help with car audio installs

Invigor · #1 10-18-2005, 05:32 PM

i was thinkin the other day that my house wire at 110v is 14 guage and can handle 15amps...translated, that's like 1500watts of electricity. what I cannot understand is why amplifiers in cars needs like 4 guage at a minimum for say like 500watt amplifiers...sure 14.4volts into 500watts is 35amps, but is it absolutely necessary to have such huge wire??

jws444 · #2 10-18-2005, 06:43 PM

I think you just answered your own question! 35 amps is a huge load so yes, a 4 or 8 guage wire is a good choice especially when it needs to be run a whole car length too. The last thing you'd want is for the wire to heat up and make a car-b-que. Also have to take into account the amp's peak power output. Peaks can easily be 10x the power needed, even though for very short moments. Usually this is well beyond clipping, and can cause problems with the amp and the car's electrical system. It's just that most people have no clue this is happening.

BMW Rider · #3 10-18-2005, 10:11 PM

To handle that level of current draw you would need at least 10 guage wire, assuming the amp was close to the power source. The longer the run, the more power loss thus the need for heavier wire. Usually the amp is mounted in the trunk while the battery in most vehicles is in the front. Thats a long run of wire and will result in power loss and overheating of the wire if it is too light. I would also strongly reccomend using a fuse or fused link at the power source to protect the circuit in case of a short. I've seen more than a few cars burnt to the ground due to bad stereo installations.

Tarolisol · #4 10-18-2005, 11:02 PM

Not that this has any bearing on this, but when i used the wrong wire for testing my subs i used 8 gauge. It sounded horrible when i switched to the proper 1 gauge wire which is HUGE it sounded so much more powerful.

Gizmo · #5 10-19-2005, 01:42 AM

12vDC has a much worse line loss coefficient than 120vAC. 12vDC can lose up to 1.5v in as little as 4' dependent on the current draw. Just an off the scale example. This is why they run 500,000VAC from the power plant to a city substation, the higher the voltage, less current required, and thus less line loss. If you had a car amp pulling 40+ amps u would end up with a higher voltage drop than a trunk light running at a quarter of an amp.

Invigor · #6 10-19-2005, 04:03 AM

Quote:

Originally Posted by Gizmo

12vDC has a much worse line loss coefficient than 120vAC. 12vDC

that's kinda the idea i had brewing in my mind, didn't know if it was true or not..I guess it is

thanks for the replies

BMW Rider · #7 10-19-2005, 03:53 PM

The simplest way to understandthe relationship between voltage and amperage is to think of it in terms of water flow. Voltage is pressure, amperage is volume. More pressure(voltage) = more volume(amperage) for the same size pipe(wire). Thus, less pressure at the same volume means you need a bigger pipe. The longer the pipe, the higher the head loss, the lower the flow.