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Cable length?

jeffbrown

jeffbrown

Jun 13, 2007
1,245
1,134
New Hampshire, USA
#1
OK, I understand that for (high end) stereo systems, it is strongly suggested that the cable length from amp to speakers be equal; does that hold true for amp to multiple cabs as well, i.e., can I use a shorter cable from an amp sitting on a stack to the upper-most cab, and a longer one to cab underneath it? Or does it really matter?

TIA
 
#3
jeffbrown said:
OK, I understand that for (high end) stereo systems, it is strongly suggested that the cable length from amp to speakers be equal
Click to expand...
Piffel. Electrons pass through wire at 0.7x speed of light. I'll let you try and figure out the time differential between those passing though 3 feet versus even 300 feet of wire.
BTW, definition of Audiophile: Someone who'll believe anything.
 
#5
I think the only real admonition on stereophobes is to not coil any excess wires and hide them behind the gear. It can create a small air-core transformer and that can degrade sound or cause transients.

I'm not too sure about amplified signals in the power range that we use on our amps-to-cabs, but there may be a corollary too.
 
#8
Gee, thanks, Wes. Very insightful. A newbie/amateur/Mediocre Bassist can rely on you. :eyebrow:

Bill, as usual, your answers are truthful and to-the-point. Your advice is well taken. Many thanks! :) My father is an "audiophile," thus my query. I believe nothing unless I believe in the source.

I thought piffoul was French...
 
#10
billfitzmaurice said:
Piffel. Electrons pass through wire at 0.7x speed of light. I'll let you try and figure out the time differential between those passing though 3 feet versus even 300 feet of wire.
BTW, definition of Audiophile: Someone who'll believe anything.
Click to expand...

Bill, I'm not usually one to question your knowledge, in reading your posts, time and time again, I've seen that you're an expert in your field, but as far as I know, electrons actually travel much slower than that through copper cables. You're saying electrons have a defined speed, whereas I always learned that their speed was dependant on the energy they had.

Edit- I found this little snippet online, "For example, for a copper wire of
radius 1 mm carrying a steady current of 10 amps, the drift velocity is only about 0.024 cm/sec" Now, obviously, increasing the current will increase this velocity, but increasing the radius of the wire will decrease the velocity too. If I'm going wrong, I'd like to be shown how. I'm totally fine with being wrong, but I'm curious enough to want an explanation.

Another edit - I think I've found where the misunderstanding has creeped in. Your figure seems to be the electromagnetic wave propogation, rather than actual electron movement, which is much, much slower.
 
#12
Huh?

marvin-m.png
 
#13
billfitzmaurice said:
If it was 1/10 the speed of light it would still 88,000 times the speed of sound, so the exact figure isn't all that critical.
Click to expand...

My point was more that its not in significant fractions of the speed of light, its usually measured in cm/s, or decimals of that. The speed the actual electrons travel at won't even approach the speed of sound. The electromagnetic wave propogation could very well be up at your 0.7c figure, but the actual speed the electrons travel at won't even be in the same ballpark.

Like I said, I'm open to correction if I'm wrong. I gave a rough figure for the sort of ballpark figures the actual electrons will travel at when I said, "a copper wire of radius 1 mm carrying a steady current of 10 amps, the drift velocity is only about 0.024 cm/sec". Thats a tiny fraction of the speed of sound, let alone the speed of light.
 
#14
dj150888 said:
The speed the actual electrons travel at won't even approach the speed of sound.
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If that was the case no electronic gear would work. Consider the speed that they travel at via the internet, allowing this 'conversation' to take place. Or over telephone lines.
I don't recall who gave me the 0.7C figure, but it was someone who would have known, otherwise I wouldn't have taken his word for it.
 
#16
bongomania said:
Hm, subscribed to observe more clarification of this "speed of electrons" discussion.
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You don't need to be Einstein to figure out that electrons through wire travel at many thousands of times the speed of sound. If they only traveled at the speed of sound it would take your voice an hour to reach someone 778 miles away on the other end of a phone call, and another hour for their reply to be heard by you.
 
#17
billfitzmaurice said:
If that was the case no electronic gear would work. Consider the speed that they travel at via the internet, allowing this 'conversation' to take place. Or over telephone lines.
I don't recall who gave me the 0.7C figure, but it was someone who would have known, otherwise I wouldn't have taken his word for it.
Click to expand...

He's right Bill.

If you could actually mark a specific electron and follow it through a wire you would find it moving exceedingly slowly. Much, much slower than the speed of sound.

Here's an analogy: imagine a tube filled with ping pong balls, say 500 or so, open at each end. Now start pushing new ping pong balls in one end. As each one is pushed in at one end another pops out the other end almost immediately. That's the speed of the electromagnetic wave propagating through the wire.

If you actually follow a specific ball it takes much longer for it to move all the way through the tube and pop out the other end. That's the speed of an electron moving through the wire.
 
#19
projectMalamute said:
He's right Bill.

If you could actually mark a specific electron and follow it through a wire you would find it moving exceedingly slowly. Much, much slower than the speed of sound.

Here's an analogy: imagine a tube filled with ping pong balls, say 500 or so, open at each end. Now start pushing new ping pong balls in one end. As each one is pushed in at one end another pops out the other end almost immediately. That's the speed of the electromagnetic wave propagating through the wire.

If you actually follow a specific ball it takes much longer for it to move all the way through the tube and pop out the other end. That's the speed of an electron moving through the wire.
Click to expand...
If you want to get really precise about it yes, that's true. If I recall correctly from my now totally obsolete undergraduate studies of physics electrons don't flow as water in a pipe, they merely push each other from one atom to another. What matters to us is how long it takes the applied electrical impulse at one end of a wire to arrive at the other end, and that's on average based on a speed of 0.7C.
 

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