Speaker Cable length and sound

To many ads? Support ODJT and see no ads!
MADNESS

MADNESS

Well-Known DJ
Dec 20, 2006
2,293
49
65
Florence, AZ
www.primetimedj.net
OK I know this is sound set up 101, but want to get a refresher course from the pros here at ODJT.

1. When setting up speakers, should all cable lengths be the same?

2. If yes, at what length do can the human ear start hearing the change in sound?

3. What do you do to correct this problem, so all sound is equal?

Here is the scenario, I work a venue in Florence AZ and they want to begin having me set up in another area of the facility. Which is not a problem for me, however I usually plug into the venue sound system, which is about 75 feet away, give or take.
The venue would like me to continue using their sound system, however I am concerned that having my speakers plugged in with 25 foot cables and then a cable running 25 feet into their system and the to their speakers, could cause a sound problem.
 
MADNESS said:
1. When setting up speakers, should all cable lengths be the same?
Click to expand...

Yes. Ideally, all the cables going to cabinets that are producing the same content should have the same lengths. But perhaps not for the reasons that you think.


The speed of light (the rate at which signal travels through cable) is much, much, MUCH greater than the speed of sound. So there is very little difference in the relative phase of sound from a cabinet that has 10ft of cable between the source and the cabinet, and a cabinet that has 100ft od cable length between the source and the cabinet.

What does make a difference is the impedance that the wire length adds to the total load on the amp channel. In general, the rule of thumb is that cable should add no more than 5% to the total impedance on the amp channel. For 10-20ft distance, this means that 14ga wire is acceptable. For up to 50ft runs, 12ga wire is required. And it is never recommended to send amplified signal more than 50ft.

MADNESS said:
2. If yes, at what length do can the human ear start hearing the change in sound?
Click to expand...

That depends on the specific change you are asking about, the frequency of the sound, and the SPL of the sound.

Delay below 100Hz does not become audible until there is ~20ms of total delay. But, in the 300Hz to 5kHz "speech band" delay as low at 1ms is perceptible.

Changes in SPL are generally noticeable between 1dB and 2dB, depending on the remaining content.

MADNESS said:
Here is the scenario, I work a venue in Florence AZ and they want to begin having me set up in another area of the facility. Which is not a problem for me, however I usually plug into the venue sound system, which is about 75 feet away, give or take.
The venue would like me to continue using their sound system, however I am concerned that having my speakers plugged in with 25 foot cables and then a cable running 25 feet into their system and the to their speakers, could cause a sound problem.
Click to expand...

The issues you are facing have very little to do with the overall length of the cables, but more to do with the impedance load that is added, and the relative SPL and phase of the system.

Unless you can separately EQ your system and the house system...with an RTA for guidance...I would just proceed and not worry about the issues.
 
Don't worry about 50 even 100 feet you nor anyone else is going to notice it!
 
Its my practice to run the shortest run of cable from amps to my cabinets that is posible. Nothing to do with delay but why waste power in super long runs of speaker cables. If you run a setup with bass bins your amp will controll the woofers (damping factor) with shorter, fatter ( wire guage) cables. I try to use 12 guage for both tops and bottoms and my runs are usually 30'.
 
The damping factor is the biggest issue as far as I am concerned as well, but generally that applies to the larger drivers 15" and 18" running sub frequencies,
 
MADNESS said:
OK I know this is sound set up 101, but want to get a refresher course from the pros here at ODJT.

1. When setting up speakers, should all cable lengths be the same?

2. If yes, at what length do can the human ear start hearing the change in sound?

3. What do you do to correct this problem, so all sound is equal?

Here is the scenario, I work a venue in Florence AZ and they want to begin having me set up in another area of the facility. Which is not a problem for me, however I usually plug into the venue sound system, which is about 75 feet away, give or take.
The venue would like me to continue using their sound system, however I am concerned that having my speakers plugged in with 25 foot cables and then a cable running 25 feet into their system and the to their speakers, could cause a sound problem.
Click to expand...

1. Hardcore audiophiles will say 'yes' - but in all honesty, most of them believe the FUD that's pumped out like the sewage at the treatment plant. No. The cables lengths don't have to be 'equal'. I wouldn't use a 5' cables and a 500' cable, because that sort of set up just needs to be review for stupidity. But the cables length has little to no impact on the sound.

2. As I said above, I wouldn't worry about it.

3. Change the cable length or use a delay.

Given your setup, I wouldn't worry about it. The cable lengths are going to have a FAR less impact than the speaker placement.
 
Well... you guys have left me little to say.... LOL... but I'll highlight a few points.... in any environment with some background noise, it's highly unlikely that you'll ever notice a difference of 50 to 100' in the cable length... at least as it pertains to electrical changes in the sound from the cable length. However, you would certainly notice acoustic delays. Sound travels very slow compared to the electrical signal in the cable.... roughly 1130 feet per second (depending on temperature and humidity), so we're looking at nearly a millisecond of delay per foot. Granted, the electrical properties of the cable (beyond it's resistance or impedance, such as capacitance and inductance) can alter the sound... after all a passive crossover network is merely capacitors and inductors.

You know, I just picked up the brand new Smaart 7 software... maybe this is a fun project to do in my spare time. ;) Let's see what kind of tangible measurements we can make in a DJ rig using different lengths of cable.

Ben
 
NLFX Pro said:
Well... you guys have left me little to say.... LOL... but I'll highlight a few points.... in any environment with some background noise, it's highly unlikely that you'll ever notice a difference of 50 to 100' in the cable length... at least as it pertains to electrical changes in the sound from the cable length. However, you would certainly notice acoustic delays. Sound travels very slow compared to the electrical signal in the cable.... roughly 1130 feet per second (depending on temperature and humidity), so we're looking at nearly a millisecond of delay per foot. Granted, the electrical properties of the cable (beyond it's resistance or impedance, such as capacitance and inductance) can alter the sound... after all a passive crossover network is merely capacitors and inductors.

You know, I just picked up the brand new Smaart 7 software... maybe this is a fun project to do in my spare time. ;) Let's see what kind of tangible measurements we can make in a DJ rig using different lengths of cable.

Ben
Click to expand...

"spare time",i didn't know that the words existed for Ben?? LOL!!
 
Thunder said:
Don't worry about 50 even 100 feet you nor anyone else is going to notice it!
Click to expand...

While Soundinmotion is, electronically, absolutely spot on, Steve has nailed the practical side of it. I've maxed at a 35 foot run, but that exceeds your need, and have had absolutely no issue- and that actually included an extension cable on one side. I was nervous as well, especially because it was last minute and I had to add that extension. It worked just fine though...
 
Other factors to consider:

Are the cable full time or part time cables?

Do the cables drink alcohol when working private, non-club events?

Does the signal seem caustic or unfriendly?

P.S. All the advice offered so far, except for mine, is worthy of consideration.
 
djrox said:
Other factors to consider:

Are the cable full time or part time cables?

Do the cables drink alcohol when working private, non-club events?

Does the signal seem caustic or unfriendly?

P.S. All the advice offered so far, except for mine, is worthy of consideration.
Click to expand...

Rox, did you get into JT's liquor cabinet? :sqlaugh::sqwink:
 
djrox said:
If you think I have to or would travel to Can of Duh for a toddy, you have obviously forgotten where I stay!:sqwink:
Click to expand...

Tell 'em Rox! :sqwink: The Big Easy is full o' liquor and lick-hers! :rofl:
 
I'm quite sure that if you used 5 feet of cable on one speaker, and used 100 feet on another (of adequate guage to carry the current, probably 12G for sure) you would find little, if any, measureable difference, and for sure no audible difference. The only difference you would be able to detect is the delay from the physical distance of the speaker itself. If you put the speakers side by side, I'm pretty sure no difference would be audibly detectable.

Big concerts regularly run 100ft or more cable to speakers all the time

I read mention about damping factor, which I have come to believe is not a deciding factor in keeping the wire short, even with heavy guage. If you want more details, I'll dig up the equations and resitances and you can calculate for yourself. To the speaker, an amp with a damping factor of 4000 isn't much different than an amp with 400 once you add some speaker cable in there.
 
NLFX Pro said:
Sound travels very slow compared to the electrical signal in the cable.... roughly 1130 feet per second (depending on temperature and humidity),
Click to expand...

To expand on this idea a little:

The speed of sound in an ideal gas (with a uniform molecular weight) is a function only of temperature. The temperature is measured on an "absolute scale" - either Kelvin or Rankine.

In air (which is not ideal), below 30,000ft in altitude, the speed of sound can be calculated accurately based on temperature. Above 30,000ft, the effect of gas composition (e.g. increasing amounts of ozone) require that the calculation include both temperature and pressure. These calculations are "close enough" for actual "rocket science" until the altitude reaches about 100,000ft (the "middle" of the stratosphere).

Humidity does have a very slight effect (less than 0.6%) on the speed of sound, because of the change in the molecular makeup of the gas. Water vapor displaces Nitrogen, Oxygen, and the other gasses that make up air, altering the molecular makeup of the gas. This different molecular weight has different properties relative to the propagation of sound.

NOTE: There is an "old wives tale" about humidity changing the "density" of the air, and that having an effect on the speed of sound. It is not true. A change in density would be met with an equal and opposite change in pressure that would cancel out any change in the local speed of sound.

In practical terms:
Indoors, the speed of sound can be treated as a function of temperature only. "Room Boom" (e.g. boundary conditions) will have a much larger effect on the sound propagation than any change in the speed of sound due to humidity.

Outdoors, the speed of sound can be treated as a function of temperature only. Wind currents will have a much later effect on the sound propagation then any changes in the speed of sound due to local atmospheric conditions.
 
soundinmotiondj said:
To expand on this idea a little:

The speed of sound in an ideal gas (with a uniform molecular weight) is a function only of temperature. The temperature is measured on an "absolute scale" - either Kelvin or Rankine. In air (which is not ideal), below 30,000ft in altitude, the speed of sound can be calculated accurately based on temperature. Above 30,000ft, the effect of gas composition (e.g. increasing amounts of ozone) require that the calculation include both temperature and pressure. These calculations are "close enough" for actual "rocket science" until the altitude reaches about 100,000ft (the "middle" of the stratosphere). Humidity does have a very slight effect (less than 0.6%) on the speed of sound, because of the change in the molecular makeup of the gas. Water vapor displaces Nitrogen, Oxygen, and the other gasses that make up air, altering the molecular makeup of the gas. This different molecular weight has different properties relative to the propagation of sound. NOTE: There is an "old wives tale" about humidity changing the "density" of the air, and that having an effect on the speed of sound. It is not true. A change in density would be met with an equal and opposite change in pressure that would cancel out any change in the local speed of sound. In practical terms: Indoors, the speed of sound can be treated as a function of temperature only. "Room Boom" (e.g. boundary conditions) will have a much larger effect on the sound propagation than any change in the speed of sound due to humidity. Outdoors, the speed of sound can be treated as a function of temperature only. Wind currents will have a much later effect on the sound propagation then any changes in the speed of sound due to local atmospheric conditions.
Click to expand...

so, is that a YES or a NO to the original question?

:sqconfused:
 
Holy smokes guys.... you crack me up. Since we're having science fair... here's the tortoise and the hare.

Sound = roughly 1128 feet per second (See SoundinMotion's clarification on that LOL)

Electricity = roughly 982,000,000 feet per second

You will likely never notice a DELAY from the length of cable. Far bigger concerns are loss, and potential alteration of the sound. However, I can tell you we often have runs in arenas, etc. that vary by more than a hundred feet and we have little work to do on the processing end.

Ben
 
Should we get into a discussion on whether the wire is solid or stranded? And the effects of skinning on the audio properties?

Let's not...

There is the difference, then there is what you can actually hear - even by the supposedly golden eared. In all actuality, given the noise floor at the typical event, even if there were a relatively minor change - people are not going to notice it.

Paralysis by analysis.
 
NLFX Pro said:
Holy smokes guys.... you crack me up. Since we're having science fair... here's the tortoise and the hare.

Sound = roughly 1128 feet per second (See SoundinMotion's clarification on that LOL)

Electricity = roughly 982,000,000 feet per second
Click to expand...


Got an "oops" in there Ben. Gotta post sober :sqlaugh:

Light travels at roughly 186,244 feet per second. You must have some of the fastest electricity around if it travels about 5,228 times as fast as light..:sqerr: I have to admit that I had a private event in the beginning of my Karaoke career that died almost that fast....:sqembarrassed:
 
You must log in or register to reply here.
Top Bottom
Back