dvidos Posted April 14, 2008 Share Posted April 14, 2008 Hello, a long long (really long) time ago, I had read in a book that the speaker cables should be kept of equal length. It was the era when Hi-Fi was emerging. But that was a long time ago... I am now in a situation where, in an open air theatre, I am supposed to prepare the cables from the amp to the speakers. One speaker needs about 20 to 25 meters of cable. The other, closer to the amp, needs only 10 meters. And budget is limited enough to make me ask you: Is it acceptable, in the world of pro audio, for the speaker cables to be of different length? Most of the time the setup will be dual mono. Will there be a time difference between the two speakers? Do I need to have both cables at 25m? Or I can get away with a longer and a shorter cable? My guess is that the time difference will be so small that I should not care, but I wanted to verify before cutting the cable. Thank you,Dimitris. Link to comment Share on other sites More sharing options...
patrick_keys Posted April 14, 2008 Share Posted April 14, 2008 I am now in a situation where, in an open air theatre, I am supposed to prepare the cables from the amp to the speakers. One speaker needs about 20 to 25 meters of cable. The other, closer to the amp, needs only 10 meters. And budget is limited enough to make me ask you: Is it acceptable, in the world of pro audio, for the speaker cables to be of different length? Most of the time the setup will be dual mono. Will there be a time difference between the two speakers? Do I need to have both cables at 25m? Or I can get away with a longer and a shorter cable? Personally, I wouldn't worry about it - if there is any scientific evidence to suggest that they should be the same length, any degradation in sound quality is likely to be masked by 'outdoor' sounds such as police sirens, helicopters, dogs, drunk people and wildlife if it still exists... Link to comment Share on other sites More sharing options...
Rich Posted April 14, 2008 Share Posted April 14, 2008 According to my D&B speadsheet, presuming your cable is 2.5mm, and you're load is 8 ohms, then the drop in level for the extra 15m will be -0.23dB, nothing to worry about. As for delay, I assume from my distant A level physics that we can take the speed of the signal down the cable to be the speed of an electron, which is around 3X10 to the power of 8 m/s, so you shouldn't be able to notice any delay. Link to comment Share on other sites More sharing options...
dvidos Posted April 14, 2008 Author Share Posted April 14, 2008 Thank you Gentlemen!This is what I wanted to hear. Indeed Rich, it is 2.5mm cable driving 8 ohms.Now, where are those cutters... :) Link to comment Share on other sites More sharing options...
Shez Posted April 14, 2008 Share Posted April 14, 2008 we can take the speed of the signal down the cable to be the speed of an electron, which is around 3X10 to the power of 8 m/s [pedant] Electrons actually move more slowly than me. The current travels nearly at the speed of light, so as you say, no problems there. The slow speed of sound emanating from the speakers is far more of an issue than the current in the cables. :) [/pedant] The only time I can think of when cable length starts to matter is when dealing with video - an RGB signal won't line up properly if the individual coaxes are significantly different lengths. Link to comment Share on other sites More sharing options...
Rob_Beech Posted April 15, 2008 Share Posted April 15, 2008 As the other have said, it really makes very little (no noticeable difference) for this sort of application. And the only difference you would start to see as you went to the extremes is a drop in level. Nothing a quick tweak of the DSP can't solve. 5m of 2.5mm against 100metres at 2ohms, a significantly larger difference, but still nothing to concern yourself over. If it really bothers you. Split your amp racks in 2 and buy another processor / crossover identical and run a rack for SL and a rack for SR. Link to comment Share on other sites More sharing options...
dbuckley Posted April 15, 2008 Share Posted April 15, 2008 The only time I can think of when cable length starts to matter is when dealing with video - an RGB signal won't line up properly if the individual coaxes are significantly different lengths. Heck, if you use Cat6 for RGB then you get colour smearing due to the pair lengths being different due to the widely varying twist pitch... Link to comment Share on other sites More sharing options...
Bobbsy Posted April 15, 2008 Share Posted April 15, 2008 We're drifting off topic here, but just to say that, in a broadcast environment, we rarely tried to run RGB for runs over a few meters for that very reason. The industry flirted with analogue component routing in the days of Betacam/M2 VTRs but I was lucky in that installations I worked on jumped from composite distribution to serial digital without the intermediate step. Even so, I remember the days of "timed cable lengths" so everything was synchronous at the routing switcher. Our central racks area was on 300mm high computer flooring so we could hide the extra cable associated with nearby VTRs so they'd be timed to match studios which were 80 or 90 metres away! We now return to our scheduled discussion of speaker cable lengths! Bob Link to comment Share on other sites More sharing options...
Rich Posted April 15, 2008 Share Posted April 15, 2008 we can take the speed of the signal down the cable to be the speed of an electron, which is around 3X10 to the power of 8 m/s [pedant] Electrons actually move more slowly than me. The current travels nearly at the speed of light, so as you say, no problems there. The slow speed of sound emanating from the speakers is far more of an issue than the current in the cables. [/pedant] Oh really, thanks for that Shez. Link to comment Share on other sites More sharing options...
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