Speaker cable lengths

[Oldpinkman]

Any thoughts about what to do when you don't have a power amp slap bang in the middle of the speakers, and you have a wife who objects to coils of spare cable intruding into the room? I need a 3m length and 1.5m length. I currently have 2 terminated 4m lengths of chord flat cable, both to a greater or lesser extent coiled up out of sight. I have just experimented with some QED 79 strand and cheap banana plugs, and don't notice a difference between equal and unequal lengths ( obviously they are not as open and detailed as the chords). Any experience of whether the same holds true for better cable? And, what's good if I don't decide to cut the chords?

[Reffc]

Any thoughts about what to do when you don't have a power amp slap bang in the middle of the speakers, and you have a wife who objects to coils of spare cable intruding into the room? I need a 3m length and 1.5m length. I currently have 2 terminated 4m lengths of chord flat cable, both to a greater or lesser extent coiled up out of sight. I have just experimented with some QED 79 strand and cheap banana plugs, and don't notice a difference between equal and unequal lengths ( obviously they are not as open and detailed as the chords). Any experience of whether the same holds true for better cable? And, what's good if I don't decide to cut the chords?

Don't worry about it, just use unequal lengths. DC loop resistance is probably less than a few percent of your driver impedance, so the amp won't be bothered whether you use unequal lengths at all. In fact much better to do this than to coil up longer lengths as the act of coiling up cable forms a pretty effective inductor!

[Oldpinkman]

Thanks Paul
I thought as much (the inductance issue is why my preference is for them to sprawl into the living room - Mrs S, otherwise a caring , tolerant and loving wife, doesn't see it that way :doh:). It seems you do just the one speaker cable. Tough call, I know, but if you were me, would you cut the chord or buy some from you? (I may wait for the shelves to get built, and my Quad to come back (banana sockets - the Arcam needs spades, although I could reverse them I suppose (ventricals have combined terminals)
They have bi-wire terminals too. Bi-wire?

[Gordon Steadman]

Any thoughts about what to do when you don't have a power amp slap bang in the middle of the speakers, and you have a wife who objects to coils of spare cable intruding into the room? I need a 3m length and 1.5m length. I currently have 2 terminated 4m lengths of chord flat cable, both to a greater or lesser extent coiled up out of sight. I have just experimented with some QED 79 strand and cheap banana plugs, and don't notice a difference between equal and unequal lengths ( obviously they are not as open and detailed as the chords). Any experience of whether the same holds true for better cable? And, what's good if I don't decide to cut the chords?

Can't you loop the spare cable on the back of the speakers so it doesn't show? Or the 63.s will have a base that could be used?? I don't know if coiling is a good idea though, could it affect the leads in some way??

My previous comments on the choice of wife.........:eyebrows:

[Oldpinkman]

You wait till she comes out to France Gordon.:eek: I promise you she is a significant upgrade on the previous model. I'll chip away at the stacked 57's...

[Reffc]

Thanks Paul
I thought as much (the inductance issue is why my preference is for them to sprawl into the living room - Mrs S, otherwise a caring , tolerant and loving wife, doesn't see it that way :doh:). It seems you do just the one speaker cable. Tough call, I know, but if you were me, would you cut the chord or buy some from you? (I may wait for the shelves to get built, and my Quad to come back (banana sockets - the Arcam needs spades, although I could reverse them I suppose (ventricals have combined terminals)
They have bi-wire terminals too. Bi-wire?

You can loop the spare cable rather than coil it, then just forget any expenditure or upgrades. Either that or cut to length and have it nice and tidy.

Personally, I would single wire rather than bi-wire. The greatest impact of bi-wiring generally tends to be lining the pockets of dealers who sell speaker cable (yes, I know, I know, but I usually advise against it if a customer contacts me!). Bi-wiring can also introduce some crossover distortion which single wiring (and using jumpers) doesn't as it changes the electrical damping that the amp sees (removes it) from the cross connection with the jumper cables. Its such a low increase that its probably not audible, or barely audible, but its probably there nonetheless. It also affects total loop resistance (marginal I know) and can decrease S/N. Single wire every time unless the speaker manufacturer claims that the speakers have specifically been designed for best response bi-wiring (which I doubt). Whilst I am happy to provide some Talk3, I think unless there's something wrong with your current cable, you'd be just as well to cut it to the required length and keep it single wired.

[Clive]

I use speaker cable lengths of 3m and 4.5m and have not noticed any form of imbalance between channels.

[Kember]

Can't you loop the spare cable on the back of the speakers so it doesn't show?

I don't know if coiling is a good idea though, could it affect the leads in some way??


Gordon,

My old chemistry teacher told me to loop cables in figures of eight to avoid induction on speaker and antenna cable. I've done it ever since when my cable is too long and nothing bad has happened. I'd rather do that than chop good cable.

Funnily enough, my wife also objects to having cable all over the floor, but happy to leave her shoes all over the floor for me to trip over. :lol:

Peter

[eardrummer]

I've run unequal lengths of both biwire and single wire for for years without issue. After finding this site and reading the technical article on biwiring, that just confirmed what I already thought - unequal lengths are not worth worrying about!

[walpurgis]

The theory is that inductance from coiling cables can heat them up (it would take a lot of power) or diminish top end output from your speakers, but I've yet to experience any of this. I don't coil mine anyway these days.

I'm fastidious about all my cables being the same length, but on the odd occasion I've used uneven lengths, I've heard no difference.

[Reffc]

The theory is that inductance from coiling cables can heat them up (it would take a lot of power) or diminish top end output from your speakers, but I've yet to experience any of this. I don't coil mine anyway these days.

I'm fastidious about all my cables being the same length, but on the odd occasion I've used uneven lengths, I've heard no difference.


That's right. Depending on the number and size of the coils you can make quite an effective inductor which can affect crossover points/HF and add a fair amount of reactive load to the amp.

[brucew268]

So if someone coiled a speaker cable, how many coils are likely to create an inductor that might have such effect... 2x, 3x, 6x? One 12inch diameter coil would use up about a meter of speaker wire, so it would not take bu 1 or 2 coils to use up a significant excess. I currently have 2coplete coils in a 10inch circle. I don't notice any heat from them but have not tried to check other measurements or sonic effects, so not sure if an issue or not.

Alternatively, I could do a single loop under the bottom shelf of my rack (below the amp having a pretty good power supply). Then I have potential EMI nearfield issues. Any prediction which if any would be more of an issue?

[Oldpinkman]

Thanks for the responses. My pet guru said that uneven lengths would be fine (actually he said "I've told you before - size doesn't matter") but he is a measurements purist. I am reassured to hear nobody from the auditioning camp thinks they can hear an important difference. And for the coilers, I wouldn't get too panicky about inductance either, unless you are winding them round a pencil. However, I think I won't cut my chords. I've had them 20 years, and they may be just the job in France, so I'll get a set made. I don't want to go nutty - I am too tight, and this is hopefully a temporary arrangement in a room set-up with serious compromises. Any suggestions for sensibly priced speaker cable that is a worthwile improvement on QED79. Say £100 for the set?

[Rare Bird]

Funny how people are concious about the length but not the girth? :eyebrows:

[Barry]

Richard - I'm sure by now you will have been reassured that using unequal lengths of speaker cable will not make the slightest difference.



However if you want to be fully reassured, I'll cite a perhaps somewhat extreme example; a situation I have lived with for some thirty years.

Until recently, my power amplifier has been connected to my speakers by two grossly unequal lengths of cable. To be precise, they were 6m and 16m long. Yes, that's right, one length is 2.5x as long as the other!

Did this make any difference? Well on a technical level yes it does, on a practical level, of course not. The cables in question are QED 79-strand with PVC insulation.

The cable length difference is 10m, suggesting a signal delay difference of no more than 67ns (more likely it is ~50ns). Is this important? No. The typical group delay of your amplifier will be say 150 - 200ns. This is of course irrelevent, but let us assume the tolerance on this figure is 10 - 20%, the variation between channels will be say 30 - 40ns; similar to the variation in propagation delay time of the cables. To put this into perspective, 50ns corresponds to a change of acoustic path length (the distance between your speakers and your ears) of < 20um! Does anyone sit that precisely?

Secondly, the resistance of the two cables measures as 0.104 and 0.202 Ohm respectively. Given an amplifier output impedance of 0.03 Ohm, and a mean speaker impedance of 10 Ohm, this corresponds to a channel difference of 0.084 dB. Most amplifiers have a channel balance of not much better than 0.1dB, and the unit-to-unit variation in sensitivity between the two speakers will also be greater than this. Anyway this correction (if it could be heard!) can be adjusted with the balance control.

Finally, the differing speaker cable lengths will have a bearing on the effective damping factor of the amplifier as seen by the speaker. Given the above figures, this translates as an effective damping factor of 43.1 and 74.6 respectively. This might seem to be significant, but it's not - especially if you use electrostatic speakers (which I do), as there is very little 'mass' to dampen.

So don't worry at all about unqual speaker cable lengths.



As an aside, if you do have equal cable lengths but need to 'bunch up' the excess cable, the usual advice is to fold the cable in a serpentine (boustrophidon) fashion, rather than coiling up the cable. This is because coiling a cable can increase its inductance. However one shouldn't get too carried away with his. Speaker cables are twin conductor cables. The magnetic field set up by one conductor is equal and opposite to that set up by the return conductor (the same current flows in both). Since the two conductors are in close proximlty, the magnetic fields will virtually cancel one another. True, what vestigial magnetic fields there are (between the two conductors) will cause the overall inductance to be increased, but only if the cable is very tightly wound or coiled up.

[twickers]

Richard - I'm sure by now you will have been reassured that using unequal lengths of speaker cable will not make the slightest difference.



However if you want to be fully reassured, I'll cite a perhaps somewhat extreme example; a situation I have lived with for some thirty years.

Until recently, my power amplifier has been connected to my speakers by two grossly unequal lengths of cable. To be precise, they were 6m and 16m long. Yes, that's right, one length is 2.5x as long as the other!

Did this make any difference? Well on a technical level yes it does, on a practical level, of course not. The cables in question are QED 79-strand with PVC insulation.

The cable length difference is 10m, suggesting a signal delay difference of no more than 67ns (more likely it is ~50ns). Is this important? No. The typical group delay of your amplifier will be say 150 - 200ns. This is of course irrelevent, but let us assume the tolerance on this figure is 10 - 20%, the variation between channels will be say 30 - 40ns; similar to the variation in propagation delay time of the cables. To put this into perspective, 50ns corresponds to a change of acoustic path length (the distance between your speakers and your ears) of < 20um! Does anyone sit that precisely?

Secondly, the resistance of the two cables measures as 0.104 and 0.202 Ohm respectively. Given an amplifier output impedance of 0.03 Ohm, and a mean speaker impedance of 10 Ohm, this corresponds to a channel difference of 0.084 dB. Most amplifiers have a channel balance of not much better than 0.1dB, and the unit-to-unit variation in sensitivity between the two speakers will also be greater than this. Anyway this correction (if it could be heard!) can be adjusted with the balance control.

Finally, the differing speaker cable lengths will have a bearing on the effective damping factor of the amplifier as seen by the speaker. Given the above figures, this translates as an effective damping factor of 43.1 and 74.6 respectively. This might seem to be significant, but it's not - especially if you use electrostatic speakers (which I do), as there is very little 'mass' to dampen.

So don't worry at all about unqual speaker cable lengths.



As an aside, if you do have equal cable lengths but need to 'bunch up' the excess cable, the usual advice is to fold the cable in a serpentine (boustrophidon) fashion, rather than coiling up the cable. This is because coiling a cable can increase its inductance. However one shouldn't get too carried away with his. Speaker cables are twin conductor cables. The magnetic field set up by one conductor is equal and opposite to that set up by the return conductor (the same current flows in both). Since the two conductors are in close proximlty, the magnetic fields will virtually cancel one another. True, what vestigial magnetic fields there are (between the two conductors) will cause the overall inductance to be increased, but only if the cable is very tightly wound or coiled up.

:youtheman: