power wire sizes

thanks for all the replies.  and thanks for the advice about grounding it at the battery. i went to double check and i found i only had 8 gauge wires.  guess i gotta rewire it.

from your experiences, is a cap needed with this kind of power? 1 farad cap? i think i will try it without one first to see if i really need it. thanks again for all the help.

Here are some more replies to ya'all.

(1) No it is not overkill in most cases to ground an amplifier directly to the battery. Just beacuse something is the assumed proper method does not mean it is the one and only way or necessarily even the proper way. The method I use and many other educated and informed installer and manufacturers use is to ground to the battery. But why? As someone earlier pointed out so keanly about how  much resistance is on a 16 gauge wire at 15' (which I'll talk about next), it plays on the topic of resistance on a ground lead.

Any qualified person with the knowledge of how to run a meter, a sound knowledge in math and a desire for audio may know what I'm about to say, for some of you maybe you will see this for the first time. What this equates to is you going into subway, eating a foot long sub and then having your crack sewn shut, get the point!

Electricity is like an algebra equation, what you do to one side you must do to the other. Why do you think a battery has a poitive and a negative post on it. Everyone assumes that you only must upgrade the ground wire to the chassis of the vehicle, yet very few of you take the time to measure the chassis resistance. Unhook the ground wire from your amp, take your meter and set it to resistance, take one lead and put it on the negative terminal of the battery, take the other lead and put it to the end of the ground wire that had been connected to the amp, what you get is a resistance in ohms. A reading avove .5 ohm and bad things can and usually will start to happen to your amplifier. Ever blown up your customers amplifiers and not known why? I guess the people who fix these amps when we send them in do, because it is them that after 1 customer blew his Rockford power 1000, 3 times that the problem was isolated, corrected and no problems again in 4 years. What was his resistance? 867 ohms in a 1998 chevy cavalier. In my experience in 16 years of installing and now 8 years as a store owner, I had never heard of this problem until then. It is now common procedure for my installers to ground directly to the battery. In my experience GM vehicles are the worst offenders, followed by Ford.

What problems happen?

Forget watts, you have an amplifier, not a wattlifier. In order to make power you must get power. What goes in must come out. Current flows from negative to positive, here the problem has started for most people already. With an improper ground at the amplifier, the amplifier (like your crack) cannot get rid of the negative current, this results in a builup of excessive heat in the amp, poor sound quality, a greatly reduced lifespan of the amp, trips to the service shop, whatever. Now it is true that these problems may not exist for everyone, some peoples systems play just fine, but if any of you have had a failure of your amplifier and did not know why, check your resistance on the ground lead. Genreally speaking the more intense the system, the more intense the wiring. Maybe this has shown even 1 person a small difference, maybe not. We all have our own opinions and our own experiences, just wanted to help stop a bad experience from ever happening to you. You work hard for your $, so do I. FYI the shop across the street and the big box across the street do not do this, why, because they are more interested in getting the custoer out the door and getting the next one in, this is somethkng that a specialty shop does not do.

A cap is a great idea for any amplifier system, it is designed to charge and discharge much quicker (hence the name lightning cap) than your battery can, it is closer to the amp and provides an instant burst of current for the amp when it need it. Ask pretty much anyone about dimming lights on the dash etc. and they will all say get a cap and even get a bigger alternator.

Now for the reply on the home speaker topic, go into a local stereo shop and hook it up yourself, you just might hear something. Like alot of people say, put the spec up to your ear and tell me how it sounds. I was not talking about resistane on the speaker wire, I was talking about the current carrying capacity of the wire. Here is a scenario for you to relate to. You have a barrel of water and a 2 identical pumps, each pump (the amplifier) has a hose attached to it. Your install just short circuited and your ride is on fire, do you take hose #1 (the garden hose) or hose#2 (the fire hose). Get the drift!

This is not rocket science or theory, it is something that is tried and true. What you do with this information is up to you.

And what prevents current from flowing?  Resistance.  What is preventing the water from flowing through the garden hose?  Resistance.  What I was pointing out is that there is almost no resistance.  Your above analogy is not a fair example of the wire resistance.  A better analogy of the situation would be that you have two fire hoses that one, the 16 awg wire, supplies a drop less water per minute than the other one (14 awg or larger).  Now do you really think that drop is going to make a noticable difference in putting out that fire? 

Physics still do apply.  Why you can use a smaller wire is because the voltage is much higher on the output of an amplifier.  The power wires are limited to 12  volts, so a large amount of current must flow to keep the input power the same.  But the output of the amplifier has a higher voltage, this means you can use smaller wire since the current is much smaller.  Or do you run 4 awg wire to your subwoofer? ;)

As an example, this is why they are switching to the new 42 volt electrical systems in vehicles.  They can run much smaller wires for everything, and still have enough power for the electronics.

I hope you understand that I am not trying to start a pissing contest here.  I was just trying to explain why you don' t need large awg wire for your speaker wire.  But I do have a lot of respect for you in how you present yourself.  It seems like on every other forum, if someone disagrees with you, they start flaming wars.  Thanks for keeping this friendly.

Unfortunately just before the last stereo competition I went to, our shop just ran out of 16 awg wire.  So I used 18 awg wire instead.  This was done with the CEO of Adire Audio present, who happens to be the engineer who designed the subwoofer, and I can assure you knows much more about audio and electronics than both of us combined.  If you don't believe me, do a search on his name at any car audio forum, and I'm sure you will see what I mean.  The amplifier I use is an Arc 1500dr which puts out between 1,000 to 1,200 watts.  I was able to pull a 142.3 dB with it in a .36 cubic foot sealed enclosure.  Plus the wire never got even warm to the touch.  I still haven't swapped out the wires yet, and they never get warm.  And that's with a kilowatt of power.

No offense please, but I find all sorts of questionable statements in your post, beyond the obvious of hearing these "audible and repeatable" differences in wire..

Fundamentally, this being a "sales ploy" that you "were taught" seems infeasible at worst, and fundamentally pointless [as a speaker sales technique] at best.

Sure, ohms law... V = I x R.

Except your claim is that the bass response of the speakers being auditioned changed, not the overall volume levels - which would fundamentally scale up and down across the entire frequency range, should simple DC resistance change.

Perhaps most fundamentally, the wire gauges you are comparing are simply too small, particularly with the small amount of power flowing through the wire, particuarly in your audition scenario.

The difference in capacity between 12 and 16 gauge isn't very large to begin with, the current carrying capacities of the two wires is likewise not dramatically different.

So it's not likely that you would have stressed the 16 gauge... possibly not even 22 gauge or smaller, depending on how loud you were running.

With reference to your comment of "running a ground wire from the amps directly to the battery", this is actually wholly a bad idea, for many reasons.

Primarily, your car chassis IS tied to the negative terminal of your battery, via a very short length of power wire - and the total amount of metal comprising your car's chassis would make for one MONSTER gauge wire.

Now, I could see a myth like what you state being concluded by a misunderstanding installer who failed to secure the amp's ground to the chassis via a solid (and bare) metal-on-metal connection, or maybe even who was exceeding the current flow capabilities of the stock battery ground or alternator power wire limitations.

Finally, it's not the strand count at all that dictates the current carrying capabilities of the wire.  The only thing a higher strand count does is make installation easier, because it will be inherently more flexible.

Hopefully that clarifies a few tiny details for everyone... 

Oh, and hi, btw... nice forum.

The actual chassis as a return path for current isn't a bottleneck.

Hence, anything wired between the positive and negative terminals become a load on that voltage source, in the circuit itself.

Anything wired in series in that circuit contributes additively to the resistance in that circuit.

Measuring the macro, and then blaming one discrete factor as the cause is very unscientific, and your assumption is leading you to the wrong conclusion.

You clearly described a very "macro" measurement technique here:

Rather than discussing how simply unrealistic that number actually is, let's discuss the flaw in your measurement.

Inherently, if you unbolted your amp's ground wire from it's location, and unbolted your battery's ground wire from it's chassis-mount location, touched the terminals of your multimeter to the threaded holes left behind, you'd inherently measure something only nominally exceeding 0 for resistance.

One likely location for problem is the stock battery ground, which often is NOT bare metal-on-metal... rather, it's bolted to the painted chassis, and paint is an insulator.

And similarly, you could have poor connections and the like elsewhere in that macro, all-encompassing path you are measuring.

...and It simply isn't "common practice" to run ground wires back to theb attery... common practice is to ground to the chassis - in a proper manner, of course.

A circuit is more like a circular train track... which is occupied by a train with many cars, extending all the way around the train track, so that the nose of the engine was actually hitched right back into the rear of the caboose.

That's analogous to a part of a circuit representing a nearly infinite resistance.... like cutting the wire, or unplugging a fuse.

That's really basic electricity...

Again, there's really no such thing as overkill when it comes to wiring... but even if you need to stick to the smallest you can get away with (possibly financial constraints), there are charts available to let you know what proper wiring gauges are, given potential current draw and wire run lengths.

In reality, you are comparing two pieces of wire, that might have many distinct differences, only one of them being their gauge.

That's actually quite analogous to the scenario here...