SPEAKER WIRE = 14 AWG or 12 AWG? - Page 4 - AVS Forum | Home Theater Discussions And Reviews
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post #91 of 104 Old 07-26-2015, 10:29 AM
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Originally Posted by Bill Fitzmaurice View Post
Look up the definition of 'inaudible'. If the insertion loss of 14ga. is inaudible then using 12ga. can't make it more inaudible. In most average applications even 16ga has inaudible insertion loss.
Dang, Bill, you make me feel like I'm an idiot.
Plain English, please. Say with the same setup, if I run 20ft speaker wire to a rear speaker, one with 12-awg wire, another with 14-awg one. Which one is better?
Now, with the same setup, if I run 200ft long, which one is better?
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post #92 of 104 Old 07-26-2015, 02:10 PM
 
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Originally Posted by tinhvo View Post
if I run 20ft speaker wire to a rear speaker, one with 12-awg wire, another with 14-awg one. Which one is better?
Neither. Assuming 4 ohm speakers, which is worst case, 14ga insertion loss will be 0.22dB. You can't hear an insertion loss of 0.22dB. With 12ga insertion loss will be 0.14dB. You can't hear 0.14dB insertion loss, but since you can't hear 0.22dB insertion loss either you've not accomplished anything with the larger gauge. With a 20 foot run into a 4 ohm load you want an insertion loss of less than 1dB. All you need to do that is 18ga, which has a loss of 0.53dB. You'd only need larger than 18ga if you had more than 100 watts continuous output, which would be very rare into rears, and then it would be for current capacity, not insertion loss. With higher than 4 ohm impedance speakers the gauge requirements are lessened.
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Now, with the same setup, if I run 200ft long, which one is better?
Neither. 200 feet is too long, as inductance and capacitance both become problematic, and they're not cured with a larger gauge. I wouldn't use even 100 feet. If you must go that long you should use a 70 volt system.
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post #93 of 104 Old 07-26-2015, 07:14 PM
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Originally Posted by Bill Fitzmaurice View Post
Neither. Assuming 4 ohm speakers, which is worst case, 14ga insertion loss will be 0.22dB. You can't hear an insertion loss of 0.22dB. With 12ga insertion loss will be 0.14dB. You can't hear 0.14dB insertion loss, but since you can't hear 0.22dB insertion loss either you've not accomplished anything with the larger gauge. With a 20 foot run into a 4 ohm load you want an insertion loss of less than 1dB. All you need to do that is 18ga, which has a loss of 0.53dB. You'd only need larger than 18ga if you had more than 100 watts continuous output, which would be very rare into rears, and then it would be for current capacity, not insertion loss. With higher than 4 ohm impedance speakers the gauge requirements are lessened.
Neither. 200 feet is too long, as inductance and capacitance both become problematic, and they're not cured with a larger gauge. I wouldn't use even 100 feet. If you must go that long you should use a 70 volt system.
Alright, so the more insertion loss, the worse it gets? Anything less than 1dB loss, is neglect-able? So technically, the wire with 0.14dB loss is better than one with 0.22dB?
As for inductance/capacitance, which wire has higher value?
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post #94 of 104 Old 07-26-2015, 08:07 PM
 
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Originally Posted by tinhvo View Post
Alright, so the more insertion loss, the worse it gets? Anything less than 1dB loss, is neglect-able? So technically, the wire with 0.14dB loss is better than one with 0.22dB?
If you can't hear less than a 1dB loss why would you think you can hear the 0.08dB difference between 14 and 12ga? I'm beginning to feel like a dog chasing his own tail here.
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As for inductance/capacitance, which wire has higher value?
That's not predictable from the gauge. But as it can be pretty much assumed that inductance and/ or capacitance is going to be problematic with long lengths, over 50 feet or so, the blanket recommendation is don't use more than 50 foot speaker cables unless it's in a 70v system.
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post #95 of 104 Old 07-26-2015, 09:36 PM
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OK, so with 45ft long, which wire has higher value of inductance/capacitance? or it isn't predictable for all gauges?
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post #96 of 104 Old 07-27-2015, 06:30 AM
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Originally Posted by enlisted23 View Post
Now I'm wondering if there would be any benefit for an in-wall run to use stranded speaker wire instead of solid core 14/2 or 12/2 residential wire?
I'd assume that the solid wire would have lower DC resistance than equivalent gauge stranded wire.
The main difference is solid wire is more likely to snap and create an open circuit. Once you get a small crack at a bend, the crack can quickly propagate all the way through. With stranded, the strand would just break leaving the other stands untouched. Stranded is more likely to short than solid since a single stand is more likely to find it's way to the other side than an entire solid wire.
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post #97 of 104 Old 07-27-2015, 06:41 AM
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Originally Posted by Bill Fitzmaurice View Post
Quote:Originally Posted by KidHorn 

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Look at what gauge wire your electrical system in your house uses. It can handle way more current than anything you would ever push to a speaker.
The current requirement for speaker cable can be considerably higher than that for the power supply cable. If the amp is drawing 1000 watts at 110v that's 9 amperes. Assuming 70% efficiency that amp could put out 700w, which into a 4 ohm load is 52 volts at 13 amps. The wire gauge requirement in this case would be 16ga. for the A/C supply, 14ga. for the speaker cable. If the load was 2 ohms, often seen in pro-sound, 700w would be 37 volts at 19 amps, requiring 12ga speaker cables.
OK, but the electrical wire that powers an amp has to be able to handle significantly more current than anything you would drive through a speaker wire from said amp. Unless your amp has a built in generator .
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post #98 of 104 Old 07-27-2015, 08:00 AM
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Originally Posted by KidHorn View Post
OK, but the electrical wire that powers an amp has to be able to handle significantly more current than anything you would drive through a speaker wire from said amp. Unless your amp has a built in generator .
Huh?
No, the amp gets it's electrons back from the speaker so the current can be larger than what it gets from the wall outlet. It's the power that can't be larger.

Read what Bill said again.

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post #99 of 104 Old 07-27-2015, 08:45 AM
 
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Originally Posted by psgcdn View Post
the current can be larger than what it gets from the wall outlet. It's the power that can't be larger.
Read what Bill said again.
+1, this is a very basic Ohms Law calculation. For equal power as voltage goes down current goes up. For equal power as load impedance goes down current goes up.
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post #100 of 104 Old 07-27-2015, 10:19 AM
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Originally Posted by Bill Fitzmaurice View Post
+1, this is a very basic Ohms Law calculation. For equal power as voltage goes down current goes up. For equal power as load impedance goes down current goes up.
Technically, it's possible, but you would have to have a lot of current going to a single speaker and only that speaker. Not a likely scenario. More likely the power would be more evenly distributed across 5 or 7 speakers. It's extremely unlikely your speaker wire would ever need to be a thicker gauge than the wire that supplies power to your amp. For safety reasons. Not audible reasons.
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post #101 of 104 Old 07-27-2015, 11:15 AM
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Lots of speakers have low impedance dips at low power-hungry frequencies. What power does it take to equal the 9-amp current draw from the example above at 2.9 ohms? 235 Watts. Not unheard of.

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post #102 of 104 Old 07-27-2015, 12:09 PM
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You need to know more about the wire than just the AWG to calculate inductance and capacitance. It depends upon the insulator thickness/wire spacing and insulation material, among other things. However, for typical twin lead used for audio speaker cables, I have usually measured around 15 ~ 25 pF/ft (a bit higher than the Wikipedia article) and 0.1 ~ 0.2 uH/ft (about the same as Wikipedia).

https://en.wikipedia.org/wiki/Speaker_wire

I don't understand the safety reference with regards to speaker wire. IME it is fairly common for the speaker wire to be heavier than the power cord, partly to keep the output impedance low (damping factor high, if you prefer), as well as to mitigate loss. 100 W into 4 ohms is 5 Arms and 20 Vrms; into 8 ohms, the math works out to 28.28 Vrms and 3.54 Arms. From the wall socket, providing steady 120 Vrms, you only need 1.2 Arms for that same 100 W. There will be losses, natch, but wall current is still lower than what is going into the speaker.

Current spikes from the wall do occur, but the power supply has large storage (decoupling) capacitors to provide short high-current bursts and reduce the input current spikes. The output impedance of most SS amplifiers is much lower the wall outlet to help control the speakers (hand waving). Many speakers exhibit low impedance at one or more points in their frequency response and thus have high-current demands at those frequencies.

HTH - Don

"After silence, that which best expresses the inexpressible, is music" - Aldous Huxley
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post #103 of 104 Old 07-27-2015, 12:27 PM
 
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Originally Posted by DonH50 View Post
wall current is still lower than what is going into the speaker.
That will usually be the case, as the supply is 110v, while 100 watts into a 4 ohm load is 20v. Thus a draw of 200w from the wall is 1.8 amperes, while a 100w draw from the amp output is 5 amperes.
The only commonplace instance where the power supply wire must be of an equal or larger gauge than the speaker wire is in auto sound, where it's not unusual for the supply current to exceed the output current. That's because the supply voltage is only 14.8v nominal, so it will draw nearly eight times the current for the same power as an amp on a 110v supply.
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post #104 of 104 Old 01-15-2016, 08:23 AM
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This was an amusing thread to read. I came on asking the same questions and 45 minutes later is seems like it doesn't matter, lol. I guess 14 gauge it is. Thanks!
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