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Discussion Starter #1
hi guys, question, i need to power up 2 amps for my car:

1 will take 4x120 rms (Vibe Audio Space SpaceBox S4 SpaceBox Stereo 4 Channel )
1 will take 400 rms (sub) (KW-2270 +KW2v8 rainbow Kraftwerk 2ch amp)

how big should be the power wire?

can i run one wire from battery (4AWG?) or i need to put 2 wires like that??
 

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You can use this wire calculator at BCAE--


scroll down until you find the calculator, thought her tis LOTS of other useful wire info there as well
 

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hi guys, question, i need to power up 2 amps for my car:

1 will take 4x120 rms (Vibe Audio Space SpaceBox S4 SpaceBox Stereo 4 Channel )
1 will take 400 rms (sub) (KW-2270 +KW2v8 rainbow Kraftwerk 2ch amp)

how big should be the power wire?

can i run one wire from battery (4AWG?) or i need to put 2 wires like that??
I can't find much info on the Vibe amp, but the KW-2270 looks like it takes 4 gauge wire. The Vibe amp might take 4 gauge as well or could be 8? I would probably run 1/0 to a distribution block and then run 4 gauge from the block to the amps. You probably could get by with just 4 gauge, but I like to be on the safe side. And if you ever went to anything more powerful you'd already have the 1/0 run.
 

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Discussion Starter #4
i have 2 4 gauge wires, so now just thinking to put both or leave one to other car :)

because i will not listen music 100% i will do 20-30% and some times 60%, so dont think
will be such a big load on that wire
 

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i have 2 4 gauge wires, so now just thinking to put both or leave one to other car :)

because i will not listen music 100% i will do 20-30% and some times 60%, so dont think
will be such a big load on that wire
Depending on the length of the run, I believe I saw on Crutchfield's calculator where you can run about 150 amps on 4 gauge wire. That Rainbow amp had two 25 fuses. I can't imagine the Vibe amp would be using much more than 50 itself.
 

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To put it into perspective I am running 1/0 power and ground to the rear of my vehicle, my main power fuse on the wire is 150amps. I am running 2 four channel amps with 40 amp fuses on each (these amps are class A/B) as well as the 120 amps of fusing on my monoblock plus whatever power the MS-8 requires to run. I have never blown the 150 amp fuse.
 

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Assume your battery voltage is 14v
Current=Power/Voltage
(120x4)/14=34 Amps
400/14=28.5 Amps
60-65 Amps.
One 4 gauge wire is fine.


To put it into perspective I am running 1/0 power and ground to the rear of my vehicle, my main power fuse on the wire is 150amps. I am running 2 four channel amps with 40 amp fuses on each (these amps are class A/B) as well as the 120 amps of fusing on my monoblock plus whatever power the MS-8 requires to run. I have never blown the 150 amp fuse.
The current draw is what is most important.
 

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i have 2 4 gauge wires, so now just thinking to put both or leave one to other car :)

because i will not listen music 100% i will do 20-30% and some times 60%, so dont think
will be such a big load on that wire
It doesnt matter how often you listen to music. If you, or anyone else driving the car, turns the volume to max the amplifiers will be drawing that 65 amps of current instantly and immediately. If the electrical system is not done properly, the fuses will blow, or worse, electrical fire. But you will be fine with 4 gauge.
 

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This is the second post in as many days which involves a diyer explaining that they wont turn the volume up on their stereo; as if their friend, mechanic, child, significant other, etc. will never touch the stereo.

It does not matter how YOU will use the system, or how often you listen, it needs to be safely installed.

High current through too small a wire generates heat. Heat creates electrical fires. The wires run under and around flammable things like carpet.

The instant the volume knob goes up, the amplifier is drawing the current. There is no delay. The wire will take some time to heat, yes. Hours, days, years... who knows....of charring the insulation until it flashes.

This is called Joule Heating.

The heat produced is based on the current drawn and the resistance. Longer wires have more resistance. Smaller wires have more resistance.

More resistance means less power going to the amplifier as well. This will reduce the output of the amplifier.

So from a performance and safety aspect, you consult the chart and pick the gauge. Now you know why distance and current draw determine the wire size. Resistance.

And install fuses as appropriate based on the amplifiers max current draw and you can use the formula in my previous post above for that. Properly sized fuses are VERY important.

And again, you dont set it up based on how you plan to use it. You make it safe. It is YOUR responsibility. Engineers who design for a living always try to do things this way to make them safe for everyone.
 

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This is the second post in as many days which involves a diyer explaining that they wont turn the volume up on their stereo; as if their friend, mechanic, child, significant other, etc. will never touch the stereo.

It does not matter how YOU will use the system, or how often you listen, it needs to be safely installed.

High current through too small a wire generates heat. Heat creates electrical fires. The wires run under and around flammable things like carpet.

The instant the volume knob goes up, the amplifier is drawing the current. There is no delay. The wire will take some time to heat, yes. Hours, days, years... who knows....of charring the insulation until it flashes.

This is called Joule Heating.

The heat produced is based on the current drawn and the resistance. Longer wires have more resistance. Smaller wires have more resistance.

More resistance means less power going to the amplifier as well. This will reduce the output of the amplifier.

So from a performance and safety aspect, you consult the chart and pick the gauge. Now you know why distance and current draw determine the wire size. Resistance.

And install fuses as appropriate based on the amplifiers max current draw and you can use the formula in my previous post above for that. Properly sized fuses are VERY important.

And again, you dont set it up based on how you plan to use it. You make it safe. It is YOUR responsibility. Engineers who design for a living always try to do things this way to make them safe for everyone.
And yet you just told him it was ok while not allowing for the efficiency of the amplifiers, or voltage drop at all, try the numbers again with maybe 70% efficiency (80-85 for class d) and 13v then see what your current figures come to, I have no issue with people giving advice if it’s sound advice

generally class d 1000w is 100a, so 400w is 40a and ab it’s more like 800w is 100a so if you said 55-60a for the 480w rms and around 100a total you’d be more like, personally if it’s a run down the length of a small hatchback, say 4m I’m ok with 4g, but if it’s a big estate or a 4x4 and it’s 5-5.5m I’d rather err on the side of caution and run 1/0 gauge or as he has, 2 runs of 4 gauge if I had it kicking about

Fuse the long runs at 50a a piece (the fuse protects the cable it does nowt for the amp, if that goes short the damage is done which then blows the fuse, but if it’s two runs with reduced current draw I will reduce the fuse size also just because I can)
 

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Im usually more polite and eloquent when I disagree with someone... oh, and I actually give an explanation instead of sounding like one of the Kardashians.
His point is you made a blanket statement... which is very wrong also, most music is recorded at -6db at most, that’s a good chunk less than full current draw... if and only if the music contained full on sine waves, as most music is dynamic, ie it goes up and down in level, on top of the -6db there is also the reduction due to these dynamics, if an amplifier is fused at 40a and it’s worst case a well setup bass amplifier then the current won’t go much past 15-20a even if turned up full, it just won’t happen, if you played a 0db sine wave then you would see the 40a current draw, but who sits in a vehicle and whacks a sine wave up to full pelt for fun
 

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Another way to work it out is to add up what all the amps fuses are.
If the current draw exceeds the fuse rating then the fuse will eventually blow.

If one is adding up n channels of watts then they may want to divide by 12V, but that still assumes that a Class-A and Class-D have equal efficiency.

No matter what math and efficiencies are in vogue, just using the fuse ratings seems to be the simplist method to use.
 

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Discussion Starter #15
thx guys for so much info, yes iam right that it should be dont on how amp can use the energy not how i listen to music ;) i just sad it because i didnt know if it makes difference if i lissen to music 3h on max or just all the time 60% and only some times for one song put 100%.

i have 2 amps:
vibe is: 2x25A
rainbow (for sub) is: 2x30A
 

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thx guys for so much info, yes iam right that it should be dont on how amp can use the energy not how i listen to music ;) i just sad it because i didnt know if it makes difference if i lissen to music 3h on max or just all the time 60% and only some times for one song put 100%.

i have 2 amps:
vibe is: 2x25A
rainbow (for sub) is: 2x30A
single 4ga with a distribution block to split 2 8ga ( or 4ga if the amps will accept ) wires to the 2 amps is more than enough.
 
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