long ground to battery

[kkmike]

I had a new amp installed yesterday (JL 450/4) - my 2nd amp, and since the 1st amp (JL 500/1) was running off 8 gauge wire, they wanted to run 4 gauge. So now I have 2 runs of 4 gauge, 1 to each amp; but he also ran 2 runs of ground back to the battery. I have read numerous times that ground should be short and to the chassis. And it's a long run since this is a Suburban. He said JL recommends grounding these amps directly back to the battery and so that is what he did. Well now I have alternator whine that fluctuates with the speed of the engine; worse the higher the gains are set. The RCA's & speaker wire don't run along with the power wires, so I'm hopeing I can rule that out (they do cross where they all meet up at the amps, but that shouldn't be a problem?)

I don't want to go back and leave the car there again, it's a pain - I can do it myself - there is a seat bolt right there. So I have 2 questions; Is the ground most likely the problem, best place to start? And if so, should I disconnect the long ground and replace it with the short, or just add the short and leave the long ones too?

Thanks,

Mike

Click to read more...

 

[xjmadness 10+ year member]

JL reccomends running ground back to battery? wtf. That sounds a bit iffy. Have them ground the wires to the chasis. Make it as SHORT as possible

 

[forbidden 10+ year member]

JL Audio is correct, one should understand the reasoning as to why instead of following the lemming over the cliff. Reground the cd player to a different spot. Are you using an eq or other processor?

 

[buchel 10+ year member]

I like lemmings, they're cute...

~ Kyle ~

 

[kkmike]

JL Audio is correct, one should understand the reasoning as to why instead of following the lemming over the cliff. Reground the cd player to a different spot. Are you using an eq or other processor?

JL contradicts themselves then. I re-read the manual and the manual states a short ground to the chassis. What is the reasoning then behind the long ground?

I'll check the HU ground then too. No eq or other processor, just an Alpine 9813, 2 amps, 4 speakers, 1 sub.

 

[DBfan187 5,000+ posts]

This might help out?

http://www.caraudio.com/vb/showthread.php?t=48345&highlight=ground

 

[forbidden 10+ year member]

Not really, all it shows is differing opinions. Fact is electricity is an algebra equation, what you do to one side you must do to the other. Helotaxi is bang on with his recommendations, more people need to be made aware or the proper way to do things vs. the assumed proper way of doing things. He asked if anyone had checked the resistance on the ground return, many installers do not infact do this when they should be, especially with the plethora of crappy power supplies put into amplifiers these days. When a person is faced with a high resistance on a ground return that cannot be rectified with upgraded grounds etc (ie the big 3), and it has been proven fact that the resistance is higher than .5 ohm, it is necessary for the amp to be grounded to the battery. This has nothing to do with the amount of metal used in the ground plain, the type of metal used in the ground plain or the price of rice in china, it has to do with the resistance in the ground plain, which helotaxi rightfully popinted out, but some people do not understand.

Todays vehicles are not 16 gauge solid steel , bolted to a chassis and is heavier than any vehicle today. Today's vehicles are a combination of thin sheet metal full of impurities (scratch the paint and see coca-cola underneath), glued together unibody panels and crappy tack welds, coupled with small ground wires from battery to chassis.

If one does not understand resistance on a ground return they had better find out what it is, how it affects an amplifier and it's outpout and how to correct it. Even I had no idea about this until 5 years ago after a long string of Rockford amp power supply failures. Rockford successfully duplicated the problem at their facility and recommended to me on how to solve the problem. Imagine my surpise when I checked exactly what they said to and correct the problem, I have not seen this customer again in almost 5 years now. I also double checked alot more of my previous installs for the same problem and now check every install, it's called being thorough for the paying customer.

 

[kkmike]

Here's a reply I got from JL when I asked why the owners manual reccommended short ground, but they told the installer otherwise:

"Mike,

Thank you for your interest in JL Audio. In the owners manual, you are going to find a recommendation to have the ground as short as possible. This can be done with most vehicle and most audio amplifiers. You can run a ground wire back to the battery. This can be better then grounding to the chassis of a vehicle. As long as the ground wire is as large as the positive wire, there is no problem.

We have done some testing on all different vehicles. This test was to measure the resistance of frames and uni-body constructed vehicles. The best are the vehicles that have a true frame rail, like your Suburban. You want the ground wire from the amps to be mounted to the frame. You also want to upgrade the factory ground return wire. This runs from the negative side of the battery to the frame. Now the best results only equaled the same resistance as a 4awg wire. Uni-bodies are like an 8awg.

This installer made sure that the ground return of the amplifiers do have the least amount of resistance. This preventing any type of voltage choke.

There is no problem doing this. As long as it is done correct. In this case, I am assuming it was."

 

[paikiah 5,000+ posts]

did someone mention "ground"? This is my "ground" job. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

(FYI: ground is red, positive is blue)

Do this in your engine compartment, then have a short thick ground at the back of your car's chassis and you should be good to go. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

I run a 135A alt, so a 4 gauge is PLENTY.

I have 5 grouding points here.

1. Engine block

2. Throttle body

3. Alt

4. Transmission (not shown in the pic)

5. right fender (the strut also acts as a ground cable)

For the positive, so far I only linked it to the alt, and since I got excess cable remaining, I was thinking about running a 4gauge to the starter (if I can bloody find it)