Electromagnetic Interference in Speaker Cables? (video)

[Cbdb2]

Thats wrong. They add up but are scaled depending on the output impedance of the voltage sources. Try to put a signal generator on the output of the amp. Connect your preamp out to your power amp out,(different signals) do you think your signal will be a simple addition, or will the power amp swamp the pre. The power amp is a voltage source that will keep that voltage constant no matter what the load is doing, even if its injecting current into the amp. And the wire source will have a very high impedance, ie how much current will it put out.

 

[Lambda]

Thats wrong. Try to put a signal generator on the output of the amp. Better yet why don't you connect 2 power amps outputs with different signals together, you think the signals will add up! Lol.

They are not in parallel, they are in series.

 

[Cbdb2]

That's wrong.
Your amp is generally a voltage source. so it makes sure its output = input * gain.
If you now induce a voltage or curren in the wire your speaker sees this voltage or current + what ever the amp is outputting.

Repeating your error doesnt make it right. If your amp makes sure the output=Input*gain then it has to deal with the error signal to do this. It sees the error thru the feedback and corrects for it. Why don't you try simming the effect. How do you sim the induced voltge? With a votge source with a much larger impedance.

 

[Cbdb2]

They are not in parallel, they are in series.

..

??? Do the math.

 

[Lambda]

All the current that is inductively coupled has to flow trough the speaker since there is no other current part.

 

[solderdude]

2 wires close together in one cable carrying current in opposite directions next to another cable with 2 wires running a current in opposite direction do not work like an air-core transformer. Maybe a little if over a very long length the cable is not twisted.

Just try it. put 2 cables next to each other over a few meters length. Then run power through one cable and connect a speaker to the other cable which you have to short at the other end.

HF in common mode sure.

 

[dualazmak]

Well,,, my dear ASR friends,

I have little interest on the (endless?) theoretical arguments, and also little interest on power cable's possible electromagnetic interference on speaker cables...

The title of the thread is "Electromagnetic Interference in Speaker Cables?", and I understand it as "Do electromagnetic interferences affect speaker level signals?", and my clear answer is "Yes they do!".

In my previous post #129 and #132, I shared the well audible electromagnetic interferences on "speaker cable signals", and I know/understand how to minimize or avoid such mal-interferences; that's all....

Am I wrong here?

 

[solderdude]

I did my burn-in just for sure before daily use

What's there to burn-in ?
Noticed you had multiple inductors and so they were not all under ideal circumstances so one can expect some air-transformer effects.
Have made some wireless power transmission using a inductors with a substantial air gap. Yes efficiency is poor but some power gets through.

 

[solderdude]

The title of the thread is "Electromagnetic Interference in Speaker Cables?", and I understand it as "Do electromagnetic interferences affect speaker level signal?", and my clear answer is "Yes they do!".

Sure they do for RF in common mode. Depending on the amplifier design and coupled power some RF may enter the amp and get 'AM detected'.

 

[Lambda]

Maybe a little if over a very long length the cable is not twisted.

And that why they came up with twisted pairs.

??? Do the math.

Look again you have drawn something in Parallel...
Why? there is nothing there in parallel?

The cable induction is in series.

2 wires close together in one cable carrying current in opposite directions next to another cable with 2 wires running a current in opposite direction do not work like an air-core transformer

The bigger the loop area the the more inductance the is be in general.
its a long but very narrow coil with one turen so ist magnetic feeld can't reach verry far.
cables must be close together and not twisted for inductive coupling.
So cheap and small cables with the conductors close together are actually maybe better...

 

[dualazmak]

....
Have made some wireless power transmission using a inductors with a substantial air gap. Yes efficiency is poor but some power gets through.

And almost all of the commercially available speakers have "such" LC-network with multiple coils (inductors) close together.... We know how to minimize or avoid such coil-to-coil (indoctor-to-inductor) audible interferences. In acctual circumstances, such very faint interference cannot be heard (or even cannot be measured) since all the SP drivers sing together...

Sure they do for RF in common mode. Depending on the amplifier design and coupled power some RF may enter the amp and get 'AM detected'.

Yes, and we know how to minimize or avoid such mal-electromagnetic interferences...

I assume these are the possible conclusions of this thread,,, if my understanding of "Do electromagnetic interferences affect speaker level signals?" is OK. Do we need further more discussions?

Sorry for my rather naive inquiry.

 

[solderdude]

And almost all of the commercially available speakers have "such" LC-network with multiple coils (inductors) close together.... We know how to minimize or avoid such coil-to-coil (indoctor-to-inductor) audible interferences.

Yes, mostly just 2 or 3 under 90 degree angles. In worst case (speaker is mono) there is a slight coupling and would thus only 'bleed' a very low level and most likely phase shifted 'signal' into the woofer or tweeter at very small levels and frequencies those drivers are not very efficient at.
I noticed more than 3 inductors and some under non 90 degree angles which induces a bit more.
There can be substantial currents running through those inductors though.
A way to avoid induction using more than 3 inductors could be to spread over 2 PCB's which are separated at a distance in the speaker.

 

[solderdude]

And that why they came up with twisted pairs.

Yes, that'l work quite well certainly for higher frequencies. For speaker cables running alongside mains cables this isn't really needed though as the 'efficiency' for audio frequency coupling is low, the impedances involved are low (for audio frequencies/mains+harmonics) and because the current flows in 2 directions in a cable (with conductors usually very close) the magnetic field that would do the induction is very low to begin with.
A non-issue really. The 'air core transformer' picture which is used as an example is totally inappropriate as evidence for how this would work.

 

[DonH56]

Amplifier feedback is usually sensed at the output of the amplifier. Anything that tries to move the output unrelated to the signal and within the feedback (loop) bandwidth will be suppressed by feedback. If you apply a modulating voltage on the amplifier's output, whether 60 Hz coupled noise, back-EMF from the speaker, or RFI, the amplifier will reject it as best it is able. The problem for audio amplifiers isn't usually power-line noise injected into the speaker cables (usually inductively if at all) but RFI that is well outside the feedback loop's bandwidth.

 

[Lambda]

The 'air core transformer' picture which is used as an example is totally inappropriate as evidence for how this would work.

It still works like this. the effect of it is minimal and its an non-issue.
But the principle is still the same.

 

[solderdude]

Amplifier feedback is usually sensed at the output of the amplifier. Anything that tries to move the output unrelated to the signal and within the feedback (loop) bandwidth will be suppressed by feedback. If you apply a modulating voltage on the amplifier's output, whether 60 Hz coupled noise, back-EMF from the speaker, or RFI, the amplifier will reject it as best it is able. The problem for audio amplifiers isn't usually power-line noise injected into the speaker cables (usually inductively if at all) but RFI that is well outside the feedback loop's bandwidth.

That, and the issue with RF is that it can find its way 'in' via other paths than the feedback loop when high enough in frequency and power and internal trace/wire routing is not very HF friendly.

 

[Cbdb2]

Amplifier feedback is usually sensed at the output of the amplifier. Anything that tries to move the output unrelated to the signal and within the feedback (loop) bandwidth will be suppressed by feedback. If you apply a modulating voltage on the amplifier's output, whether 60 Hz coupled noise, back-EMF from the speaker, or RFI, the amplifier will reject it as best it is able. The problem for audio amplifiers isn't usually power-line noise injected into the speaker cables (usually inductively if at all) but RFI that is well outside the feedback loop's bandwidth.

Trying to explain that for 2 pages.

 

[dualazmak]

........
A way to avoid induction using more than 3 inductors could be to spread over 2 PCB's which are separated at a distance in the speaker.

Yes, this is why I wrote at the end of my post #132 that "I understand and agree that several high-end HiFi speaker manufacturers are designing their LC-network with rather far distance between coil(s) for woofers and coil(s) for high range drivers."

Also the coils/inductors in LC-network, together with capacitors, cause extra power load to the amplifier (and also phase rotation).

These are two of the several major reasons rationalize multichannel multi-amplifier system (like my project) eliminating all the LC-network caps and coils (inductors) and directly dedicatedly driving the SP drivers by individual amplifier, as well as carefully eliminating magnetic susceptible metals in speaker level signal handlings.

Again, in any way, my point here in this thread is: "Electromagnetic interferences more or less do deteriorate speaker level signals, and we know many ways/measures to minimize and/or eliminate such interferences."

(And I believe usual AC power cables sitting near to the SP cables do not interfere the SP signals in audioble magnitude.)

 

[fmplayer]

I don’t think you mean ‘exacerbated’. Regardless, there is no reliable evidence suggesting that blind people actually do have compensatory ‘super senses’. Although Ernest Bramah’s fictional blind detective could read newsprint using his fingertips...

Oups. False friend. In french (I'm french, sorry ;-) ) it does not mean it is for worse. I meant something more like emphasized. And yes, people who have a deficiency of one of the senses compensate one way or the other. Typically blind people rely on hearing to be aware of their environment (ok, maybe not like bats), but you get the point. Think of Daredevil...
Whatever, they are not influenced by other factors than hearing, provided you don't told them what they are listening to.

 

[fmplayer]

Yes, this is why I wrote at the end of my post #132 that "I understand and agree that several high-end HiFi speaker manufacturers are designing their LC-network with rather far distance between coil(s) for woofers and coil(s) for high range drivers."

Also the coils/inductors in LC-network, together with capacitors, cause extra power load to the amplifier (and also phase rotation).

The reason for this is the variation of the effective inductance value, which introduces variation in Xover frequency as illustrated by Troels Gravesen (see 'Placement of coils in crossover networks' http://www.troelsgravesen.dk/coils.htm). This variation can't be simply calculated and ruins the hard work put into making a crossover.
Of course, active filtering eliminates the problem