best ground spot for amp

[Guest]

where in the body of a subie wagon to get a great ground system for powering amp?

[Koom]

Anwhere near the amp that you can sand the paint down to bare metal and get a reasonable sized bolt through to fasten it and get a good clean connection to the metal. Or, run a wire all the way back to the negative terminal on your battery.

Mine usually use one of the captive nuts behind the rear seat or in the boot.

[funkytown]

 Koom said:

Anwhere near the amp that you can sand the paint down to bare metal and get a reasonable sized bolt through to fasten it and get a good clean connection to the metal. Or, run a wire all the way back to the negative terminal on your battery.

Mine usually use one of the captive nuts behind the rear seat or in the boot.

i do mine up onto the top nut on the rear stut tower top hat(but its easier in the wagon)

[dubbedup]

is there a jack holder in the wagons, i use the 12mm bolt holding this bracket down.

[wrx_lou]

I've always used either a seat mount bolt or the bolt where the seatbelt clip bolts too.

It is best to have the shortest possible ground so I definately wouldnt take a cable back to the battery. You can also get interference if you do it that way too.

[Guest]

might give that rear strut on top ay. Cheers guys. I let u all knw how i go.

[Scoobydoo]

Depends where your amp is mounted, and how big a lug you are using. An 8ga lug isn't very big and won't fit through most bolts. If your amp can take 0ga, use that and you can mount it pretty much anywhere. I have used a number of places all with success. Rear amps used the rear seat anchorages (fitted between the anchorage and the body, with the paint sanded to bare metal). Front amps (under seats) tend to use 4ga, so I use the screws that hold in the relays under the carpet on the sides, or the seat belt anchorages (again sanded back to bare metal).

Running an earth cable back to the battery isn't required, unless you want to be certain you are getting the least possible voltage drop. I've only ever done it when running 5000W (and sometimes more) worth of amps because I was entering competitions. I don't bother with it now I just have a daily driver system.

[Guest]

 Koom said:

Or, run a wire all the way back to the negative terminal on your battery.

i did that it my jeep. worked fine. bit unnecessary, but hey

[Guest]

That rear strut worked really well cheers guys. now I can vibrate again

[aim]

 wrx_lou said:

It is best to have the shortest possible ground so I definately wouldnt take a cable back to the battery. You can also get interference if you do it that way too.

What? Source?

copper cable > steel chassis. Running a cable to the battery, how would you get interference this way? All a 'ground' is, is a common return path for electric current... I fail to see how a cable will introduce an interference that a chassis would not?

[wrx_lou]

The setups I've come across wired that way have had bad alternator whine. You could posibly put that down to the length of the cable as the amps were in the boot. It is actualy recomended that your ground cable be no more than 3 feet.

[aim]

I'd be interested in the physics, do you know why?

[wrx_lou]

Probably best to google as anything I say from here in would be secondhand info anyway. I just follow instructions lol.

[D-Style]

 aim']

I'd be interested in the physics, do you know why?

Cause the flow of free electrons via a conductive matter flows from Negtive to Positive.......

If you really want check whats better do a few things: check the voltage drop between using the chassic or running a cable.

[quote name='wrx_lou said:

It is best to have the shortest possible ground so I definately wouldnt take a cable back to the battery. You can also get interference if you do it that way too.

/quote]

What? Source?

copper cable > steel chassis. Running a cable to the battery, how would you get interference this way? All a 'ground' is, is a common return path for electric current... I fail to see how a cable will introduce an interference that a chassis would not?

If you really think about it, the chassic would have a bigger cross section that than any cable you would run in the car.

Also the correct tream is "0v" not ground.

[Joker]

-ve

[wrx_lou]

Thanks for that D-style.

[aim]

 D-Style']

I'd be interested in the physics, do you know why?

Cause the flow of free electrons via a conductive matter flows from Negtive to Positive.......

If you really want check whats better do a few things: check the voltage drop between using the chassic or running a cable.

That's not why you get more interference from a cable than a chassis... that's just a simple explanation for current.

[quote name='D-Style said:

If you really think about it, the chassic would have a bigger cross section that than any cable you would run in the car.

Also the correct tream is "0v" not ground.

Ok an 'earth' or '0v' works like this (and for your information, ground is a perfectly legit term for an electrical commons in any electrical engineering application). The body of a solid contains electrons, if the body is large enough the link between positive and negative virtually need not exist. As long as across the terminals (solid bodies) there is a voltage difference. The 'earth' is a means of completing the circuit for the electrons to continue moving through components (Although they actually don't, they barely even move - but that's quantum and don't need to worry about that). With a cable I would have thought because of the minimal change in resistance amps and volts will remain constant (largely amp whine/hum is caused by a bad earth ie, voltage differences) as in this case the 'largest' (and also most directly related to supply voltage) absorber of electrons is the negative battery terminal, so it makes sense to wire it so.

I may not have worded that brilliantly - however I'm in a rush, I also concede I may have missed something and am wrong, but I'm looking for an explanation why.

[Swindog]

 wrx_lou said:

I've always used either a seat mount bolt or the bolt where the seatbelt clip bolts too.

It is best to have the shortest possible ground so I definately wouldnt take a cable back to the battery. You can also get interference if you do it that way too.

sAME!

Mines under my seat so has a cable length of about 70mm fixed to the seat bolt squished under the rail.

AIm - so what your saying is because your power is from the positiveon the battery the best place to earth is the negative on the battery because opposite attract like chalk and cheese, thelma and louise and poos and wees? lol

[Joker]

the longer the lead the higher the chance of interference from outside sources... simple enuff? like not running power and signal lines together - a long lead will run next to something eventually... be it moving (motor/parts) or electrical (ecu/and motor again)

[aim]

ooooh inductance!

[Koom]

 JoKer said:

the longer the lead the higher the chance of interference from outside sources... simple enuff? like not running power and signal lines together - a long lead will run next to something eventually... be it moving (motor/parts) or electrical (ecu/and motor again)

I think whats he's getting at is why is using the chassis better for no interference than a large earth cable?

Cause the explainations above make it sound like the chassis somehow magically doesn't pick up interference (yet it is located next to every cable in the car) but a separate earth cable would.

I use the chassis cause its easier. Did the same with mounting my battery in the boot for grounding the starter.

[aim]

 Swindog said:

sAME!

Mines under my seat so has a cable length of about 70mm fixed to the seat bolt squished under the rail.

AIm - so what your saying is because your power is from the positiveon the battery the best place to earth is the negative on the battery because opposite attract like chalk and cheese, thelma and louise and poos and wees? lol

No, in this case it's the only way. The only discussion is to whether we include the chassis or not in the loop.

[Swindog]

I wouldnt think it would matter too much on a 12v system or if you had a cap.