Wiring Concerns

[idiot 10+ year member]

Now that I’ve chosen which electronics and components of my future system I will be getting, it’s time that I learned how to properly connect them.

First, the amps.

I have two amplifiers that draw 50 amps a piece. Both will be placed beneath the driver’s seat, which is 5 to 10 feet from the battery (depending on the twists and turns of the wire). I intend to run one power and one ground wire through the firewall, to a pair of distribution blocks. For a 100 amp total draw that runs less than 10 feet, I assume that a 4 gauge wire will be sufficient.

Power wire

Inline Fuse (for power wire)

Inline Fuse Holder (for power wire)

Ground Wire

The power wire will connect to a fused distribution block, which will split the signal to two 8 gauge wires (two 50 amp loads). The blocks will be under the same seats as the amps, so the split signals will travel less than a foot.

Fused Power Distribution Block

The ground wire will connect to an unfused distribution block, also splitting the 4 gauge ground signal into two 8 gauge wires to connect with each amp. Again, the split signal will only travel a few inches.

Ground Distribution Block

Now, this part of the design rests on a few assumptions that I’m not sure are correct.

1) The ground should be connected directly to the negative terminal on the battery, which would reduce the possibility of alternator whine caused by bad grounding locations. Since I don’t think I want to ground inside the cabin, I would end up running the ground wire into the engine bay anyway, so I might as well ground to the battery.

2) The ground and power wires can be run side-by-side for as long as I want without any adverse effects.

Now that the hard stuff is out of the way, let’s briefly move to the head unit and speakers.

I will be using a head unit with only two pre-outs (front and rear). As such, I will need two RCA cables. I’m not sure what I should look for in a cable, but this seemed a decent price. I know that some people spend considerably more, yet others swear that there is no discernable difference in the $15 RCA’s and the $50 ones. I’d appreciate some input. But for now, these look good.

RCA Cable

Now I’m not quite sure which kind of speaker wire I should be getting (either the kind with positive and negative twisted around each other, or the kind where the positive and negative run parallel). I’ve heard that the twisted wire helps to reduce the chance of picking up noise… or something? Could someone explain this to me? I was looking 14 gauge wire (they’ll be pushing more than 180 watts… I’m not sure if 16 gauge would work), but I’m not sure which kind to get.

Also, what gauge would safely push 350-400W? I need to pick a size to fit my sub.

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[helotaxi 5,000+ posts]

3) Your ground should be as short as possible, so grounding to the battery may not be the best idea.

With a truck, the sheetmetal and the frame make a pretty good ground path. With the amp under the seat, just ground to the seat bolt and you will be fine. If you were working with a unibody or were using high-powered amps you might want to run the ground back to the battery, but it usually isn't needed.

Noise is caused by a bad ground in only so much that the different components in the system, HU and amps usually, have a different ground potential. If the ground on your amp is not solid and/or the ground path back to the battery is of a higher resistance than the ground path through the RCA cables to the HU and through the ground wire on the HU, then the amp will partially ground through that path and that will cause noise. Same can happen if your HU is not grounded as well as your amps.

 

[idiot 10+ year member]

1) Buy the 4 gauge dual amplifier kit from Walmart ($25). It has everything you need except the speaker wire and another distribution block and is of pretty good quality.

Interesting. I’ll consider it. I’d just have to get over my anti-Wal-Mart prejudice. //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

2) 16 gauge speaker wire for the speakers and 14 gauge speaker wire for the subs should be adequate. Don't worry too much about buying expensive wire, just buy cheap stuff.

16 gauge will be able to carry 180W for ~20 feet? I was under the impression that a larger wire would be needed for that. And is there any merit to the suggestion that the twisted speaker cable rejects noise much better than parallel wire? Because on eBay, the price for twisted Stinger is not much more than comparable length quality Home Depot wire.

With a truck, the sheetmetal and the frame make a pretty good ground path. With the amp under the seat, just ground to the seat bolt and you will be fine. If you were working with a unibody or were using high-powered amps you might want to run the ground back to the battery, but it usually isn't needed.
Noise is caused by a bad ground in only so much that the different components in the system, HU and amps usually, have a different ground potential. If the ground on your amp is not solid and/or the ground path back to the battery is of a higher resistance than the ground path through the RCA cables to the HU and through the ground wire on the HU, then the amp will partially ground through that path and that will cause noise. Same can happen if your HU is not grounded as well as your amps.

I actually drive a Toyota Matrix; it’s a small wagon, not a truck. I should have mentioned that earlier. And I’m fairly certain that it is of unibody construction. While grounding to the seat bolt would be significantly easier (and cheaper), I was under the impression that this would not be the best location for contact.

On the subject of things I should’ve mentioned earlier, here’s my system:

HU: Denford RFX8250

Components: Focal 165K2P

Component Amp: Zapco I-450

Sub: ID8 V.3

Sub Amp: Zapco I-2100

 

[idiot 10+ year member]

I got the 4-channel amp for my components because the I-450 pushes 2 x 180W @ 4 Ohms, while the I-2100 only pushes 2 x 100W @ 4 Ohms. So the specifications were the deciding factor, in this case. Granted, the Focals are rated at 100W continuous (though they supposedly perform quite nicely with much higher wattage), but since both amps were the same price, I saw no reason to get the lower-power one. I’ll just be sure to use the gain knob responsibly.

Also, I doubt that I’ll be running the amp’s full power through the wires very often, but I’d rather not have the current limited (and my car endangered) by the size of the cabling.