speaker wire amperage????

[InVeNtOr]

if i have an emotiva xpa-5 with three output channels running @250w each, with the volume at around 70%, how much current would actually be running through a 12awg wire? i have an onkyo 805. i saw a simular question and an answer for it, but now i can't find it....so sorry for the double question.

i am just curious if i need to go to 10awg or would the 12awg be able to hand it easily. do think about cost into this answer....i can get all the wire i want for free at any gauge.

thanks for the input.

[LarryC]

i saw a simular question and an answer for it, but now i can't find it....

Dedicated circuit question....

[Guest " "]

The below is for AC audio...not to be confused with DC wire charts or electrical power grid 60hz transmission wire charts.

wire: current flow: total amp power: RMS power: 30 feet (15X2) .5 voltage drop

0 awg 334 amps 2763 watts
1 awg 265 amps 2193 watts
2 awg 210 amps 1740 watts
3 awg 167 amps 1381 watts
4 awg 132 amps 1096 watts
5 awg 105 amps 870 watts
6 awg 83.4 amps 690 watts
7 awg 66.2 amps 548 watts
8 awg 52.5 amps 435 watts
9 awg 41.7 amps 375 watts
10 awg 33.1 amps 273 watts

11 awg 26.3 amps 217 watts
12 awg 20.84 amps 172 watts
13 awg 16.54 amps 137 watts
14 awg 13.13 amps 109 watts
15 awg 10.42 amps 86 watts
16 awg 8.27 amps 69 watts
17 awg 6.56 amps 54 watts
18 awg 5.21 amps 43 watts
19 awg 4.13 amps 34 watts
20 awg 3.28 amps 27 watts
21 awg 2.60 amps 21 watts

[WMcD]

Not to argue with my friend Larry, but this seems to be a speaker wire question rather than a dedicated power (mains) question.

I'll get a little pedantic here to get closer to the real answer.

The current in the speaker wire pair is the same as in the speaker.

Very generally, we assume that the impedance of the speaker itself is somewhere around 8 ohms and we generally assume that it is purely resistive. To get a somewhat more accurate picture, we should include the resistance of the feed wire. That itself will change depending on the size of the wire and the lenght of the wire. Let's call it 0.1 ohm or less. That adds to make the loop impedance, or resistance 8.1 ohms.

Now, even with the above, let's assume the loop impedance is indeed 8 ohms. We still want to know the current in the loop. The loop is the circuit where current flows out of the amp through one speaker wire, through the speaker, and back to the amp through the other speaker wire. And the current flows through the amp (and we'll assume it has zero impedance.)

Ohm's law tells us that R = V/I. Where R is the resistance, V is the applied voltage (from the amp). And I is the intensity of the current flowing.

It is interesting to see that R is not really a quantity, rather it is ratio of voltage to current. But in any case, it shows that if 8 volts are applied by the amp to 8 ohms, 1 amp flows. If 16 volts, then 2 amps, etc.

You may appreciate that by saying we have an amp rated at 100 watts or whatever, does not tell us the voltage at the output terminals. That voltage is varying in time to the music. And the waveform in time is ragged.

A starting point is to imagine we're using a sine wave and, by some means, we see the sine wave has peak (and valley) at 8 volts. This means the current in the loop is another sine wave with peaks and valley of 1 amp. A pure resistive load causes the current to be a scaled version of the applied voltage.

You can imaging the music has a wiggly ragged voltage waveform in time (which is the fact). The current in the wire is again, just a scaled wiggly ragged waveform which is the same pattern (shape in time). This may be an under appreciated principle. Ohms law works with waveforms presented in time just as with simple numbers for voltage and current.

The answer about current overall, is, "it depends". Most of "it depends" is that it depends on how much voltage your amp is putting out. 8 volts can be pretty loud with Klipsch speakers.

Wm McD

[InVeNtOr]

i responded to that dedicated circuit question, not what i was intending.

i guess what i am trying to ask is what would be the most amps that will be passing thought my 12awg wire when my volume is at 70% with a 250w amp? it almost seems like its a question that is almost impossible to answer because it's varing too much. i am really only interested in the peak value so i can get the right size wire. my wire runs for my mains are less than 15' and my center is around 7'.

i may stick with some 12awg twisted pair for ease of insulation. i don't have any 10awg twisted, i would have to do the twisting myself, guess i am too lazy to do so....lol

[Guest " "]

Gil

You're basically correct at one given frequency and typically lower frequencies behave closer to the DC wire principles being applied.

If we say that using DC wire theory that a given run of wire has a .1 ohm resistance, the impedeance of the wire increases as frequency increases. This is why a 4 ohm woofer DC's at 3.4 ohms, a 16 ohm mid driver DC's at 11 ohms and an 8 ohm tweeter DC's at 6 ohms.

So wire sizing has to consider gauge, lenth, operating frequency and voltage drops at the various operating frequencies.

Folks have trouble with this when they compare 300 strand 10 gauge monster cable to 76 strand 14 guage lamp cord. From a DC perspective the data will suggest little difference.

[Guest " "]

i guess what i am trying to ask is what would be the most amps that will be passing thought my 12awg wire when my volume is at 70% with a 250w amp?

12 awg 20.84 amps 172 watts

Using 12 awg would put you within 5% of your goal for a 15 foot paired run (30 ft total) with no more that .5 voltage drop from 20hz - 20khz

[Islander]

if i have an emotiva xpa-5 with three output channels running @250w each, with the volume at around 70%, how much current would actually be running through a 12awg wire?

Keep in mind that 70% on the volume control does not necessarily mean 70% of 250 watts. It more likely means 70% of the amp's possible volume. If you have a low-voltage input, say .1V, you'll get a certain output in watts, and if you have a higher-voltage input, say 1V, you'll have a much higher output in watts.

Amplifiers don't actually make power, they multiply the power that's supplied to them.

[InVeNtOr]

speaker, so you are saying that 12awg is almost too small and i should move up to 10awg?

[WMcD]

Gosh, I'd say that 12 gauge is more than thick enough.

Continuing through here. The volume knob setting has an effect of course. But consider that if the music is silent, you're getting zero volts,amps, and power even at full rotation of the volume knob.

Some test CD's have a band with max recording output (typically 1 kHz) which I suppose is a sine wave with the peak at all 16 bits "on." So that would be the max that any music CD would put out on peaks, and you could determine how much voltage your amp is putting out at any volume knob twist or display read out.

This must be done with great care. My guess is that you'll find that low to moderate settings are very loud. The test CD's have warnings which must be taken seriously.

Wm McD

[pauln]

Here is what I get using P=V^2/R and I=V/R

Watts	ohms	Volts	Amps
2048.000	8	128.00	16.00
1024.000	8	90.51	11.31
512.000	8	64.00	8.00
256.000	8	45.25	5.66
128.000	8	32.00	4.00
64.000	8	22.63	2.83
32.000	8	16.00	2.00
16.000	8	11.31	1.41
8.000	8	8.00	1.00
4.000	8	5.66	0.71
2.000	8	4.00	0.50
1.000	8	2.83	0.35
0.500	8	2.00	0.25
0.250	8	1.41	0.18
0.125	8	1.00	0.13
0.063	8	0.71	0.09
0.031	8	0.50	0.06
0.016	8	0.35	0.04
0.008	8	0.25	0.03
0.004	8	0.18	0.02
0.002	8	0.13	0.02
0.001	8	0.09	0.01

[kouack]

Your chart makes more sense, because with the other chart what the pro would be using for a 18k watts amp like powersoft 20k or a Labgrupen PLM14000 of 14k watts a 0000 awg? totally unpractical and never seen 0 gauge for speaker.

Here is what I get using P=V^2/R and I=V/R

Watts	ohms	Volts	Amps
2048.000	8	128.00	16.00
1024.000	8	90.51	11.31
512.000	8	64.00	8.00
256.000	8	45.25	5.66
128.000	8	32.00	4.00
64.000	8	22.63	2.83
32.000	8	16.00	2.00
16.000	8	11.31	1.41
8.000	8	8.00	1.00
4.000	8	5.66	0.71
2.000	8	4.00	0.50
1.000	8	2.83	0.35
0.500	8	2.00	0.25
0.250	8	1.41	0.18
0.125	8	1.00	0.13
0.063	8	0.71	0.09
0.031	8	0.50	0.06
0.016	8	0.35	0.04
0.008	8	0.25	0.03
0.004	8	0.18	0.02
0.002	8	0.13	0.02
0.001	8	0.09	0.01