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Question Cable Length Difference

danny-79

Active member
Oct 3, 2020
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The importance of having speaker cables the same length is pretty obvious to why.
Just a random thought. if they were different lengths or a second set of speakers had longer leads, how much extra cable before the delay starts ?
(For the benefit of this say cable is all of same make and brand)
 

Al ears

Moderator
For your home systems cables do not need to be the same lengths, in my opinion. The ones to my AV rear speakers certainly aren't.
You state reasons are obvious but why exactly?
Admittedly, unless you have made your own up, pairs do tend to come in identical lengths because they assume your speakers are equidistant from the amp.
 
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danny-79

Active member
Oct 3, 2020
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If one cable is longer that the other, one speaker will get the signal quicker than the other and cause a delay effect.
Just curious to see how much difference before it’s noticeable
 

12th Monkey

Well-known member
Aug 31, 2015
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A delay starts immediately there is a difference, but an audible one? Let’s say you can hear up to 20kHz (in other words you are young). I think to get out of phase by 180° (which you’d definitely hear as sounds would cancel out) would take half the gap between soundwave peaks - 1/40,000th of a second. (I pick the upper end of the frequency spectrum as the lower the frequency, the greater time would need to elapse to get out of phase and therefore the longer the difference in cable run.)

If the signal travels at (say) 80% of the speed of light, then the question is how long would a cable need to be before it would take 1/40,000 of a second to travel it – which is (299,792,458m/40,000) x 0.8. My maths suggests that’s just under 6km, and I think there would be bigger issues (impedance etc) with trying to run a system with a cable of that length than phase.

As to how far out of phase a signal would need to be before it started messing around with your stereo image I have no idea, but I suspect it would be almost impossible to test as the lengths would be uneconomic and electrically impractical.

I suspect the differences caused by having your speakers at different distances are more noticeable (in theory) as sound travels so much more slowly, but in practice you’d need a ridiculously large space for it to be a practical issue in the domestic space.

I can’t tell you how irritated I’ll be if I’ve c*cked the sums up!
 

Friesiansam

Well-known member
Feb 3, 2015
166
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10,770
If you want the sound from each speaker to be in phase at your ears, your physical distance from each speaker, as you listen, is all you need to worry about. If we assume the maths above is correct, the effect on timing of one speaker cable being 6km longer than the other, is the same as the effect of one speaker being just 85cm further away from you than the other (at standard atmospheric pressure).
 

nopiano

Well-known member
Feb 15, 2009
271
153
19,070
Delay is irrelevant. There are three more real issues:-

1. the longer cable will have fractionally more resistance.
2. you’ll think it sounds unbalanced because you know it is.
3. Its harder to buy, and nigh on impossible to sell unequal lengths.

Problem 2 is mostly why I’d always go with equal lengths. 1 is largely hypothetical. 3 is practical!
 

danny-79

Active member
Oct 3, 2020
20
12
25
Well you learn something new every day. I honestly thought cables needed to all be the same length
i have lots to learn and appreciate the advice. Sill, I’ll keep my cables all the same length. That’s a life time of thinking that way.
 
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Al ears

Moderator
Delay is irrelevant. There are three more real issues:-

1. the longer cable will have fractionally more resistance.
2. you’ll think it sounds unbalanced because you know it is.
3. Its harder to buy, and nigh on impossible to sell unequal lengths.

Problem 2 is mostly why I’d always go with equal lengths. 1 is largely hypothetical. 3 is practical!
Exactly....
 

abacus

Well-known member
Sep 24, 2008
401
156
19,070
Technically, practically & realistically there will be zero difference in even large rooms, however, psychologically it is a different matter.

I know absolutely 100% that it does not make a difference, (Just do a double blind test or use a measurement mike) however if I know that one cable is shorter than the other, then my brain automatically makes the speaker with the shorter cable sound louder, (Even though I know that it is a complete absolute nonsense) so I just make the cables the same length and don’t worry about it.

Bill
 

Longchops

Well-known member
Oct 15, 2020
58
23
45
A delay starts immediately there is a difference, but an audible one? Let’s say you can hear up to 20kHz (in other words you are young). I think to get out of phase by 180° (which you’d definitely hear as sounds would cancel out) would take half the gap between soundwave peaks - 1/40,000th of a second. (I pick the upper end of the frequency spectrum as the lower the frequency, the greater time would need to elapse to get out of phase and therefore the longer the difference in cable run.)

If the signal travels at (say) 80% of the speed of light, then the question is how long would a cable need to be before it would take 1/40,000 of a second to travel it – which is (299,792,458m/40,000) x 0.8. My maths suggests that’s just under 6km, and I think there would be bigger issues (impedance etc) with trying to run a system with a cable of that length than phase.

As to how far out of phase a signal would need to be before it started messing around with your stereo image I have no idea, but I suspect it would be almost impossible to test as the lengths would be uneconomic and electrically impractical.

I suspect the differences caused by having your speakers at different distances are more noticeable (in theory) as sound travels so much more slowly, but in practice you’d need a ridiculously large space for it to be a practical issue in the domestic space.

I can’t tell you how irritated I’ll be if I’ve c*cked the sums up!

Sorry to be anal, this is a very interesting post!

In pro audio we actually have a product for this very issue called 'enhancers' which are basically a high pass filter and a micro delay to basically 'slow down' the higher frequencies because it appears there is a significant spread over even relatively short distances, 6km sounds a bit long tbh.....

You are using the speed of light as a calculation but I'm wondering if it should really be the speed of sound, its a sound wave travelling through a medium isn't it?
 

Longchops

Well-known member
Oct 15, 2020
58
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45
How fast does sound travel through copper? its pretty fast right? Much faster than air. that could be enough to cause a spread surely?
 

shadders

Well-known member
Nov 19, 2009
152
88
18,670
Sorry to be anal, this is a very interesting post!

In pro audio we actually have a product for this very issue called 'enhancers' which are basically a high pass filter and a micro delay to basically 'slow down' the higher frequencies because it appears there is a significant spread over even relatively short distances, 6km sounds a bit long tbh.....

You are using the speed of light as a calculation but I'm wondering if it should really be the speed of sound, its a sound wave travelling through a medium isn't it?
Hi,
I have not checked @12th Monkey calculations, but they are probably right - there is no perceptible delay in the difference speaker lengths.

Is it possible that your pro-audio implementations are using cables that have high capacitance and/or inductance ? which for long runs are a problem.

The speed of a signal down a wire is approximately 0.8 x speed of light as stated above. Signals in wires are electrical, so the speed of light is the correct unit to use.

Regards,
Shadders.
 
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TrevC

Well-known member
Jun 12, 2013
307
131
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Sorry to be anal, this is a very interesting post!

In pro audio we actually have a product for this very issue called 'enhancers' which are basically a high pass filter and a micro delay to basically 'slow down' the higher frequencies because it appears there is a significant spread over even relatively short distances, 6km sounds a bit long tbh.....

You are using the speed of light as a calculation but I'm wondering if it should really be the speed of sound, its a sound wave travelling through a medium isn't it?
The sound travels to your lugholes from the speaker in the form of a pressure wave in the air that travels at the speed of sound, but an electrical signal travels at the speed of light.
 
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Longchops

Well-known member
Oct 15, 2020
58
23
45
Hi,
I have not checked @12th Monkey calculations, but they are probably right - there is no perceptible delay in the difference speaker lengths.

Is it possible that your pro-audio implementations are using cables that have high capacitance and/or inductance ? which for long runs are a problem.

The speed of a signal down a wire is approximately 0.8 x speed of light as stated above. Signals in wires are electrical, so the speed of light is the correct unit to use.

Regards,
Shadders.
Ah....ok I don't understand the physics but I'd take your word for it, but guitar amps are 16 ohms as opposed to the 8 they use in hifi. Would that explain it? Our cables are a lot thicker than yours in general too, maybe that's the reason? Must be much higher resistance. And longer distance too come to think about it, we tend to walk around a lot and need that security.

Enhancers were often referred to as the 'do nothing' effect in guitar but I could definitely hear the difference if I really tried....
 

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