Where I play it is not unusual to have 1,000 feet of ten gauge wire driving an actively cross overed loudspeaker. I try to explain to folks that electrical code depending on exact wiring methods only permits 10 or 12 gauge wire to be used.
Although that matters for the low frequency section it doesn't for the high frequencies. Even with a crossover frequency as low as 800 hertz, the atmospheric absorption of high frequencies often requires more than 10 dB of boost at 8,000 hertz.
14 gauge wire costs 35% of the cost of 10 gauge and has the same effective loss. Unfortunately I have yet to meet a sound system consultant who understands this! They do know by measurement that there is a lot of high frequency roll off, but attribute it all to atmospheric losses.
Although that matters for the low frequency section it doesn't for the high frequencies. Even with a crossover frequency as low as 800 hertz, the atmospheric absorption of high frequencies often requires more than 10 dB of boost at 8,000 hertz.
14 gauge wire costs 35% of the cost of 10 gauge and has the same effective loss. Unfortunately I have yet to meet a sound system consultant who understands this! They do know by measurement that there is a lot of high frequency roll off, but attribute it all to atmospheric losses.
14 gauge wire: 1.63mm diameter, 2.08mm2 section, 8.29 Ohm per Kilometer.
10 gauge wire: 2.59mm diameter, 5.26mm2 section, 3.28 Ohm per Kilometer.
14 gauge wire versus 10 gauge wire is 2.5 times more resistive.
1000 feet is 2.5 ohm versus 1 ohm.
10 gauge wire: 2.59mm diameter, 5.26mm2 section, 3.28 Ohm per Kilometer.
14 gauge wire versus 10 gauge wire is 2.5 times more resistive.
1000 feet is 2.5 ohm versus 1 ohm.
Resistance is at DC. Skin effect is an AC issue. Guess what the added impedance is at 8,000 hertz?
If the plait is equivalent to a tight twist (which I doubt) then it will be quite good at rejecting RF. You have simply spent extra time making a cable which looks nice. If it is not equivalent to a tight twist then you have spent time making a cable which performs worse than a much simpler cable. Fortunately in many cases RF rejection is not required.tapestryofsound said:
Plaiting for audio cables is surprisingly popular; it looks nice, but has no special electrical properties and in many cases it will be inferior to a simpler arrangement. I cannot think of any circumstances in which it might be better than a simpler arrangement.
14 gauge wire: 1.63mm diameter, 2.08mm2 section, 8.29 Ohm per Kilometer.
10 gauge wire: 2.59mm diameter, 5.26mm2 section, 3.28 Ohm per Kilometer.
14 gauge wire versus 10 gauge wire is 2.5 times more resistive.
At 8 KHz the skin effect is 1mm deep.
So, there is no change from DC to AC for the 14 gauge wire.
There is a small increase for the 10 gauge wire, it's cross section is lowered to 4.54mm2, an increase of it's resistance x 1.16
About a 1000 feet câble ( 2000 feet wires )
14 gauge wire R is 5 ohm at DC and 8KHz
10 gauge wire R is 2 ohm at DC and 2.32 ohm at 8KHz
A do not know the impedance of your speakers. Assuming 8 ohm, I end up with:
14 gauge wire gives a 4.22dB loss at DC and 8KHz
10 gauge wire gives a 1.94dB loss at DC and a 2.21dB loss at 8KHz
Conclusion: Assuming a 1000 feet cable and 8 ohm speakers
With a 14 gauge wire cable the loss is 4dB.
With a 10 gauge wire cable the loss is 2dB, skin effect makes an additional loss of 0.3dB at 8,000 Hz.
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Some topics need to die...Don't punish them with some more years in bed!
The only benefit i get from this topic is the fact that i've learned that instead of 2.5mil solid wire , i might use 2.5mm hollow extruded wire, but i can't find anybody to make the hole ...
Now seriously:
Will i be able to replace 2.5mm solid wire with 0.25mm litz wire in a system that outputs 150 w /8 ohm?
Or should i leave the holes transporting the base and the electrons for the highs and mids? What should i do?
I think i know the answer:
I should make one more high end audio cables company.The investment (chinese cheap wires)is small, the output is really high as i see it.
Should i tell you that the Chinese shops sell also very high end cables for cheap?
Most of the electric wires are aluminium wires covered with a thin layer of copper...They also sell it as litz wire...hundreds of thin coppered aluminium wires.
Aluminium is also light so the aluminium electrons are also light and they travel faster 🙂)) there's a great chance that the aluminium electrons will transport the base and the heavy copper electrons the highs...ahhh...so the base will travel faster and keep up with the highs...That's a better theoretical model 🙂
God keep Chinese alive for more aluminium wires covered in copper!
No...I won't tell you this.I'll keep this secret for me!!!
The only benefit i get from this topic is the fact that i've learned that instead of 2.5mil solid wire , i might use 2.5mm hollow extruded wire, but i can't find anybody to make the hole ...
Now seriously:
Will i be able to replace 2.5mm solid wire with 0.25mm litz wire in a system that outputs 150 w /8 ohm?
Or should i leave the holes transporting the base and the electrons for the highs and mids? What should i do?
I think i know the answer:
I should make one more high end audio cables company.The investment (chinese cheap wires)is small, the output is really high as i see it.
Should i tell you that the Chinese shops sell also very high end cables for cheap?
Most of the electric wires are aluminium wires covered with a thin layer of copper...They also sell it as litz wire...hundreds of thin coppered aluminium wires.
Aluminium is also light so the aluminium electrons are also light and they travel faster 🙂)) there's a great chance that the aluminium electrons will transport the base and the heavy copper electrons the highs...ahhh...so the base will travel faster and keep up with the highs...That's a better theoretical model 🙂
God keep Chinese alive for more aluminium wires covered in copper!
No...I won't tell you this.I'll keep this secret for me!!!
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You need to know the insulation thickness to calculate the inductance, as conductor spacing is important.
All the calculations I see here neglect the proximity of the return conductor.
This is a simple test that can be done on a 1000 foot spool of cable as long as you have access to the inner end.
Just short the end, run Ls /Rs vs frequency out to 20K.
Jn
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Yes, I don't know how to calculate it with insulation, I guess it acts like a capacitor... maybe I can pretend the wires are in fact a capacitor and calculate for the spacing and insulation type?
The skin depth effect at 20khz is 460 uM it should not do anything alone to the frequency response... removing a cross section of 0.001mm of a wire gage has almost no effect on its inductance right?
The skin depth effect at 20khz is 460 uM it should not do anything alone to the frequency response... removing a cross section of 0.001mm of a wire gage has almost no effect on its inductance right?
460µM is 0.46 mm
Skin effect decreases inductance a little bit ( Wikipedia gives it's calculation Skin effect - Wikipedia )
This calculator gives inductance for two wires at some distance ( twin lead ) https://technick.net/tools/inductance-calculator/
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The inductance is a function of the aspect ratio of conductor diameter to conductor spacing. For example, if you examine two 10 awg wires, one insulated with teflon to 300 volts, the other insulated with pvc to 2kv, the pvc wire will have a higher inductance because the insulation changes the spacing of the conductor.
Also neglected in Ed's scenario is how the cables are run. I assume that a stadium does not run the wire on the ground across the infield, so there will be either tray or conduit involved. 1000 feet of twisted pair in a conduit....expect the metals of the conduit to have an effect.
The only way to determine if it is skin/proximity or conduit effects is to perform the proper measurements. I assume Ed won't do that, as it's of no value to the install anyway. He has code to deal with.
John
Yes, but could we have estimates ( based on usual cables and routed on the ground ).
Some of these pages, they drive me nuts.
mu/8pi is the internal inductance of a cylindrical wire. Why oh why can't they just say 50nH per meter or 15 nH per foot??? Why make us do the math????
4 pi 10e-7 / 8 pi = .5 10e-7 H/meter, 50 nanohenries per meter,
I use 15 nH per foot for wire internal inductance.
jn
sigh..
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I don't know if Ed segregates wires based on function, or if he mixes power, speaker, and voltage and has to calc ampacity of the speaker runs.. so I can't guess how he fills conduit. So the install effects could change based on how he runs the wires.
I am allowed to engineer my installs based on engineering calculations, I just clear it with the AHJ first.
jn
JN,
Actually you have to unspool the cable to get accurate measurements. Spooled you get above 2 mH per 1000' of cable of any gauge I have around. In field measurements of the loudspeakers' near field the HF is down by 6-8 dB from just the cable runs.
If you actually had the full 2 mH into a 16 ohm compression driver you would be down by 16 dB at 8,000 Hz. There really is a reason in most of the older loudspeaker systems the compression driver was 16 ohms and not 8 ohms as was the low frequency driver.
BTY we use tray with no power cables in sight. There are some other design features you would understand, but I see no reason to get into them.
Turns out the design of loudspeaker cable is not trivial resistance limited once you start getting longer than about 50 feet and full range to 20,000 Hz.
Actually you have to unspool the cable to get accurate measurements. Spooled you get above 2 mH per 1000' of cable of any gauge I have around. In field measurements of the loudspeakers' near field the HF is down by 6-8 dB from just the cable runs.
If you actually had the full 2 mH into a 16 ohm compression driver you would be down by 16 dB at 8,000 Hz. There really is a reason in most of the older loudspeaker systems the compression driver was 16 ohms and not 8 ohms as was the low frequency driver.
BTY we use tray with no power cables in sight. There are some other design features you would understand, but I see no reason to get into them.
Turns out the design of loudspeaker cable is not trivial resistance limited once you start getting longer than about 50 feet and full range to 20,000 Hz.
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Somebody said the even litz wire is useless for this...I wonder what all the audiophile world have to say about their thousands of pounds being thrown out on the most expensive headphones with their 3 meters , very thin, long cables...
For frequency accuracy check, all the mastering engineers use headphones, some of them being very expensive but all of them use tha same long litz wires...
Now they found out that the whole audio industry betrayed them...They couldn't hear the magnetron in the microwave oven and the house is now on fire!
Should we call 112 , 911, 119 or 101 ?
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