wiring gauge to amplifier

Hi Guys,

This is my 1st  post, so here goes. I just recently upgraded my amp (Sony 600w) to a MTX thunder TC 4004 ,400w RMS.

Running rear channel bridged on one 12 '' MTX 300W RMS sub.

Exisiting power and ground wire gauge is 10 gauge. 

4 gauge wire is recommended. Question : Will I get better deeper bass by switching to the 4 gauge.

Thanks. 

dwarren, I have a question about your reply..not trying to start an argument but if what you stated is true, I don't really understand why.

Now the poster did not mention the ohms value of the sub so we don't know the actual power output .... I will assume the max. power,.which is 400w rms. for the sake of this topic. The current demand would call for greater then a 10ga, I would say to be safe at least an 8ga. for a 15 foot run..Iasca would call for at least a 4ga. which is what I would use as well.

So..by using the proper gauge most of the voltage drop that can occur though the smaller ga. wire will be eliminated. There is really not enough info given to predict what the poster is asking...to quote "Will I get better deeper bass by switching to the 4 gauge", however it is a possiblity. Well technically I don't think "deeper" is the right term..that has to do with tuned frequency..but the bass might be louder and cleaner...regardless, this is not really where I have issue.

The following statement..."Using a power wire that is too small for current draw demands will put excessive strain on electrical components" is where you lose me.

If the wire ga. is too small...the result is voltage drop..so..how can having less voltage going to the amp cause a strain on any eletrical components? I can see this putting a "strain" on the power wire and creating heat..not the best thing ,but I would tend to think the only noticible "side effect" if any would be poor or "less then optimized" amplifier performance .

To add to this..although I can't speak for everyone..common sense should dictate that if an amplifier is not getting enough voltage to the point of noticing it by ear, that it would be dealt with long before actual damage was caused by it...if it is possible. So in a nutshell I am asking if it is possible for an amp to be damaged from voltage drop causing a strain on the components....how is this possible?

Thanks

Thank you both for replying to my post. I did forget to mention that my sub is rated @ 4 ohms.

Custom Audio you do pose a very interesting question and I am interested in the outcome of your query.

I was hoping that the 4 gauge upgrade will improve the quality of the bass.

Cheers.

It causes excessive strain on the components because that extra heat in the power wire also results in the components of the power stage of your amplifier.  Basic ohms law  and power equations says that if less voltage is reaching the amplifier it will draw more current to produce the same power, (Watts=Volts*Amps) The performance of all solid state circuitry particularly (but all circuitry to some degree) is dependent upon temperature.  Just look at the tech sheet for a transistor, it has graphs of how certain characteristics of that part are affected by temperature.  More importantly the base junction or gate junction can be destroyed by heat and the part fails.  This is why amplifiers have heat sinks on them.  It helps disipate the heat of the transistors and protects them from thermal breakdown.

I hope this makes sense.  I would be happy to elaborate more if it is needed.

SoundAudio, thanks for responding..this is becoming interesting.

I undertand using ohms law...if we assume the power output will be the same regardless of voltage...and we lower the voltage in the equasion  I = P / E that it will show an increase in current.

What I can't understand is why the power does not decrease if the voltage is lower. I know the wire gets hot if it is too small because of friction..too many electrons are being called upon by the amp..they can't all fit at once during peak demands....ouch..hot wire...voltage drop as well.

Now the amplifier will draw current..as much has it needs to operate..but it requires a certain amount of voltage...if it loses V however....lets say a weak battery....current available will decrease..power will decrease..heat will decrease. realize I am not coming from an engineering standpoint...just common sense.

Now how can the amp tell the difference if the drop is from a wire that is too small...or a dying battery? It should only notice a decrease in voltage..wouldn't you think?

Have you or anyone actually experieced or seen an amp run hot ONLY because of a small wire?

I know in my experience I have seen heat problems due to running ohms loads too low...or inadequite ventilation.

Now if this is true..and I can be convinced of it, understand that I always use wire that is larger then required..overkill , and if I see a system with the wrong wire ga. come in with problems I won't touch anything until the right wire ga. is installed.

But the problems I expect from the wire being too small is voltage drop....causing the amp to shut off at peak demands and limting power..which limits output..which limits SPL..so on....but heat from too low a voltage??? I would be much quicker to believe with everything I have learned about amplifiers that too much voltage will cause a "strain" on the amps internals..not too little.

Can ya see my point? If I am wrong please help me to understand. Thanks.

I did make the assumption that the power would stay the same which is not typically the case, you normally get more output at 14 volts then 12 volts.  The amplifier will still demand more current if the voltage is lower.  The increased heat from the greater current draw reduces the robustness of the circuit, and in turn reduces its life span. 

Sorry to pick your brain..and thanks for taking the time.

So..will the type of power supply of the particular amp make a difference with this subject?

Should I conclue that lower voltage can cause more current draw (I just can't argue with ohms.law..it is a law)..which can cause more heat...In other works can we expect every system that has smaller wires to the amp to run hotter? If I share this info..which is new to me..I want to be 100% sure I can back it up. I have searched the internet for a good hour and can not find any useful info on this subject at all. Why the secrecy?

thunder-x wrote:

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Exisiting power and ground wire gauge is 10 gauge. 

4 gauge wire is recommended. Question : Will I get better deeper bass by switching to the 4 gauge.

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No.  1/0 gauge is much larger and more capable than 4 ga.  The amplifier is recommending minimum 4 ga.

(K.I.S.S.)

thunder-x wrote:

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Hi Guys,

This is my 1st  post, so here goes. I just recently upgraded my amp (Sony 600w) to a MTX thunder TC 4004 ,400w RMS.

Running rear channel bridged on one 12 '' MTX 300W RMS sub.

Exisiting power and ground wire gauge is 10 gauge. 

4 gauge wire is recommended. Question : Will I get better deeper bass by switching to the 4 gauge.

Thanks. 

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It appears you are talking about POWER and GROUND, not speaker wire.  You need to use the proper gauge wire for the current draw of your amp.  I recommend 4-AWG for both power and ground for your 400 watt amplifier if the total length from your battery to the amp is 10 feet or more.  If it's less than 10 feet, you can get away using 8 AWG.  Remove the 10 AWG wire from your car.  Be sure to fuse your power wire at the battery - if your use 4 AWG you can use up to a 150-amp fuse.  If 8 AWG, up to 100 amps.

Using the correct size power wire will not make the sub hit harder or play lower, but it will keep your vehicle from burning to the ground due to the amplifier power draw through the wire.

Custom Audio NY-

I will give you an example from Introduction to Electroacoustics and Audio Amplifier Design by W. Marshall Leach, Jr. Chapter 12, pg 261, example 28.

It is desired to design a stereo amplifier that will put out 100W of average power per channel into two 8 ohm loads.  It is estimated that the power supply voltage drops 10% at maximumpower output and that the amplifier clipping voltage is 7V lower than the power supply voltage. Calculate the required no-load power supply voltages.

Vclip = sqrt(2*Rload*Paverage) = sqrt(2*8*100) = 40V

The power supply voltages are thus given by plus and minus (40+ Vdrop)/0.9; Vdrop is the drop across the output transistors, which we will assume is 5V. So supply rails = +\- (40+5)/0.9 = +\-50V

The amplifier input will desire enough current  at the input so that the rails wil reach +\- 50V, the voltage at the input will drop but the amplifier can't easily demande more voltage like it can current.  The larger gauge input wire is used so there is less resistance in the wire when the amplifier has an increaed current demand for a large power output, which you already know.  I hope this helped you out.

DYohn answered the power wire precisely for the original question.

OK...so what we learned here is that using a wire that is a gauge or so too small..will burn up the amp..and/or burn the car down????? Did someone put a 150a fuse on a 10ga wire or did I miss something here??

Maybe if the speaker wire is too small it will slip out from under the carpet and a pet will choke on it..or..catch someones foot and they could trip and fall......hey..it's a possibility right?

Well anything is a possability......but statstics says the pet thing is unlikely. If you used a wire gauge that is too small but fused properly then you will likely keep blowing the fuse on the power wire and be replacing it constantly which really has no point.  If it is fused to high or you run it to the extreme continuously without blowing the fuse then you wil be shortening the lifespan of your amp over time, you probably won't burn it up instantly.

Personally, I don't like replacing fuse constantly, and I don't like to replace my equipment all the time.  Let me rephrase that...I can't afford to replace my equipment all the time, I would always like to come January, but the wife would not approve.

Ok... thanks again everyone for helping explain.For a while there it seemed to be bordering on the absurd..which Is why I mentioned the pet choking thing..a little sarcarsm to lighten things up.

Anyhow...some things I may also need help with on the subject.  Were discussing situations in which voltage fluctuates constantly..such as in a vehicle. I would assume some kind of voltage regulation is used in any 12v automotive amplifer to help compensate..for normal as well has more extreme fluctuations.

But regardless......dealing with this specific post..and my original reply...lets take this example.

Ok..a 400w amp....and a 15ft run of power wire. For the sake of this dicussion I will leave out fusing and other obvious issues..I just want to deal with wire gauge and what I belive the effects should be.

I used math..ohms law and a current draw calulator.I came to these conclusions...

using ohms law@ 12v the maximum current draw should beroughly 33.3a. At 14.4....roughly  27.7. So I averaged the current draw to be 30a @ 400w.

using a 4ga wire..(resistance of .25m ohm per foot) a run of 15 feet will have a Vdrop of  approx. .11v.

An 8ga. (.63m ohm per foot) @ 15 feet = Vdrop of  approx .28v.

A 10ga. (a little under 1ohm for a 15 ft run) should have a Vdrop of approx .44v..less then 1/2 a volt.

And these calculations are maximum assuming max draw at all times.

So I guess where I am going with this is does anyone really belive the difference in voltage drop using the 10ga is really enough to burn stuff up??  The normal voltage fluctuations in a vehicle far exceed the difference in Vdrop caused by the wire gauge...and remember..I am talking about the question from the OP..not hypotheticals or sytems running at 1ohm..or massive current draw that exceeds the limits of conventional charging systems etc.

Now before anyone jumps on me..lol...PLEASE realize I am not trying to arugue that it is ok to use a smaller wire ga. then required..I never do that..as a matter of fact I am notorious for overkill when it comes to audio system wire size...but it is the reason why I use the larger wire we seem to have some differnet opinion about..well at least in the case with this 400w amp.

Where I do have some issue...is believing that in this particular post ..that the extra heat caused by using a 10 ga wire would be substantial enough to cause concern...or should there be concern..but perhaps about as much as a pet choking on a speaker wire..lol sorry had to add that. I do plan on doing some experiments with wire gauge and amp temp in the future..I want to find out how much difference it make as far as heat being a major concern. I won't bother with anything ridiclous like running a 1000w amp off an 18ga..although it would be fun watching the wire insulation burn off..but something similar to this situation where using "border line" wire ga. vs. whats called for  vs. overkill.

Thanks again guys..great stuff.

custom audio ny wrote:

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Where I do have some issue...is believing that in this particular post ..that...

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Please keep in mind that this is a widely read forum whose history has been to provide basic fundamental truths about the workings of car audio.  New members often find answers to their own questions without ever posting, as can be seen by looking through the general membership list at the number of members who never posted a single question.  Answers, generally, are purposefully blunt and to the point.

The gist of this OP's concern is about power wire gauge.  Specifically, he doesn't understand the importance of using the appropriate or recommended gauge, so he asked if it was an issue to be concerned with.  There are other readers who want to know this, too; most with different specifics than those related here.  The answer that you are taking issue with is about basics and encourages all readers to realize the importance of wire gauge.

SoundAudio wrote:

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DYohn answered the power wire precisely for the original question.

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stevdart, I think you may have taken that statement out of context......(that happen here???lol) I didn't mean to imply that anything discussed on this post was not extremely useful information..or that I had "issue" with any replies per say.

The OP simply asked "Will I get better deeper bass by switching to the 4 gauge." I replied in a way that reflects what I have experienced.....more voltage will in most cases..produce more output. And more voltage will definatly be a side effect of using the proper gauge. 

Now others mentioning that he will not notice a difference in bass output.....right there we have debate???  right??

Now there is nothing wrong with debate..and there is nothing wrong with mentioning other factors that come into play when dealing with wire gauge. But when I started reading replies about amplifiers burning up...and wires melting down..well at that point I needed to attempt to put things into perspective.

I would rather people use the proper gauge in any situation....but I will debate anything I either don't understand...don't believe to be true...absurd.. an exaggeration or taken out of context.

Is there anything wrong with that.?..People should learn all sides..not just be frightened into thinking stuff will burn up when it's not going to happen. Or if it is going to happen..I would like some convincing, conclusive evidence.

In closing..I had a disagreement with a reply...should I be shunned from debating? Perhaps this place isn't for me.

custom audio ny wrote:

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In closing..I had a disagreement with a reply...should I be shunned from debating? Perhaps this place isn't for me.

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haemphyst..this is custom audio ny. Apparently someone must have taken something I said personally since the last time I replied here I have not been able to sign in..but it could be a technical glitch as well..I have an email into admin about it. I don't believe I broke any forum rules.

Anyhow I appreciate what you said..it makes me feel alot better about this forum. I as well hope nobody takes anything I post personally as well..it is not my mission to insult or belittle anyone..just to share knowledge. Nobody really knows who I am here..and vice versa so it really would make little sense to get personal regardless.

Ok back to the "debate"..lol. I think where I may have had a problem with this topic is in a few areas. I oversimplified some factors...such as that an audio system consists of a power source...wire..and the amplifiers internal circuitry. I was looking at it more as a simple circuit...such as a light bulb. Now a light bulb has a wattage. It uses power..which is work over time..and given off as heat and light...kinda like an amp (as far as heat) but the similarity stops there.

Now if we lower the voltage going to a light bulb...it gets dimmer and gives off less heat. HOWEVER, if we lowered the voltage to the light by using a wire that was too small..it is basically acting as a resistor...and we all know that resistors use power..hence they heat up. Looking at it this way you still get the same result...less power to the light..so the light itself will not be as bright or warm...regardless of how we lessen the voltage to it.

Now I looked at it this way not taking the amplifiers power supply into account..something the lightbulb does not have..it simply draws what it can to light..up to its wattage rating..lower the voltage..it dims..to much voltage..it burns out..plain and simple.

Now I still stand firmly that a 400w amp can use a 15ft run of 10ga without causing enough heat in the wire to burn it up..but it could get warm if played at max power steadily for a length of time.not a danger..but not something we want..as far as an increase in bass output using a 4ga..I still say possibly enough to notice...but once again depends on the type of amplifier (power supply..class..circuitry etc) ..now rememer what I stated in an earlier post about the normal voltage fluctuations in a vehicle far exceeds the voltage drop of the 10 gauge..in this case.

I highly suggest to click on the link below..it is an excellent and simple read on this topic and after reading it I definatly took away more then I came in with..good stuff and some stuff I simply forgot but was refreshed.

In closing I state..there may be more then one reason to use the proper gauge wire...but no matter how you slice it...use the proper gauge wire. Power loss and heat are 2 things we need to avoid. Proper fusing is a given for safety. If the wire gauge is significantly too small..you do risk meltdowns, blown fuses..and a shortened amplifier life span (thats out to you Sound Audio).

https://www.caraudiomag.com/specialfeatures/0111cae_anatomy_power_amplifier/

temporary name wrote:

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haemphyst..this is custom audio ny. Apparently someone must have taken something I said personally since the last time I replied here I have not been able to sign in..but it could be a technical glitch as well..I have an email into admin about it. I don't believe I broke any forum rules.

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Try deleting the cookies on your computer. They can prevent signing in.

That link you provided is dead. 

I meant to reply, but the time I got around to it, some one beat me to it with a far superior reply.   

DYohn] wrote:

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There is nothing wrong with the account for "custom audio ny." The "temporary name" account has been deleted.   And by the way, many of us have additional information about "who we are" in our profiles if you choose to click them.

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There are a lot of people on these forums who I've come to admire and respect over the years, and if the time comes I've got their backs.  That's about the plain and simple of it.  But there is no way my politely worded post  that preceeded that custom audio ny post can be construed as a public flogging.  It was an explanatory post to an apparently new member.  If subtle hints could be read into it, then I worded it well.

If it truly was humiliating, I should be flogged and forced to go back to using my original forum identity, Bang Bang. 

wirewise wrote:

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I believe "custom audio ny" is "master5". See the following post: https://www.the12volt.com/installbay/forum_posts.asp?tid=91467&KW=master5

~wirewise~

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Ah.

stevdart wrote:

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If it truly was humiliating, I should be flogged and forced to go back to using my original forum identity, Bang Bang. 

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... and I'm NoUse.