BigYinUK Posted June 2, 2013 Share Posted June 2, 2013 Hi again Not that I have ever run a system into a 2 ohm load but surely at this low an impedance the resistance of the cable run must come into the equation? Obviously you'd use good quality leads but does it ever cause issues in real life? I.e significant amounts of power being dissipated in the cables? Do you have to use oxygen free copper cables etc to get the best out of a system running at 2 ohm? Regards Link to comment Share on other sites More sharing options...
paulears Posted June 2, 2013 Share Posted June 2, 2013 Indeed it does, but I think most folk on here would just use heavier cable than waste their money on fancy cable with dubious performance claims. I suspect this is one reason why most people would use the shortest speaker cables and put the amps near them, rather than try to squeeze the last drop out of cables. Link to comment Share on other sites More sharing options...
bruce Posted June 2, 2013 Share Posted June 2, 2013 The cable resistance can start to become significant at higher currents - that's one of the reasons why the pros use chunky speaker cables rather than bell wire :) To put it into context, 2.5mm cable has a resistance of around 7 milliohms per metre. So a 10m cable will have a resistance of about an eighth of an ohm, which is probably low enough to be not particularly significant - going to 4mm or 6mm cable drops the figure even further. Move to 0.75mm flex, on the other hand, and the resistance is up over half an ohm, which is very significant on a 2 ohm load. And as for "oxygen free copper" - go and wash your mouth out with snake oil! Link to comment Share on other sites More sharing options...
csg Posted June 2, 2013 Share Posted June 2, 2013 2 ohm operation is rarely ideal, even when cable losses and thermal losses from the amplifiers are acceptable. even when your amplifiers are thermally stable into 2 ohm loads, most will exhibit power supply limitations to a greater or lesser extent and all will have a harder time controlling cone movement due to the lack of a decent damping factor ( the ratio of amplifier output impedance to load impedance) which may produce a softer or less distinct bass. Link to comment Share on other sites More sharing options...
Owain Posted June 2, 2013 Share Posted June 2, 2013 Oxygen freee doesn't necessarily make a difference, conductor size does, but yes, on any low impedance system the cable can be an appreciable part of the load. That's why 100V line was developed for long runs. It's less of an issue nowadays that amplifier power is so cheap, and full-range music speakers tend to be inefficient anyway; even 50% losses in the cables can be tolerated if the overall design allows. Link to comment Share on other sites More sharing options...
Simon Lewis Posted June 2, 2013 Share Posted June 2, 2013 The resistance of the speaker cable will also have an effect upon damping, and the degree to which the amplifier can control (LF) cones. Link to comment Share on other sites More sharing options...
p.k.roberts Posted June 2, 2013 Share Posted June 2, 2013 Just keep your speaker cables like me - thick and short! Link to comment Share on other sites More sharing options...
chelgrian Posted June 3, 2013 Share Posted June 3, 2013 The cable resistance can start to become significant at higher currents - that's one of the reasons why the pros use chunky speaker cables rather than bell wire :) To put it into context, 2.5mm cable has a resistance of around 7 milliohms per metre. So a 10m cable will have a resistance of about an eighth of an ohm, which is probably low enough to be not particularly significant - going to 4mm or 6mm cable drops the figure even further. Move to 0.75mm flex, on the other hand, and the resistance is up over half an ohm, which is very significant on a 2 ohm load. And as for "oxygen free copper" - go and wash your mouth out with snake oil! Do consider weight as well, non-trivial runs of 8x4mm get heavy and expensive. If you caring about cable loss then you also care about losses in passive crossover networks and therefore end up with active crossovers and bi or tri amplified systems and so need more pairs of conductors. People also get it wrong about multi-strand vs solid as well. It's just so the cable is flexible so you can coil it. Even at 20KHz you need a pretty massive cross section before skin effect would make any difference. There was a wonderful story about Quad audio some years ago attending a trade show and being asked all sorts of questions about the shiny orange speaker cable they were using. The audiofools who had been raving about this cable got annoyed when the Quad people said they had forgotten their cables and had dropped off at B&Q on the way to the show and bought an electric lawnmower mains extension cable to use instead. If you want to see the level of madness out there then just browse http://www.russandrews.com/ although you may explode if you read the section on mains cables. Link to comment Share on other sites More sharing options...
gibbothegreat Posted June 3, 2013 Share Posted June 3, 2013 I've always been a cable sceptic too (in the sense of lilac-scented, organically knitted, yoghurt coated...) but it's only fair to share this story from John Taylor at d&b. They'd had someone pestering them at UK HQ in Stroud for a while, wanting to come and show them his super duper hi-spec speaker cable, and asserting what a difference these could make. Needles to say, a variety of palming-off techniques were employed, but he persisted, and in a moment of boredom/weakness someone there agreed to let him come along and show them. It would be fair to say that the approach of the d&b folk present was not totally one of scientific objectivity, which made it rather more surprising when they were indeed able quite clearly to perceive a notable improvement when his cables were used compared to their standard stuff (which isn't exactly bell-wire...). Sad to say I never asked the obvious question, whether they then pursued this at all. Link to comment Share on other sites More sharing options...
RichM Posted June 3, 2013 Share Posted June 3, 2013 It would be fair to say that the approach of the d&b folk present was not totally one of scientific objectivity, which made it rather more surprising when they were indeed able quite clearly to perceive a notable improvement when his cables were used compared to their standard stuff (which isn't exactly bell-wire...). Sad to say I never asked the obvious question, whether they then pursued this at all. I'd be interested to see how the test was done. If it wasn't blind it was useless. Link to comment Share on other sites More sharing options...
gibbothegreat Posted June 3, 2013 Share Posted June 3, 2013 I'd be interested to see how the test was done. If it wasn't blind it was useless.You clearly don't know the folk at d&b, they were about as rigourous in eliminating factors such as confirmation bias as they could be... Link to comment Share on other sites More sharing options...
Jivemaster Posted June 3, 2013 Share Posted June 3, 2013 I dislike using 2 ohm loads as the amps are usually on the edge of their existence. Fatter cable will make a difference a very notable improvement. Consider the cost of copper and the weight of cable especially if several cable must be supported. Link to comment Share on other sites More sharing options...
RichM Posted June 3, 2013 Share Posted June 3, 2013 I'd be interested to see how the test was done. If it wasn't blind it was useless.You clearly don't know the folk at d&b, they were about as rigourous in eliminating factors such as confirmation bias as they could be... I know the guys down there, but to do a proper double blind test is quite a tricky time consuming thing, just wondered how far they'd gone with it. And if these cables really are so god, how come we haven't heard more since? Colour me skeptical :D Link to comment Share on other sites More sharing options...
Owain Posted June 4, 2013 Share Posted June 4, 2013 I dislike using 2 ohm loads as the amps are usually on the edge of their existence. Fatter cable will make a difference a very notable improvement. Consider the cost of copper and the weight of cable especially if several cable must be supported.Surely thinner cable would help as it would add more resistance to the load? Link to comment Share on other sites More sharing options...
timsabre Posted June 4, 2013 Share Posted June 4, 2013 Surely thinner cable would help as it would add more resistance to the load? It would make the amp happier, but would have bad effects on the sound coming out of the loudspeaker, which is after all the object of the exercise. Link to comment Share on other sites More sharing options...
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