What's wrong with my Amp?

**joseph5458** · 07-23-2007, 01:23 AM

Hi guys, I got a few questions about an amplifier I recently installed in my car, I hope someone can help me.
so, I got a Pioneer GM-6300F amplfier a few days ago and had it installed yesterday but I didn't get the results I was expecting (Amp specifications here: http://www.newegg.com/Product/Produc...eer-_-82117108).
The amp has 4 channels and I have 4 speakers hooked up to it. The problem I'm having is that the front speakers (6.5 inches) sound better than the rear ones (10.5 Inches). Before I installed the amp the rear speakers sounded really good, but now they sound weak, as if the were not getting enough power. Now, I have a few theories of what the problem could be:

1. I ran both the ground and power cable directly from the battery (Maybe I should've grounded the amp to the body?). The power cable is 8 gauge and the ground cable is supposedly 8 gauge too (acording to writing on the cable) but it's actually a lot thinner. Could that be the problem?

2. I used cheap 18 gauge wire to hook up the rear speakers to the amp (it came with an amp installation kit I got from ebay for $20) Is 18 gauge too thin? Could that be causing problems too?

I know I should've got better quality cables but this is the first time I install an amp and didn't think the power and ground cables would make any difference. Thanks in advance for all your help.

**durwood** · 07-23-2007, 06:52 AM

Just in case you didn't notice but this site is dedicated to installing car computers. You might get better/quicker responses from any of these sites:

Have Car Audio Specific Questions?

Also, I deleted your duplicate post. You were under moderation since you added a link in your post and you are new here.

However, your ground cable SHOULD be the same thickness as your power wire so it's less strain on your amp. When you say your rear speakers are 10.5" are they subwoofers? How many do you have hooked up? Have you turned on the low pass filter if they are subs? Have you adjusted the gains properly? Those are some things to think about.

**Dennis5587** · 07-23-2007, 09:31 AM

...and yes, you should ground to the body, not the battery.

**boomintrac** · 07-25-2007, 01:45 PM

Originally Posted by Dennis5587

...and yes, you should ground to the body, not the battery.

Whats wrong with grounding at the battery?

Aron

**joseph5458** · 07-25-2007, 04:23 PM

Originally Posted by boomintrac

Whats wrong with grounding at the battery?

Aron

I was wondering the same thing. I think it's better to groud at the battery because that way you won't have any interference for sure.

**boomintrac** · 07-26-2007, 02:58 PM

I was just curious to hear his answer. I grounded at the battery because it is where I measured the lease resistance.
Aron

**pancit175** · 07-28-2007, 09:41 PM

Originally Posted by boomintrac

Whats wrong with grounding at the battery?

Aron

The only thing I would comment about that is I was originally told when I started out is that you want the ground cable to be as short as possible. I'm only talking about an install without the addition of a 2nd battery in the cabin or trunk. Although it may seem ideal to run straight to the battery's ground for efficency and less resistance, But the longer the cable is the more potential for resistance however small. Obviously to some degree, this does depend on the gauge of the wire and the quality of the wires.

Total resistance in wire=
wire length / (material conductivity coefficient x wire cross-section area)

**kostyanj** · 07-28-2007, 09:50 PM

Grounding to the body is much better than running a ground wire back to the battery. I still don't understand what you mean by 10.5" speakers in the rear. You never answered if they were woofers. You should run at least 4 awg for power and ground. As for 18awg for speakers that should be fine. But the quality of the amp/cable could be causing problems.

**Boombox** · 07-28-2007, 10:52 PM

So I was reading this thread and no one realy hit the nail on the head as to why you should ground to the body instead of running all the way back to the battery.
The way audio electronics are design they internally use a reference ground to remove un-wanted noise from the amplifcation stage. Also If you think about it, using the body ground is like using 0 gauge wire. Now if the rear speakers input channels are the last in the chain to recieve the signal chances are due to the length of the ground wire most of the signal would be suck up by the front channel inputs.

I'm sure you've already checked this but just in case. Make sure your head unit isn't faded at all, you're using the correct inputs on the amp and the crossover/gains are set correctly.

Good luck!

**PugFunk** · 08-02-2007, 09:16 PM

You ground to the car body and not the battery because you use the shortest possible length of wire for grounding as possible... You COULD run it back to the battery but there is no point and there would be more resistence in the cable. Due to friction of electrons etc.

You are better to ground to the body and then add in an extra ground strap from the (-) battery to the chasis under your bonnet... Dont forget that extra ground loop. Cars these days are not designed to return that much power to the (-) battery. An extra ground cable in the engine bay is essential.

The power being grounded to the chasis will find the shortest possible way back to the battery anyway.. It will also provide less friction because it has a greater surface area for the power to flow through. It can return using every bit of metal on the car rather than just the wires through a thin cable. Its all to do with resistance.

As for your sub issue. Check the power output using a multimeter.

Maybe its the sensitivity of your speakers. Some speakers run better off a deck if they have a higher sensitivity value. Your sub may also give differnt outputs on the front and back channels. It maybe designed to be bridged on one to provide more power to a sub and not bridged on the other.

Alpine amps provide differnt bridging values between 1 and 2 / 3 and 4. As i have mentioned because it is designed for a sub and 2 speaker set up.

Dont be cheap when it comes to wire...