Labjr]

Power cable need to be terminated plugged to something running, as Restorer-John said.

Wouldn't the two cables have to be looped around each other for there to be some sort of inductive interference?

 

[Wes]

Wouldn't the two cables have to be looped around each other for there to be some sort of inductive interference?

It's a quantitative issue. Induction happens between my phone charger and the Mars lander.

 

[pjug]

As already pointed out, the fields from the two power cord wires should cancel. So why don't you make a power cord with separated wires and see if a single wire induces more interference? Because that would be a typical scenario. Joking of course; I really think this kind of thing can swamp your time if you aren't careful.

 

[Lambda]

Of course there is current flowing in my original mains cable even though it is not terminated. That cable has capacitance between its two conductors. That creates an AC impedance that while high at mains frequencies, is being driven by very high voltage of mains. So naturally it creates a loop and current does flow.

The cable has what... like 200pF? that's maybe >0.01mAat 60Hz
Over the total cable... and the magnetic field cancels out because current flows in opposing directions....

So 140W over 6 inch section is sufficient to introduce 3 peaks over -130dB (in how many ohms load)?
So what would a >2kW space heater do if the cables runs parallel for 2m?
Or worse a load with phase cut dimming...

Not realistic? I would say more realistic then the 10µA test with the 15MOhm cable impedance as load.
And differently realistic in the PA and Theater world.

Wouldn't the two cables have to be looped around each other for there to be some sort of inductive interference?

No.

. So why don't you make a power cord with separated wires and see if a single wire induces more interference? Because that would be a typical scenario

Have you seen the garden horses sized audiophile cables.... basically doing this...

A simple calculation of the worst case scenario will prove that the induced noise power to signal power ratio in a speaker cable (when used as speaker cable, not as interconnect) is beyond any theoretical possibility it could be audible.

Please provide us with this simple calculation!
Because i'm to stupid to find it simple and i would have to refer to my physics formula paintings.

 

[amirm]

So what would a >2kW space heater do if the cables runs parallel for 2m?

And that scenario covers how many audiophile setups? Go ahead and set that up and see if you can hear the effect. If you can't, then that is that.

 

[Mnyb]

Speaker wires do act as inductors but in a normal domestic environment only tiny currents are induced in them, which won't impact sound quality of a stereo system.

There are some circumstances, however, where stronger currents could be induced. I would not, for example, drape my speaker wires over the 150 kva power distribution transformer that supplies my city block with power. Doing so might induce a bit of audible 60 Hz hum.

Also probably would be wise to site your speaker wires a reasonable distance away from the Large Hadron Collider, as there are some wicked AC magnetic fields there. Military rail guns should also be avoided if possible. Large electric motors, like those driving diesel-electric locomotives, could also cause trouble, so move any of those out of your living room.

Stay away from magnetars, too. They're big trouble.

Frankly I'm surprised anyone with even basic knowledge of physics would think that putting a large coil next to a speaker wire proves anything, except, don't put a large electromagnetic coil next to your speaker wires.

Yeas i work with lage AC and DC motors in industrial applications VSD drive systems (Frequency converters and DC drives ) , i reckon home environment basically EMF and RFI and magnetic field clean in comparison . in the 90 when we still had CRT monitors for our tool PC we could not have it to close to these things the picture would get all wavy and modulated by the some 1000 amps of currents nearby .

Some converters for electrolysis processes and aluminium smelting and arc furnaces are kind of scary when the field is such that you feel the torque in your hand tools such as screw drivers etc when they want to align in the field and not stay where you put them ( not my main field of work but been there ) leave your credit card in the car don't have a pacemaker

 

[roskodan]

Please provide us with this simple calculation!
Because i'm to stupid to find it simple and i would have to refer to my physics formula paintings.

I believe you meant "Because i'm too stupid to".

 

[amirm]

The cable has what... like 200pF? that's maybe >0.01mAat 60Hz

It is progress after you said this:

So there was no current going trug the mains cable?

You worried about capacitive coupling between mains cable and speaker cable but are dismissive of the same between two conductors of the mains cable which are far closer to each other?

 

[DonH56]

Noise on speaker cables can be amplified -- it depends upon the feedback circuit and output stage topology. But, at power-line frequencies of 50~120 Hz or so, feedback is working just fine and the effective output impedance is so small as to preclude any but pathological cases rarely seen in the home. In the pro world, it happens more often than we'd like, typically smaller venues that run a single small trench through which power, mic, line, and speaker cables get bundled together from back to front of the house (venue, building). The coupling mechanism is primarily inductive, not capacitive, as pointed out above.

At RF, the output impedance is usually high, and you hope the amp designer has included proper RFI suppression at the output and/or feedback circuit to prevent RFI demodulation and amplification back to the speakers.

IME/IMO - Don

 

[Klint]

I would realy like to se a equipment review now.
Don’t see this ending any time soon.

 

[amirm]

I would realy like to se a equipment review now.

That's my plan for the next video.

 

[Klint]

That's my plan for the next video.

Thanks Amir

 

[GimeDsp]

I love the video's about audio reviews! Now lets get some audio about video reviews?

 

[Lambda]

And that scenario covers how many audiophile setups?

As i said more then the <10µA test you made a video about.

I mean there is not only the power lines going to the HiFi setup in my house has more tings that consume current and emit magnetic fields
and people seem to use this:

You worried about capacitive coupling between mains cable and speaker cable but are dismissive of the same between two conductors of the mains cable which are far closer to each other?

The current of a view micro amp will produce a weak magnetic field (mostly at the beginning of the cable and almost non at the end)
most of this will cancel out.
So the effect of an magnetic field from a view micro amps is for me negligible! (since "normal devices" can uses 10s of amps)
A view microamps into the speaker cable is not the same thing! (as a view microamps into a power cabel next to a speaker cable)

You can chose to acknowledge that the initial test had significant flaws since your current was like one millionth of a typical current
Or you can chose to nitpick because technically there was current even if its only one millionth (of an transformer inrush current or something)

But then its funny to say my assumption of a view kW load is untypical while insisting your µW test from the video was valid and conclusive.

Choseing to insist the test was valid with µAs sound like a Danny thing to me.

I believe you meant "Because i'm too stupid to".

Your right, only proofing my point...
I'm waiting for this simple calculations showing the inductive coupling

 

[GGroch]

Amir, perhaps be ready to change plans? In the next episode Danny may provide the blind A/B test proof we have all been waiting for.

At the end of his video Danny says he will: "Move to the listening room, where we will talk about what is really necessary to hear differences in cable. What will help you hear those differences, and what will keep you from hearing those differences."

This should be interesting. Will he:

1. Execute a statistically significant blind A/B test proving that counter-rotated braided cables provide real audible benefits over zip cord, and in doing so become famous and make us all eat crow. OR

2. Explain why Blind A/B listening tests are invalid; a fatally flawed concept supported only by flat earthers trying to prove their own biases.**

3. Will he make any mention at all of the cognitive bias inherent in any sighted listening tests?

While another direct response to Danny may not be justified, at some point I would like to see Amir address the cognitive bias that fuels the audiofool industry. Perhaps this would be a good topic to tackle with Audioholics, or as an interview with an expert like J.J. here at ASR. The topic has been tackled elsewhere, but the Amir has proven to be an effective communicator on complex topics and I am sure he would open some minds.

**Aside, What are the arguments some audiophiles make as to why blind testing is invalid? I am sure there are threads here that address it and I want to read up.

 

[respice finem]

Cable discussions are always longer than cables themselves - they don't have an end at all.
But admittedly, they're entertaining.

 

[roskodan]

Your right, only proofing my point...
I'm waiting for this simple calculations showing the inductive coupling

I'm waiting for folks to start winding their speaker cables around their amps.