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Wire Sizes

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Member - Posts: 33
Member spacespace
Joined: October 30, 2014
Location: Maine, United States
Posted: July 17, 2015 at 3:39 PM / IP Logged Link to Post Post Reply Quote mohpro
I have an Alpine MRP-F250 4 channel amp powering my speakers and a kenwood kac-9103D amp powering my pair of subwoofers. The mrpf250 puts out 40W RMS per channel for a total of 200W RMS. The kenwood puts out 500W RMS. My question is will 4 gauge wire be the proper size wire for this system? Can i run 4 ga. From the battery to a distro block, then 4 ga. from the distro block to both amps? will this be the right size wire, or.can i run 8 ga. From the distro block to the alpine and 4 ga. From the distro to the kenwood? Pretty sure either above mentioned setup will work but just wanted a second opinion.
Member - Posts: 17
Member spacespace
Joined: July 14, 2015
Location: Indiana, United States
Posted: July 17, 2015 at 8:33 PM / IP Logged Link to Post Post Reply Quote knudsen
Hi Mohpro,
"40W RMS per channel for a total of 200W RMS"
I think that would be:
50W RMS per channel for a total of 200W RMS
40W RMS per channel for a total of 160W RMS
That's mute, because either way, you are above 400 watts and below 600 watts on the chart:
Minimum size depends on the length of the wire and the amperage (watts/12, but the handy chart shows it in watts so you don't need to divide). The only drawback of larger wire is $$$ and a bit more difficulty in running/routing and terminating the ends. Well, there's also the constant temptation to buy more amps since the fat wire is already installed :D
Presumably, the distributio0n block is over four feet from the battery. In that case you want 4 AWG to the block, then you can use smaller to the amps according to the chart. I would check the pricing, if the amps are close to the distro block, it's probably just as inexpensive to go 4 ga all the way.
Add up you fuse sizes and check the "Power & Ground Cable Specs" chart. You can probably get by with double 8 AWG to the big amp and a single 8 AWG to the smaller one, without the distro block. The drawback of too small is voltage drop, which results it amp output dropping at high volume peaks. I also have a feeling, which is just that, a feeling, that skinny wires can cause or contribute to noise problems.
Remember, Gauge is diameter and area of a circle is not linear to the diameter. In other words, two 8's do not equal one 4. Four 8's would be closer to a 4; two 8's are probably closer to 6 AWG.
Try to get all the grounds you can going to one place, and make it very clean and tight, no paint. Paint over it if you are worried about rust.
The pro's on here trump my answer. I'm a hack. Just an old hack that's been at it a long time :D
Build a man a fire, he keeps warm for a day. Set a man on fire he stays warm for life!

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