A basic questions

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ulot

New Member
Hi i've been told and i get it quiet clearly that the thin cables offer greater resistance to current and signal flow and the longer the cable, the more the resistance but is the effect of this of great importance when it comes to signal transfer? LIke sound and other things?
thanks
And anyone know where i can get basic knowledge about sound? Frequency, dB and stuff.
thanks again.

Dr.EM

New Member
As far as audio goes, you want the lowest resistance cable you can get, without it being too good for the equiptment. I've heard that when setting up a hi-fi system, you should spend 10% budget on cables. I also think its more important with speaker cables as they carry more current.

Don't know too much about sound, but an increment of 3 "actual" dB will be percieved as twice the volume, and a muscal octave is exacly twich the frequency (ie A440Hz up one octave is A880Hz, Hz being the number of oscillations per second)

audioguru

Well-Known Member
No Dr. EM,
A volume change of 3dB is twice or half the power which is hardly noticeable. Your hearing isn't linear, it responds logarithmically so that you can hear a wide range of levels from leaves rustling at a distance to a nearby rocket takeoff.
10db is ten times the power and it sounds twice as loud.

Copper wire is cheap so I would never spend much on it. I don't know why people buy expensive "Monster" cables for speakers when ordinary cheap lampcord wire works the same.

Low capacitance as well as low resistance is important for long microphone-level and line-level signals.

Nigel Goodwin

Super Moderator
Dr.EM said:
As far as audio goes, you want the lowest resistance cable you can get, without it being too good for the equiptment. I've heard that when setting up a hi-fi system, you should spend 10% budget on cables. I also think its more important with speaker cables as they carry more current.

You have no need to spend silly money on cables, it's just a big scam, with the so called 'Monster' cables often performing worse than ones a fraction of the cost.

For speaker cables it's a good idea to use a reasonable thickness, particularly for long runs - but it's nothing to get too excited about. For signal cables the main difference is the amount of screening provided, if you are in a noisey environment you might need to use decent quality screened cables (particularly for microphones).

But most expensive cables are a complete waste of time, never buy anything that says 'monster', 'oxygen free', 'gold plated' etc.

The resistance of copper is very low, and for signal cables it makes very little difference (due to the impedances involved), but for high power speakers a thicker cable will help to reduce any loss - mains cable is as good as anything else for this.

If you want to compare different cables, the only way is to get someone to change cables repeatedly for you, while you do blind listening tests. The person changing the cables writes a list of which ones he used, which he randomly changes about - and you write a list of scores you give the different cables.

I'll be VERY surprised if you can reliably detect a particular cable, or even tell any difference at all!.

David Bridgen

Member
for high power speakers a thicker cable will help to reduce any loss
More importantly it allows the amplifier's low output impedance to properly damp the cone.

mstechca

New Member
ulot said:
Hi i've been told and i get it quiet clearly that the thin cables offer greater resistance to current and signal flow and the longer the cable, the more the resistance but is the effect of this of great importance when it comes to signal transfer? LIke sound and other things?
thanks
And anyone know where i can get basic knowledge about sound? Frequency, dB and stuff.
thanks again.

If you are working on projects that produce a frequency under about 100Mhz, then the only thing that matters the most is the length of the antenna. An antenna can be a piece of wire.

If you are connecting two items together with a cable and both items are individually powered, then make sure that the resistance of the cable is low so that data can pass easier.

Frequency = number of times a second something happens. 100Mhz = 100 million hertz. hertz = times per second. I think Hertz is a name of the person who discovered or invented the term Frequency.

DB = Decibels, a unit which determines the volume of sound. I think a number between 60 and 80 is normal listening level.

Stuff.... What other kind of stuff?

What exactly do you want to do with the cables?

ljcox

Well-Known Member
To cut a long story short.

dB is deciBel. deciBel is one tenth of a Bel presumably named after Alexander Graham Bell. deci is the metric "multiplier" like centi, kilo etc. eg. one decimetre is one tenth of a metre, etc. DeciBel is used since a Bel is too large.

dB is a logarithmic ratio dB = 10 log (P1/P2) where P1 and P2 are the power levels at the input and output of some type of device such as an attenuator, amplifier, telephone line, filter, antenna feeder, etc.

It can also be done with a voltage ratio

dB = 10 log {(V1/V2)^2} = 20 log (V1/V2)

The square is because power is proportional to the square of the voltage

P = {V^2}/ R is the power dissipated in a resistor R if a voltage V is applied to it. Edit. I forgot to include the /, also added {} for clarity.

In the case of sound level, the level of a sound is referred to a particular reference level. ie. it is the ratio between the measured power level and the power of the reference level. It is expressed in dBA. I can't recall what the A means.

Len

stevez

Active Member
You might want to do a little math to see just how much difference the wire does make. I think with audio frequencies we can look at the wire as if it were handling DC - though I'll admit to wondering if the rise time of some sudden increase in volume isn't enough to be affected by inductance. For this discussion I'll stick with DC. Comments by others on this would help me.

My wire tables tell me that 18 ga wire has a resistance of 0.64 ohms per hundred feet. 12 ga wire is 0.16 ohms per hundred feet. I am not sure I'd trust my reference - the table is formatted strangely but the concept is correct - neither wire size has a lot of resistance but it has some and the larger wire is much more conductive (less resistance).

If you were driving 4 ohm speakers that required 50 ft of cable (100 ft total conductor) and we neglect any contact resistance then the series resistance with 18 ga wire is 4.64 ohms and with 12 ga wire it's 4.16 ohms. It would seem that less power could be applied (about 10%) with the 18 ga wire - and that a much greater percentage of that power would be wasted in heating the wire (0.64/4.64) - about 14% vs about 4% with the 12 ga wire - or about 10%. For this simple example that's about a 20% difference.

I generally agree with the statements that you might not ever notice this difference however with a longer cable run it might make a difference. If you were working with 2 ohm speakers the difference might be significant - and with something greater than 4 ohms the difference gets much smaller. As others have said, much of the marketing stuff is just that - marketing stuff. Copper used for even the cheapest wire is still pretty conductive and the differences at best are trivial. Certainly making good connections is an area for improvment - maybe - though the connectors need not be expensive to perform well.

audioguru

Well-Known Member
stevez said:
My wire tables tell me that 18 ga wire has a resistance of 0.64 ohms per hundred feet.
.....then the series resistance with 18 ga wire is 4.64 ohms...

a much greater percentage of that power would be wasted ... - about 14% vs about 4% with the 12 ga wire - or about 10%.

I generally agree with the statements that you might not ever notice this difference.....
That's right, a 10% difference is only about 1dB. :lol:

Oznog

Active Member
The patch cables between devices don't carry significant current, just a voltage signal. Even the cheapest 99 cent ones have a resistance a thousand times to low to ever be detectable with a scope. Nor is gold plating of any difference other than fancy looks. But they do look pretty.

I think it REALLY got out of hand when they went with "toslink", a digital optical cable. It is ridiculous to go optical since the digital signal can be carried flawlessly on any 99 cent copper wire cable and degredation of the signal is impossible. They charge like $20-$100 for those stupid things, just a technoscam.

eblc1388

Active Member
Different cables, length, size, types, etc... certainly make a difference to the final electrical signal. Of course it does because you can see the changes on good instrument.

The main point is whether this changes would make a difference in the music/sound we hear. Audiophiles say/claim they can hear/perceive the differences while most of us can't. There is no right or wrong. I view it the same as religion faith or those myths like walking under a ladder or Friday the thirteen..

In a free country someone can choose to believe the audiophiles while others go with their own instincts.

Come to think of it, if a person get "better satisfaction" listening to music after being sold an expensive interconnecting cable, then the cable is fulfiling its purpose of enhencing listening pleasure of the buyer.

Nigel Goodwin

Super Moderator
eblc1388 said:
Different cables, length, size, types, etc... certainly make a difference to the final electrical signal. Of course it does because you can see the changes on instrument.

Most of the expensive cables don't give any measureable difference (unless you compare then to REALLY crap cables).

Comparing a long thin speaker wire with a short thick one would obviously produce measureable differences, but would probably make very little audible difference (but you should use reasonably thick wires for speakers regardless, and the longer the wire, the thicker it should be).

ulot

New Member
thank you all for the experienced contributions. I was trilled so do mics make much or a diffrence, or how much power your amp. can actually carry?

Nigel Goodwin

Super Moderator
ulot said:
thank you all for the experienced contributions. I was trilled so do mics make much or a diffrence, or how much power your amp. can actually carry?

I'm not very sure what you are asking here?, a mic input on an amplifier should be specifically designed for the type of mic in use - in the past most were high impedance (about 50Kohm), but now low impedance is common (about 600 ohms), and they are often balanced as well. These have drastically different output voltages, low impedance ones need much more gain in the preamplifier - but actual results, with the correct mic and amplifier should be the same.

KMD

New Member
While I agree 100% that the expensive wires are a complete waste of money when it comes to sound quality, the guys I know, that used to compete, swear that it makes a difference to the judges at competitions. Not that any of them could actually hear the difference, but I bet you would get a lower score from some judges if it got around that you used lamp cord for speaker cable .

ljcox

Well-Known Member
eblc1388 said:
There is no right or wrong. I view it the same as religion faith or those myths like walking under a ladder or Friday the thirteen.

I don't walk under ladders if someone is working above, they might drop a hammer on my head.

Len

audioguru

Well-Known Member
KMD said:
the guys I know, that used to compete, swear that it makes a difference to the judges at competitions. Not that any of them could actually hear the difference, but I bet you would get a lower score from some judges if it got around that you used lamp cord for speaker cable.
It sounds like you are talking about car amps with kilowatts of power into a 1 or 2 ohm load. Of course you can't use lamp cord for such high current.

Nigel Goodwin

Super Moderator
KMD said:
While I agree 100% that the expensive wires are a complete waste of money when it comes to sound quality, the guys I know, that used to compete, swear that it makes a difference to the judges at competitions. Not that any of them could actually hear the difference, but I bet you would get a lower score from some judges if it got around that you used lamp cord for speaker cable .

Assuming this means the silly in-car systems, it's all about looks and not performance or quality - and the systems generally have absolutely unbelievably over exaggerated specifications - for a more realistic specification, divide their supposed output powers by at least five or so 8)

But certainly you DON'T want thin speaker wires when you are feeding 1 or 2 ohm loads, you would make too much loss.

audioguru

Well-Known Member
Hi Nigel,
Have you ever been within about 10km from one of those car max sound-pressure competitions? They are absolutely insane! :lol: :lol:
Kilowatts of power (real RMS rated) driving many huge woofers and the cars use Lexan for their glass (guess why). They reach 160dB of sound which is about when air cavitates due to double the air pressure on one wave then total vacuum on the next wave. :lol:

My new computer came with bigger than expected little speakers that are pretty good. They have ports on their backs which allows a loud bass beat to make them jump towards me on each beat. Their movement scares my dog. :lol:

Nigel Goodwin

Super Moderator
audioguru said:
Hi Nigel,
Have you ever been within about 10km from one of those car max sound-pressure competitions? They are absolutely insane! :lol: :lol:
Kilowatts of power (real RMS rated) driving many huge woofers and the cars use Lexan for their glass (guess why). :

No, but I've never seen one rated in RMS watts either - they are usually rated in 'imaginary fictional' power :lol:

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