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  • What's wrong with my Amp?

    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.

  • #2
    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:

    http://www.mp3car.com/vbulletin/car-...questions.html

    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.
    System always under construction


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    • #3
      ...and yes, you should ground to the body, not the battery.

      2006 Mazda 3
      Behringer DCX-2496
      JL300/4 Focal 6W4311B Focal TN52
      JL500/1 JL10w6v2

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      • #4
        Originally posted by Dennis5587 View Post
        ...and yes, you should ground to the body, not the battery.
        Whats wrong with grounding at the battery?
        Aron
        New Ipad
        Zapco DSP-6SL
        Zapco Reference 360.4: H-Audio Soul, x2 right side
        Zapco Reference 360.4: H-Audio Soul, x2 left side
        Zapco Reference 500.1: JL Audio 10W3V3 Stealth box

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        • #5
          Originally posted by boomintrac View Post
          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.

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          • #6
            I was just curious to hear his answer. I grounded at the battery because it is where I measured the lease resistance.
            Aron
            New Ipad
            Zapco DSP-6SL
            Zapco Reference 360.4: H-Audio Soul, x2 right side
            Zapco Reference 360.4: H-Audio Soul, x2 left side
            Zapco Reference 500.1: JL Audio 10W3V3 Stealth box

            Comment


            • #7
              Originally posted by boomintrac View Post
              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)
              "In the beginners mind there are many possibilities, but in the experts mind there are few."- Shunryu Suzuki
              "Do it right or don't do it at all"

              PROGRESS:
              [-------90%-] (New Car=New Build)

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              • #8
                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.
                www.computer-forums.net

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                • #9
                  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!
                  Automotive diagnostics? I/O controls? ppfffff...... No problem!

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                  • #10
                    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...

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                    • #11
                      Just a few additions to this as there seems to be quite a bit of mis-information on this subject with no real answers other than, "well, it says to do this in this forum, etc...."

                      Firstly, running a ground wire back to the battery directly is actually the BEST way to do it as far as noise is concerned. However, i suspect its frowned upon because a) you have another wire to physically run, and you also have to worry about any IR drop in the wire. Connecting to the chassis is more of a "practical" issue, then optimal arrangement.

                      Why?

                      Firstly, without getting into theory here, noise pick-up in an electrical circuit is directly proportional to the amount of loop area between your outgoing (i.e. +12v) and return (gnd) wires. The larger the loop area formed between the two wires, the more efficient it is at picking up noise. Also, the larger the loop area, the more efficient it is as RADIATING noise as well!

                      Now why does running a separate +12V and GND wire better? Well, because you have absolute control to how the outgoing and return signals are routed. If you twist those wires tightly together, or have them right next to each other, loop area is minimized, and you know EXACTLY where that power current is flowing. Not only do you minimize noise pick-up due to the reduction of loop area, but you also have control over the isolation between those lines and other signal wires etc...

                      Now if you ground to chassis, you know where the +12V current is going, but have NO IDEA where the GND current is going. Depending on how your chassis is built and shaped, that GND current could be flowing all over the place creating huge loop areas, and also any signal wires you have or other power connections that share the chassis ground will get affected.

                      So you could carefully design your system, running power wires on the right, and signal wires on the left, and basically have your return current flowing right there on the right with your signal wires.

                      Also, running separate wires to the battery directly will reduce ground loops as you have complete control of where that current is going, as opposed to allowing it to flow on its own in the chassis where you can't control it.

                      Of course, in the end, it comes to a trade of performance vs. practicalily for the given application.


                      The power being grounded to the chasis will find the shortest possible way back to the battery anyway..
                      Which is not the best thing. True, DC will attempt to find the path of "least resistance" (whereas AC will attempt to find the path of "least impedance" which is NOT necessarily the shortest path) but that "shortest" path, could be practically anywhere depending on the design of your chassis. Say you have a +12V wire with 100A of current flowing through it and you ground through chassis. That chassis return current could be anywhere, coupling with other devices " return current" and also any signal wires that are routed in proximity with the chassis. With a separate +12V and GND wire, you control exactly where that current is flowing. But again, with 100A of current flowing, it would be more practical power-wise (IR drop) to utilize a low resistance return such as chassis. But for noise, the separate wires are optimum.

                      But don't fret. As well as a power systems engineer for Lockheed Martin (designed power systems for everything from naval radar / weapons systems to military aircraft (i.e. F-22 Raptor), to satellites, i am also one of the company's EMI/EMC consultants. And from experience, i would say even 99% of most electrical engineers don't understand EMI/EMC related issues.

                      If you want more information and to read up on the BIBLE, so to speak, on EMI/EMC, then check out the following publication:

                      "Noise Reduction Techniques in Electronic Systems"
                      Second Edition
                      By Henry W. Ott

                      His website is here which includes a lot of FAQs, etc... on grounding. He is considered the guru in this subject.
                      http://www.hottconsultants.com/

                      Dont be cheap when it comes to wire...
                      I assume you are referring to size of wire. If you are referring to that "fancy" speaker wire with internal dielectrics etc..., thats all marketing BS. For audio frequencies and a given size of wire . . . copper wire is copper wire. Don't be fooled by your local audio salesrep.
                      Eastern Voltage Research Corp.
                      http://www.easternvoltageresearch.com

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                      • #12
                        ^ Finally someone had the guts to say it.

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                        • #13
                          Originally posted by eastvolt View Post
                          Firstly, running a ground wire back to the battery directly is actually the BEST way to do it as far as noise is concerned. However, i suspect its frowned upon because a) you have another wire to physically run, and you also have to worry about any IR drop in the wire. Connecting to the chassis is more of a "practical" issue, then optimal arrangement.

                          Why?

                          Firstly, without getting into theory here, noise pick-up in an electrical circuit is directly proportional to the amount of loop area between your outgoing (i.e. +12v) and return (gnd) wires. The larger the loop area formed between the two wires, the more efficient it is at picking up noise. Also, the larger the loop area, the more efficient it is as RADIATING noise as well!

                          Now why does running a separate +12V and GND wire better? Well, because you have absolute control to how the outgoing and return signals are routed. If you twist those wires tightly together, or have them right next to each other, loop area is minimized, and you know EXACTLY where that power current is flowing. Not only do you minimize noise pick-up due to the reduction of loop area, but you also have control over the isolation between those lines and other signal wires etc...

                          Now if you ground to chassis, you know where the +12V current is going, but have NO IDEA where the GND current is going. Depending on how your chassis is built and shaped, that GND current could be flowing all over the place creating huge loop areas, and also any signal wires you have or other power connections that share the chassis ground will get affected.

                          So you could carefully design your system, running power wires on the right, and signal wires on the left, and basically have your return current flowing right there on the right with your signal wires.

                          Also, running separate wires to the battery directly will reduce ground loops as you have complete control of where that current is going, as opposed to allowing it to flow on its own in the chassis where you can't control it.

                          Of course, in the end, it comes to a trade of performance vs. practicalily for the given application.




                          Which is not the best thing. True, DC will attempt to find the path of "least resistance" (whereas AC will attempt to find the path of "least impedance" which is NOT necessarily the shortest path) but that "shortest" path, could be practically anywhere depending on the design of your chassis. Say you have a +12V wire with 100A of current flowing through it and you ground through chassis. That chassis return current could be anywhere, coupling with other devices " return current" and also any signal wires that are routed in proximity with the chassis. With a separate +12V and GND wire, you control exactly where that current is flowing. But again, with 100A of current flowing, it would be more practical power-wise (IR drop) to utilize a low resistance return such as chassis. But for noise, the separate wires are optimum.

                          But don't fret. As well as a power systems engineer for Lockheed Martin (designed power systems for everything from naval radar / weapons systems to military aircraft (i.e. F-22 Raptor), to satellites, i am also one of the company's EMI/EMC consultants. And from experience, i would say even 99% of most electrical engineers don't understand EMI/EMC related issues.

                          If you want more information and to read up on the BIBLE, so to speak, on EMI/EMC, then check out the following publication:

                          "Noise Reduction Techniques in Electronic Systems"
                          Second Edition
                          By Henry W. Ott

                          His website is here which includes a lot of FAQs, etc... on grounding. He is considered the guru in this subject.
                          http://www.hottconsultants.com/

                          Do you think automotive engineering and design departments take that in to consideration when they design the chassis and pick the chassis-ground locations? Or maybe that the ill-affects are negligable and don't need to be addressed?
                          I could imagine part of the body being designed with a bit more thickess and vectored from rear to front in a manner to 'pick up' all of those grounding points and deliver them to the neg battery cable connection.
                          I know there's cost and weight to take in to account when making these determinations (neg cable vs. chassis common), but seems like something simple like that would be a good compromise. All in all, I'm no aerospace engineer, but it seems they have deemed the effects negligable, looking at their product. Then again, they're not putting huge subwoofers and amps in their systems.
                          It's been a while...

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                          • #14
                            i completly agree with eastvolt on the voltage and grounding points.

                            as to your 10" speakers sounding worse than your 6.5", you never metioned what size wire you are using to run your front speakers. wire gauge makes a HUGE difference in sound. heres how you can test this-----at home depot, or menards, they sell wire by the foot---get two runs of a few feet of 16 gauge, and 14 gauge, and then go home and cue up one of your favorite cd's, first listen to the detail that the 18 ga. wire allows, then switch out the wire to 16 ga. to both 10"speakers and lissten to the same selection again, you should notice a difference in the overall clarity of the track---enhanced treble, clearer, more defined bass, then switch over to the 14 ga. and the clarity should increase, that is why most people recommend 12 ga. wire for larger speakers(larger wire=more electron flow=clearer details)

                            also check the settings on the amp---especially the crossover section, and make sure the gain is set correctly

                            because it is a 4channel amp i believe that your problem lies somewhere in your setup and not your amp---the amp uses a single input for power meaning that all 4 speakers have the same power supply, if it is your amp, you can test this by simply switching terminals-hook up the 6.5"s where the 10's are, etc. if the amp is really bad, than your 6.5's will be the weaker set

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                            • #15
                              Old thread but since some new discussion errupted I felt like adding to some of the newer comments.

                              "Don't go cheap on wire"

                              I think the best thing to worry about is to make sure you are really getting what you pay for. Copper is expensive now, something that wasn't an issue years ago. Many wire companies are skimping on copper and beefing up the insulation and selling it as a certain gauge of wire based on the diameter of the entire wire INCLUDING the insulation. Just beware. Reputable companies are not doing it, but cheaper knockoff companies are. Beware!

                              Regarding the discussion on running a ground wire to the battery, there is nothing wrong with doing it. If you want to make sure you have a rock solid ground, then that is the way to go. Grounding to the vehicle chassis can be fine as long as you are using solid ground points (most people fail here though). However, I have heard some discussion about newer cars not using welds as much anymore for the body, but are instead "glueing" parts of the body together. If this is true, you could run into ground problems. But until I see proof myself, I'll stick with using the cars body as my ground point, and make sure the ground is solid in the engine compartment.
                              System always under construction


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