Follow-up to the recent discussion of cabling...

I'm planning to install speaker cables in-wall (in-basement actually). They'd run right next to AC power lines. I was thinking to put them in conduit to protect from interference, but then I thought, maybe the interference won't be strong enough for the speakers to notice. The speakers are currently CSW Ensemble, about 6 Ohm, but I may add smaller surround ones.

I know electrical code insists on separation. The wire in question is not twisted, so the interference may happen.

I was also thinking of protecting phone lines from the speaker cables, but these will be cat 5 so it's probably safe to run them together.

What's your take?

It wouldn't matter if they were twisted or not. Twisted pairs like in a CAT5 cable only reject interference because in the case of a network device the receiving end uses a difference amp to get the desired signal off the wires, that way the interfence (which is likely the same on both wires because of the twisting) cancels itself out when you combine the two signals from each wire in the pair. Using twisted pair wiring in instances where there is no difference amp involved won't give you any protection at all from interference, because the twisting of the wires only strives to ensure that the interference that is present in that location will be the same on both wires. In fact, (unshielded, like CAT5) twisted pair wiring in and of itself rejects absolutely no interference, everything leaks into your signal path, you get 100% of the interference onto your cable. It requires the extra electronics in the connected devices to take that interference and make it work against itself by cancelling itself out in the difference amp. It inverts the signal from one of the pair and mixes them together, and that causes the interfence to disappear.

The levels that the speaker works at is relatively high and I'd be very surprised if you ever noticed any interference as you might with line-level cables. The voltage involved is just so much higher than line-level signals that even if you had the worst possible interference it isn't going to amount to much.

<edit> clarification

I can't answer the question, but I'd just wanted to correct this : the voltage in line and speakers connectors is about the same when you listen at moderated volumes (hundreds of milivolts).

EDIT : the ampli acts then as a current amplifier, not a voltage amplifier. Since it can also amplify the voltage (listening louder), and P=UI, it's called a "power" amplifier.
Anyway, your point remains valid in theory, the interference not being rejected because of increased voltage, but because of decreased output impedance (=increased current).

You must have some insanely sensitive speakers. Most speakers I see are in the high 80's to mid 90's on a 2.83v reference signal. Most line level signals are well below 1v, which is in the exponential range as far as difference from speaker-level goes.

If the electrical & speaker wires are in close proximity to each other over long lengths, then you might get a 50/60 Hz hum.

xen-uno

Yes, but for about 90 dB. I can't listen at 90 dB in my flat without having the neighbours knock on the door. I listen around 70 db, thus 20 dB below, thus 0.283 Volts instead of 2.83

hmm, yeah, just checked my center channel currently playing some music about the same loudness and myself speaking at a moderate volume, and it is reading between 500 and 600 millivolts. I don't have any line-level devices at the moment so I can't see what they might be outputting, but it's probably around the same. In all my life I have never heard any interference which crept in on the speaker wires though, and I've had wires in all sorts of places, including running parallel with power wires. That's not to say there isn't any interference there. But I sincerely doubt there's ever going to be any amount that could be heard through the speaker, going by my own personal experience.

It is always a good idea to seperate power (mains voltage) and signal cables in seperate conduits. The reason for this is to make sure that even if the insulation on some of the cables is compromised then line voltage doesn't get applied to the signal cables. If this were to happen it would be a severe fire and safety risk. This sort of thing happens more often than you can imagine - all sorts of things tend to make holes in those nice plastic coverings on cables and wires.

On day you might playing around at the back of your amp one day when you suddenly find your right hand grounded and your left at 220v. This is potentially fatal, especially if you have sweaty hands or a heart condition. While this is unlikely if your house has properly installed modern earth leakage protection - it is still a risk and is a good enough reason to put your speaker cables in conduits or ducts. It's probably also the law in your area.

Electrical codes such as this exist for a very good reason. If you feel like flouting the law, then do something that doesn't endanger others - like operating heavy machinery when drunk

You could use ethernet duct (with the click on cover) or standard PVC conduit. Conduit is much cheaper and working with it is very easy. It will be a couple hour's work to install it properly - or you could ask a local electrician to hire out one of their labourers for a morning.

I don't see interference being a big problem if you seperate the cables by a couple of centimeters. You might want to condsider seperating them from the phone cables too - otherwise you will hear wierd clicks when the phone rings or is hung up.

The UK regulations do not require the use of conduit (ducts), but they do specify a minimum separation between mains cables and any other cables. IIRC the minimum separation is 50mm (about 2 inches), but please no one use this advice without checking because it's just from memory.

I found a useful thread about balanced line-level audio and power cables here, but it's not relevant!

I've never had trouble with speaker wires running parallel with (and adjacent to) mains cable, but I did once have a big problem where the line level signal and the speaker signal were both sent (unscreened!) up/down the same 6 core cable. Above a certain volume, the amplifier would start smoking because of the feedback between the two signals within the cable. Very bad!

I've never had mains hum on insanely long runs (10m+) of very cheap line-level cable, but I have experienced some RF interference on insanely long runs (50m) of very cheap SPDIF.


In conclusion, for speaker cable, parallel to mains cable is probably OK, but leave several inches gap for safety reasons. And check local regulations!

Cheers,
David.

This is impossible. Even if you've taken the wallplate off, removed the wires from the wall receptacle, and have the bare wires sitting in front of you waiting to be grabbed. You cannot grab the ground with one hand and get zapped by 220/240 with the other hand. Why? Because there is no 220/240 voltage source.

Either I am being very stupid here or we are misunderstanding each other. If you open up a plugpoint's wall panel and grab hold of the live with one hand and your other hand is grounded, a current corresponding to ~220VRMS (~311V peak to peak) divided by your body's resistance will flow through your chest, possibly causing difficulties with your heart.

According to my multimeter, the resistance from my right palm to my left is about 900KOhm. This depends a lot on whether your hands are damp. I have a lovely scar between the forefinger and thumb of my right hand which will bear witness to the fact that current will flow through your body. In the USA the voltage will be less, ~110VRMS (~156V peak to peak) but a similar thing will happen.

I am sorry if I am misunderstanding what you are trying to get at. Please rephrase it for my benefit.

Speaking as a qualified approved electrician ( now non practising ) I agree.I'm not sure what the current United Kingdom I.E.E wiring regulations specify but they are more safety conscious that many other country's.

High voltage conductors that are used in domestic installations have a amount of Resistance/ insulation needed for protecting that wire.mainly two types of protection are used for insulation - electrical and mechanical.

Electrical 7 mechnical protection ( rubber insulation ) used mainly to stop the conductors current from breaking out of the confines of the wires conductor and zapping ya in the ass! .

And mechanical protection ( metal conduits - tubes - etc etc )
Modern fuse's can use both electrical and mechanical protection to break an electrical circuit.

So by placing speaker cable next to Mains voltage cable what do you compromise?

well if any breakdown of the main cables insulation should occur lets say as a worst example in a typical UK domestic installation, you could have a speaker cable that is subject to anywhere between 5 amps to 100 Amps ( Modern showers can take this amount ) the usual cables you have for T.V's,amps,radios will have a max load usually ( due to the fuse protection ) of 5 amps or 13 amps to the plug ( for electrical protection for the electrical equipment), and 15 amps or 30 amps from the main fuse board to protect the wires/cables supplying that socket( UK only ).

Current measured in ampheres is always seeking the easiest path similar to water in a stream,if your speaker wire lay-ed next to the main cable is the path of least resistance then your nice new speakers could have a quick blast of 240 V 100 Amps.
This maybe for only Milli seconds provided the fuse breaks,though this may not cause much of a risk to your health( unless your touching metal on the audio system and have a weak heart), I'm guessing the speakers electronic components will kinda be fused and frizzle like a fly in a flame .

Just use common sense! thats mostly what electrical installation is about,don't Mix and match electrical components with hugely different voltages and currents together ,unless these components are designed and shielded specifically for that kind of installation.

I believe most speaker cable is not designed to run or be next to mains voltage cable,and even if it was it's better practice if possible to keep these things separate if @ all possible.

As for will this effect the sound you pick up with your speakers?

Dunno never tried it .

But if you begin to hear you kettle being boiled and your microwave ping! from your speakers...?that should'nt be happenning ! Just kidding.

It's the safety of your main electrical installation that matters far more than any artifacts your speakers may pick up.

Please forgive me, I let it slip my mind that not everyone lives in North America. Here we do have 220/240V supplies for clothes driers and ovens etc, but they are derived from two opposite polarity 110/120V supplies. So I was trying to point out that you could only receive a 110/120V shock in the manner described.

Off topic :

A speaker plugged into 230 Volts will fly through the room (the moving part), and what's left might catch fire.

The domestic current is 50 or 60 Hz, and that's what is most dangerous for the body, rather than the intensity of the current. It sends electric shoks in the body 100 or 120 times per second. This is slow enough to stress the muscles, and fast enough to prevent them to relax between two shocks. Thus it paralizes the parts of the body into which the current flows. You can't take away the hand that grabbed the wire, and the heart can stop beating.

_Shorty : the same exists in Europe and can supply 380 Volts, but it's very rare. In my grandparents house (1972) , the electric heaters are plugged into 380 Volts terminals. This has been supressed from domestic instalations now.

Lets keep this realistic though,the only way a speaker connection is going too have a potential difference of 240 Volts connected across its load for any amount of time other than Milli seconds is if for testing reasons you directly wired this your self and took out any form of protection device ( fuse ) .

And even then I imagine the tiny carrying current capacity of the speakers components / wiring, would act much like a fuse and melt in Milli seconds.

' The domestic current is 50 or 60 Hz' erm...! no it's not,current is measured in amps,Hz which stands for cycles per second is a measurement of the oscillation or frequency of the voltage.Thats why you'll often see 240 Volts 60 Hz in the UK,Where 240 Volts is the voltage and 60 Hz the frequency of that voltage supplied by the power company.So when you read on the back or ALL Domestic electrical equipment bought in the UK ' 240v 50/60 Hz ' this is the Voltage and frequency of the voltage that the device is been manufactured for.So in ALL of the UK the domestic electrical suppliers have by law to provide a constant voltage of 240V +/- 5 % ( I think 5 % is the allowed difference @ present, maybe 6%) and @ a frequency range at or between 50 to 60 Hz per second.

The measurement of frequency Hz can exceed far more than 50-60 Hz without their being any risk @ all.A everyday audio Cd's you put into your CD player have been recorded and plays back using a sampling quality of 44100Hz,I produce music on my computer sometimes using has high as 96 KHz.What this actually does is, the increased cycles per second (frequency) enables the recorded Audio to take more tiny snap shots of sound per second thus producing or recording a better quality sound.Yet since human hearing can't hear in the high range of even 44100Hz such techniques are often discussed as being practical or not.
Why aren't these very highly frequency's a possible electrical hazzard..?because the current is tiny.

I = V/R This is part of Ohms theory , current ( I) is equal to the potential difference ( Volts V) divided by the resistance.

To simplifier this imagine a stream of water .The water being the current,the voltage being the potential or force applied to that water, which in a streams case would be caused by gravity and the amount of water trying to get from a higher to a lower point. like the current trying to get from a high point of resistance too a lower point.

V = I * R -- voltage is equal to current multiplied resistance .

Voltage is the potential difference and is in direct relation to current ( amps ) you can't have one with out the other in a COMPLETED electrical circuit with a load across it.Resistance which occurs in all electrical conductors is in indirect relation to current,the higher the resistance the lower the current unless more voltage (force) is applied.
resistance is not electricity,it is the force opposed to the electricity from heading toward a place of lessor resistance.

P = V * I -- Power is equal to voltage multiplied by current

Power is the energy .
when voltage is applied across a load ( Amplifier ) a current is carried and energy is being consumed and turned into other forms of energy - sound - heat - vibration(sound) - etc etc.

I think what I have said is quite accurate though a electrical engineer may be able to smooth the finer details and rough edge's of my explanation and understanding of electricity.

So too sum up and get back on topic just make sure your speaker cable is a little stream completely shielded from other streams and especially from big rivers like main cable .

High Impedance connections as signal ones, that connect low impedance preamp out to high impedance man amp, or cd to preamp, are more sensitive to noise.

Low impedance conn like speaker ones, wit 8-2 ohm impedance load are much less sensitive.
Besides low level signals are amplified many times and noise too.
So don't worry about speaker cables near power line, but if your speaker have integrated amplification (as pc ones) then u can't do it.
Bye

It is a matter of Amplifiers.To me the good amplifiers does not interfere with AC source.Most probably the noise can only be caused by AC interferrence in preamp part.I.e where your audio is pre-amplified and fed to poweramp.This region is more sensitive to noise and interferrence.

Thus if you are not using sheilded cables to input through amps,you will get noise.For speakers,if the amp is in-built,then there is probability of noise,which can be reduced by proper earthig and using shielded cables.

-Tuning

OT....

Bongo yep,

UK mains is officially 230V +/-10%, 50Hz. We do not have a 60Hz supply here.

http://www.diyfaq.org.uk/electrical.html#240V

Historically, we had many different voltages and frequencies (at least 110V-240V, at least 30-50Hz and DC, in different areas) but that's well before my lifetime. Very old equipment which operates on a variety of voltages (via a switch on the back) is designed to be compatible with all the different electrical supplies then existing across the UK. New equipment operating at a variety of supply voltages or frequencies is designed to work in different parts of the world. Many laptop transformers, DVD players etc can be connected to any power supply in the world (with the right plug). That's the only reason you see 50/60Hz and 100-240V equipment in the UK.


Whatever - keep the mains wiring separated from the speaker wiring by a few inches, so there's absolutely no chance of anyone ever driving a nail through both, and making the speakers live.

Cheers,
David.

OT - still -

A 50Hz AC voltage is more likely to cause heart complications than a DC voltage of the same amplitude when applied between your hands. This is because of the muscle spasming that Bongo described earlier. However, this pattern does not continue as the frequency increases. Modern electrical cauterising guns (used in hospitals all the time) use several thousand volts AC at a frequency of several kilohertz. The effect of this is that the current does not interfere with the electrical processes in the body, but there is still enough current to burn the flesh at the point where it is applied.

In order to get a shock from a power source it needs two things - sufficient voltage to induce a large current (200mA starts getting dangerous) and be able to source sufficient current (again, about 200mA). Electric fences, for example, typically operate at about 9000V but aren't dangerous (to healthy humans) because they are designed to not source more than a few milliamps. Similarly a home arc welding machine can source about 100 Amps, but the voltage (12-60V typically) isn't enough to cause a current to flow across your body's resistance.

Mains electricity is dangerous because it has both - a plug point has enough voltage to cause a current to flow and even an ordinary domestic socket can source 15Amps. An earth leakage protection system (I think called a ground fault protector on the left of the Atlantic) is designed to cut off the current once about 50mA is flowing to ground. It won't protect you if you attach yourself between Live and Neutral, but it will protect you if you attach yourself between earth and live (or neutral).

I took an old driver with a torn diaphragm and attached it to the mains. After a couple of seconds it burnt off one of the little spade connectors, but not before drawing a peak of about 10 amps and getting hot enough to burn a ring onto my workbench desk. At risk of sounding like a TV special - don't try it at home.

Yup! I've heard them called R.C.D's - residual current device's.They have by law to be fitted on any outside installation in the UK and Alithough many new mains boards do have them built in, theirs still many house's, my own rented one included, that don't have these very sensitive earth leakage protection device's.

To quote 2Bdecided 'UK mains is officially 230V +/-10%, 50Hz. We do not have a 60Hz supply here'

yes your right about the only 50Hz,I'd forget about it being more 230V and joined the 99% of the british public in believing it was 240V not that it matters at all to the british public to be 10 volts off .

Just think then..?the electricitys suppliers are robbing the majority of the british electrical consumers of approx 10 Volts.

AFAIR, the frequency regulation in the UK is maintained at an incredibly high level. Over a set period the number of cycles delivered has to remain at a defined constant figure of 50Hz, any period of under frequency has to be balanced by a corresponding period of over frequency. This is necessary for equipment that uses a timer derived from the mains. e.g. wall clocks.

I do agree with Bongo Yep that electrical safty should far outweigh any worries about interference.

UJ

I don't know how long is the period, but in France, the frequency doesn't seem very accurate. Using a quartz locked Technics SL-1200 turntable, one can see locking the engine to the crystal clock that the stroboscope, that displays the speed according to the 50 or 60 Hz frequency, is way out of tune.

Had a quick look and could find only one oblique reference that seemed to suggest it was done on a daily basis, but no longer bothered with.
Probably not much that uses it as a timing signal nowadays anyway, most wall clocks run on batteries.

UJ

Well, clocks use power supply frequency as a consequence of its precision and not the opposite

50Hz period is exact cause many power plants must be connected to a single network between different countries too, and if one of them has a 0.0001% period difference with others, it dissipates a lot of energy working "against" others.

So not only it must be 50Hz, but it must be 50Hz in phase with others

Thank you everybody. Especially to cabbagerat for trying to start a fire on my behalf. ;-)

The advice about safety is well taken.

Now, back to interference.



Hm... can you fill me in with the theory I'm missing here? I mean, you get an identical interference waveform applied to both connectors of a speaker. The waveform applied to both ends of the coil induces no current thereby canceling itself. Doesn't it happen in plain old telephones exactly like that?



That means conduit for speaker wire AND for phone. Are you sure I will hear the clicks? I was thinking that the occasional phone transient should not impress a 6 Ohm speaker, while the interference from the speaker wire should be canceled in cat 5 phone wiring. In fact, shouldn't the interference from a twisted pair cancel itself?

Hmm, yeah, perhaps you're correct in the case of a speaker since it simply moves in relation to the difference in voltage on the two wires.

The twisted pair in telephones is only one part of a two part system. There is also electronics on either end of that twisted pair that are taking measures to ensure the desired signal is retained and undesired signals are discarded. It isn't only the twisting of the wire that does this. Telephones are balanced devices, that is, the voice/audio signal is present on *both* wires and is in opposite polarity on each wire. Those two signals are then taken by a difference amp, which outputs a single signal which comprises only the differences between the two original signals. Interference will be the same on both those signal wires, and thus will be eliminated by the subtraction process in the difference amp. Since the intended signal is intentionally opposite, it remains intact after being subtracted from one another. Consider this:

signal = +6
put through balanced system 'transmitter' which duplicates and inverts the signal on wire2.
signal1/wire1 = +6
signal2/wire2 = -6
transmit across wire pair and then received by balanced system 'receiver' which subtracts signal2/wire2 from signal1/wire1.
((+6) - (-6)) / 2 = +6

interference = +5
signal1/wire1 = +5
signal2/wire2 = +5
(+5) - (+5) = 0

I thought that as soon as this topic was posted. But on further thought, though the same interference would hit both + and - cables, they can be connected differently within the amplifier. Thus, each cable sees a slightly different impedance, and the same interference will induce a different current. So, there's a theoretical reason why you might hear something at the speaker.

As I've already said: in practice, forget it.

Cheers,
David.

hmm, good point, hadn't thought that far about it

Yes, your analysis is correct, up to a point. Two wires next to each other will see the same voltage in the same phase caused by "voltage" pickup from a power line through distributed capacitance, whether they're twisted or not. What happens as a result of the connection impedances in the loop, whether nonlinear or not, will affect the current flow. Twisting the wire doesn't help in reducing this interference.

A pair is actually twisted for a different reason. The source of interference being addressed is voltage developed from magnetic flux passing through an area surrounded by a closed, conducting wire; like the coil in a motor. This is the main source of interference pickup from AC voltages ( it doesn't exist with DC voltage sources). Twisting a pair keeps the area through which a magnetic field can pass, small and the induced voltages are cancelled between twists.

I was looking at this interference issue because I'm rewiring my family room (USA) with wires for a 5.1 speaker system, and one of the wiring manuals from a supplier of media systems suggested keeping speaker wire in the walls 3 to 4 ft away from power lines. This seemed very excessive to me, and almost impossible, so I started looking for information. I joined this group to respond to some comments on this issue.

The comments by those of you who have never seen a disturbing interference have helped me a great deal. I intend to pretty much ignore any risk from power line interference like 60 cycle hum. I will not install a speaker line for any distance next to a power line, but I intend to cross over one or more, and go through common holes in a 2X4.

I also plan to use simple 16 AWG (not twisted) 2 conductor speaker wire. The contentious arguments over wire, coatings and connectors on this and other forums have resulted in completely unsupported conclusions. I'm surprised at the small amount of science in arguments of many of the commercial companies. The only parameter that matters, within the bandwidth of the audio spectrum, is the total resistance between the amplifier and the speaker. Period. In fact, with modern feedback audio electronics the importance of that parameter is debatable.

well, no sense wasting power. Or having slightly mismatched levels from short runs to front speakers and long runs to rear speakers. Might as well use some 16AWG or 14AWG wire and not worry or waste. (Even if it would only amount to 1 ohm difference with 24AWG @ 30 feet, still wasting...)

I agree.

For solid wire the resistance of 24 AWG wire is about 26 ohms/1000' and for 16 AWG wire about 4 ohms/1000'. At 30 ft, the 24 AWG wire has 0.8 ohms of resistance and 16 AWG has about 0.13 ohms. Approximately 20% of your power (with an 8 ohm speaker resistance) will go into heating the wire (2 wires - drive and return). Wasteful. Under the same circumstances only about 3% is wasted in heating with 16 AWG wire. What I've been able to find in the literature is that no listening difference can be detected if the wire resistance is kept below about 5% of a speaker resistance. So, I'm staying with 16 AWG. All of my runs are less than 50 ft, and less than 100 watts per channel.

I'm curious; can hear the difference between near and far speakers using the same gauge wire and no volume adjustability between near and far?

And, back on topic; has anyone actually heard 60 cycle hum with modern electronics and speaker wires too close to in-house power wires? I'm thinking that it may also depend on what is being powered. Running an air conditioner or a large motor with high inductance may be more likely to cause problems than just turning on lights.