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Unequal Speaker Cable Lengths? |
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Groundhog 
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Joined: 31 Oct 2013 Status: Offline Points: 9 |
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 Topic: Unequal Speaker Cable Lengths?Posted: 13 Dec 2013 at 7:13pm |
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I have a question for Graham and any other experts.
Let’s say I want to order Spatia speaker cables for my two-channel system. The speakers are 3m apart; the amp is to the right of the right speaker (it’s not feasible to have the amp between the speakers). I’ll need a 4m length to reach the left speaker. A 1m cable easily reaches the right speaker. Should the right speaker cable be 1m (shortest) or 4m (to match the left)? Why? If this has already been answered, (a) my apologies for not finding it, and (b) could you please point me to that thread? Thanks, -Brent |
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Drewan77
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Joined: 25 May 2013 Location: Chester,England Status: Offline Points: 1544 |
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Posted: 13 Dec 2013 at 8:19pm |
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I am not sure if there is a technical justification to have equal lengths, however I can suggest some practical reasons:
Years ago when I was a poor student, I used speaker cable in unequal lengths but this only worked for the original room. Since then I have used equal lengths because you never know if you will relocate the system or indeed sell the cable. Both are easier with two identical cables |
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Older than I once was, younger than I'll be
............................. Andrew |
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less
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Joined: 27 May 2008 Location: Clevedon Status: Offline Points: 334 |
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Posted: 13 Dec 2013 at 9:29pm |
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Hi, good question.
I agree with the previous post on having equal lengths. The fact is that a signal will propagate along the cable at some percentage of the speed of light. I think, but stand to be corrected, that Graham has suggested in another thread that this is about 60%. I have not done the calculation, it's too late at night  but feel free to do so yourself! You should arrive at difference in propagation over three and one metres of a fraction, a very small fraction, of a second. It should not be audible  The speed of light in a vacuum is given as 299792458 metres per second! Regards Les |
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I don't do mediocrity!
Les Sutherland |
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discrete badger
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Posted: 13 Dec 2013 at 10:43pm |
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Due to room layout and a concrete floor I have 2 metres on the left and nearly 20 metres (!) on the right, 4mm stranded copper. Sounds fine to me.
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Ash
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Joined: 18 Mar 2013 Location: Dorset Status: Offline Points: 4334 |
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Posted: 13 Dec 2013 at 10:44pm |
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You just gave me a flashback with that speed of light stuff. I had to go a look a couple of things up before I was able to find the equation I was thinking of.
c = 1 / sqrt (µ0.ε0) and that, what was it... c= Emax / Bmax ???? I never did manage to understand either of the relationships. |
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We do not see things as they are. We see things as we are.
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Groundhog
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Posted: 14 Dec 2013 at 7:37pm |
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The delay calculation: If the signal propagates at 0.6c, the timing difference is 17 ns (nanoseconds). Under normal listening conditions, sound travels about 6 μm (micrometers) in 17 ns. That’s about the diameter of a human red blood cell. At middle C, the delay is 0.000004 of a wavelength.
So, as Les wrote, the delay should not be audible. Perhaps there are effects other than delay that are audible; I just don’t know what they might be. Andrew, you’ve made a very practical justification for equal cable lengths. In my case, I don’t think it overcomes the inconvenience of having the extra length of cable to manage. I’m still pondering… Thank you all for your input. -Brent |
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discrete badger
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Posted: 14 Dec 2013 at 8:22pm |
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One possible other effect (at least in theory) is that of resistance. For a given unit resistance, longer speaker cables clearly have more resistance than shorter ones.
In theory, for a speaker with frequency-dependent impedance (i.e. all of them to greater or lesser extent), more power will be dissipated in the speaker cable for the frequency ranges which have lower impedance in the speaker. So the frequency response will be altered slightly. When I measured the resistance of my 20m run it was so insignificant compared to the (known) minimum impedance of the speaker I thought it not worth worrying about - and I can certainly hear no differences between left and right. Purists would likely look on in horror!
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