Testing Ground Points

Hi

Im new to car audio, and have run into problems with my setup. My problem is that my newley installed sub and amp were very weak with the bass (not so loud bass and some distortion) compaired to when it was installed in the previous owners car. I moved the ground point and the bass increased to a very good level with no distortion. It then decreased after a while to its initial level and have been unable to figure out why. Is this the sign of yet another bad Ground?

The main question though is how do i test the ground? I have a digital multimeter and know basic electronics...

Thanks in advance!

Your ground is very important to the sound system in your car. First, make sure that you have at least the same size wire for ground and as power, if not bigger. Second, make it short as posable. Third, make sure its a very clean metal spot you ground it to. You can test a ground by attaching one side of the metter to the ground and then the other side to the ground on the battery, you should get 1 to 5 ohms max resitance. You may also have what is called a ground loop which can cause problems and add noise to the system. To prevent ground loops make sure that the deck is ground to a good ground and all your amps are grounded together. Also make sure the rca's are not grounded. Try that and get back to me, if it dosent work i have a few  other ideas for ya.

Ok, i thought this was how you tested the ground, but wanted to make sure before i do. I will try your suggestions tomorrow, its 2:30am here. As regarding to the wiring, im using a Amp wiring kit, consisting of 5m 4awg power cable, 0.5m 4awg earth cable, 5m remote wire, 5m (shielded i think) rca cable and 3m speaker cable.

Thanks for the advice and i will get back to you tomorrow with my findings.

Edit: i also would like you to know that the power cable is run down the left side of the car and the rcas are run down the opposite side, as advised by a friend.

Right, i regrounded my amp and the sound came alive! i tested this new ground and found that the multimeter wouldnt register.... so i assume there was no resistance (or very little). However i am getting added noise now when the car is running, in both of my amplifiers. I've tried earthing the headunit to the same ground as the sub amp but it didnt make a difference. I will try moving the ground on my 6x9 amp to the same as the sub amp tomorrow, but i got a feeling the noise is a ground loop from the RCA's? how do i check the RCA's?

What do you advise me to do to solve this?

Getting this back up top, i really need help, its driving me nutty!

I have a 600watt Amp running the Sub, and a 300watt Amp running the 6x9s. Both amps are grounded to the same point now, but still i get the noise. I've even tried earthing everyting direct to the battery but i still got the noise. I have now noticed however that i am getting the noise direct from the head units hi output wires too, but seemingly only from the back channels (which i connected my 6x9's to temporarly to get rid of the noise so that i can listen to it when im moving!) but it is nowere near as loud as when its amped. I've tried a ground loop isolator inline with the RCA leads, no cure... i even got a noise supressor for the head unit (connects to the +ive wire) and still no change in the noise level.

I do have the feeling that its the alternator, i got a brand new battery about 3 weeks ago cos of the occasional dead battery but i assumed it was due to me using the sub without the engine running. Do you rekon i need to get the alternator replaced/fixed?

Thanks in advance!

I've noticed now that everything electrical is interfearing now.... the heator fan, indecators, and when lights and stuff are switched on i can hear like a click or a pop... so its not only alternator noise...

Any sugesstions?

Try upgrading your ground wire from your battery to your chasis ground.  The thicker the better.  Sounds like you have more than one ground loop...

O and the proper way to check for a good ground is to put the negative cable of your DMM on the negative of the battery cable and the positive to the spot where you want to ground.  Make sure you remove all paint and primer on the spot and test.  You should not read any voltage...If you get any voltage locate another spot until you get 0volts......

Right, well im going to tell you about how its set up right now, and the problems im facing. I know its not set up the proper way but im trying to eliminate the noises by different wiring...

I have 4awg wire for the positive going directly to the positive terminal, then 8awg to each amp from a power distributer. Exactly the same for the ground wires, i know its not the proper way but i tryed a proper earthing technique but it didnt help. These wires are run down the left hand side of the car. It powers a 300w amp for the 6x9s and a 600w amp for my sub. The noise is coming from both amps, and even from the hi-outputs of the head unit itself, but seemingly only from the rear channels, but not as loud as when amped. But when the 6x9s are direct to the head unit, all i hear is the alternator whine, but when amped, i hear everything electrical interfearing. My RCA's are run down the right hand side of the car. I've tried wiring the head unit directly to the battery too, but i still hear the noise. I've tried a noise supressor on the rca leads (plugs in line with the rcas) but it seemed to cut most of the sound, sorta like cutting all the mono sounds and only letting stereo through, but the noise was still there. I've also tried a supressor that is wired inline with the positive side of the head units power wires, but it did absolutely nothing.

Any sugestions? is this induced noise? should i try moving the rcas? I'll only try it if you believe this is the problem as its routed in the wells and is awquard and time consuming to move them....

Thanks in advance!

You mentioned before you might be using a shielded RCA cable.  If this is the case, make sure the shield is only connected to ground at the headunit end and the end at the amp is left disconnected.  Instead of removing the RCA's you can just unplug them and run another set through the car temporarily for testing.