# after the big three whats next?



## matttatts (Sep 16, 2008)

i think my battery is tired so im probly gunna have to replace it but is there any order i shud do this in? 

like alt furst? then battery or vice versa?

input plz


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## Jeff Rohrer (Jul 9, 2010)

Battery first, always cheapest things first. You never spend 500 on an alternator and that not be the problem. I know I'm dumb-ass for suggesting to use math first but....What amp/s are you running? I would add there rms wattage up at there lowest impedance. Once you have the highest possible rms wattage then you can rough guess on your amperage based on what type of amps they are...Class D, AB, and so on. If there Class D you guess about 70% efficiency so if you had a 1000watt rms amp then it's max pull in amps would about 40-50 amps max. If you need help figuring this all out then pm me. I know it's just easier to start buying things because the internet tells you so but why not learn?


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## 87gbody (Dec 20, 2007)

:h5:


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## matttatts (Sep 16, 2008)

Jeff Rohrer said:


> Battery first, always cheapest things first. You never spend 500 on an alternator and that not be the problem. I know I'm dumb-ass for suggesting to use math first but....What amp/s are you running? I would add there rms wattage up at there lowest impedance. Once you have the highest possible rms wattage then you can rough guess on your amperage based on what type of amps they are...Class D, AB, and so on. If there Class D you guess about 70% efficiency so if you had a 1000watt rms amp then it's max pull in amps would about 40-50 amps max. If you need help figuring this all out then pm me. I know it's just easier to start buying things because the internet tells you so but why not learn?


i am running two 1000 wat D class kenwood amps. i DMM them out and the amp is seeing 2.3 ohm.

i have one more fosgate amps to go in for the interior speakers with a 40 amp fuze so 400 rms? ill wire it two a 2ohm load also. 
havent botherd putting it in yet as the two subs are drawing enough on my system already.

id love to learn thats why i ask! :biggrin: unfortunatley tho im a highscool drop out and my math skills suck :sad:


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## Jeff Rohrer (Jul 9, 2010)

matttatts said:


> i am running two 1000 wat D class kenwood amps. i DMM them out and the amp is seeing 2.3 ohm.
> 
> i have one more fosgate amps to go in for the interior speakers with a 40 amp fuze so 400 rms? ill wire it two a 2ohm load also.
> havent botherd putting it in yet as the two subs are drawing enough on my system already.
> ...


 I dropped out as well, but I went to college, not that it makes me better because it doesn't. Well like I said the math is pretty easy. I just get sick of seeing people give the same bull crap advice "Buy a cap, buy two batteries, get a 250 amp mechman alternator, do the big three" I have a 2000rms amp and 1200rms amp in my stock civic. No extra batteries, no upgraded alt, no big three and no lights dimming! Always add up total power usage then find out what amp your vehicle's alternator is if you can. I'm not saying doing the big three wont help or that its unnecessary, but it's not always necessary. 

Ok well for your sub amps which model are they because that matters. If there designed to put 1000rms @ 1 ohm and running them at 2.3 then your subs are seeing much less then 1000 and the amp is not running near full it's capability which means it pulling way less power. Can post a complete list of model numbers and amount? like dual voice coils, two subs, three amps ect. ect.?


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## matttatts (Sep 16, 2008)

Jeff Rohrer said:


> I dropped out as well, but I went to college, not that it makes me better because it doesn't. Well like I said the math is pretty easy. I just get sick of seeing people give the same bull crap advice "Buy a cap, buy two batteries, get a 250 amp mechman alternator, do the big three" I have a 2000rms amp and 1200rms amp in my stock civic. No extra batteries, no upgraded alt, no big three and no lights dimming! Always add up total power usage then find out what amp your vehicle's alternator is if you can. I'm not saying doing the big three wont help or that its unnecessary, but it's not always necessary.
> 
> Ok well for your sub amps which model are they because that matters. If there designed to put 1000rms @ 1 ohm and running them at 2.3 then your subs are seeing much less then 1000 and the amp is not running near full it's capability which means it pulling way less power. Can post a complete list of model numbers and amount? like dual voice coils, two subs, three amps ect. ect.?


ya man!!

i have two sub amps these here
Kenwood - KAC-8105D

the subs they are running. each in its own seprate box.
Kenwood - KFC-XW1224D

for my interior i have a RF amp i have yet to hook up on account of my curent power draw problems
Rockford Fosgate® - P325.1


runing off the deck curently i have..


two 6x9 kenwoods in the rear shelf
Kenwood - KFC-X692

and two focals one in each door.
Focal Access 130CA1 5-1/4" 2-way car speakers at Crutchfield Signature


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## Jeff Rohrer (Jul 9, 2010)

Ok, so with all amps connected and running at there lowest impedance you have a net total of 1325 watts rms. Assuming all three amps had no efficiency you would have a total amperage draw of 130 amps. However your sub amps are Class D and the punch amp is a class BD which all three have good efficiency so guessing would put actual amperage draw around 70-80amps. So next I would ask what vehicle is it? and when you replace the battery you'll most likely see the dimming go away, just make sure all of your amps are grounded to the same location and make sure there all clean grounds and very tight.


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## DARKJUGGERNAUT (Apr 14, 2004)

another question how did u do big three and what size wire...


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## 79 cutty (Sep 27, 2005)

DARKJUGGERNAUT said:


> another question how did u do big three and what size wire...


1. Upgrade your battery Ground (battery negative terminal to chasis ground)
2. Upgrade your engine block ground (engine block to chasis ground)
3. Upgrade your alternator wire (battery positive to alternator)

If you plan on upgrading your system just go with 1/0 from the start...otherwise if you are running 4 ga, just go with that.


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## matttatts (Sep 16, 2008)

Jeff Rohrer said:


> Ok, so with all amps connected and running at there lowest impedance you have a net total of 1325 watts rms. Assuming all three amps had no efficiency you would have a total amperage draw of 130 amps. However your sub amps are Class D and the punch amp is a class BD which all three have good efficiency so guessing would put actual amperage draw around 70-80amps. So next I would ask what vehicle is it? and when you replace the battery you'll most likely see the dimming go away, just make sure all of your amps are grounded to the same location and make sure there all clean grounds and very tight.


its a 1970 cadillac.

i dont think i can ground my RF amp to the same spot. im hidding it under the rear deck cuz it doesnt match my outher amps. it will be a long wire to ground it to the same place as the outhers

so how does the amps efficancy lower its amp draw?



DARKJUGGERNAUT said:


> another question how did u do big three and what size wire...


i used 4g


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## Jeff Rohrer (Jul 9, 2010)

The efficiency has to do with what type of circuit it is. Class D circuitry by design is very efficient and so is Class BD which is the type of circuit design the punch amp is.


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## L.Daco1 (Jun 16, 2010)

Your working your efficiencies backwards. The amp will still pull the same current at any given point but only (insert your efficiency percentage here) of that current will be used to create the output. The other x% will most likely be lost as heat.


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## Jeff Rohrer (Jul 9, 2010)

L.Daco1 said:


> Your working your efficiencies backwards. The amp will still pull the same current at any given point but only (insert your efficiency percentage here) of that current will be used to create the output. The other x% will most likely be lost as heat.


What?


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## L.Daco1 (Jun 16, 2010)

Let's say your amp is pulling 100A at 14.0V, this would equal an output of 1400W, but as we all know no amps are 100% efficient, so this is where the efficiency rating comes into play. Let's say that at 4ohms your amp is 70% efficient, so it would put out 980W. At 2 ohms, let's say the efficiency rating is 60%, then the output is 840W. The point is, the input voltage and current draw is the same. The only thing that changes is the output which is dependent on the impedance of the load and the amp's efficiency. At lower impedance the efficiency level is worse. Fluctuations in the speaker's inductance as well as the mechanical interactions between the box and the speaker make for a dynamic environment in which impedance and thus the amp's efficiency is always changing. The bottom line is efficiency ratings have nothing to do with how much current an amp pulls. The easiest thing to do is to just go by the fuse ratings of the amplifier, as you know the amp will not see a load above that rating. The sum of all the fuse ratings will give you a good estimate as to how much current your system will consume. Just add this number to what the car's stock electrical system will pull and then subtract the amount of current the alternator will put out and it gives you an idea of what kind of deficit you have to make up. A voltage gauge can also help out quite a bit. If you're playing your setup at full tilt and you immediately notice big voltage drops then you know your charging system needs to be upgraded. Personally, I would invest in an HO alternator and at least one decent battery and go from there. I'm not suggesting he should go out and buy a 300A alternator and 4 d3100s but the alternator is the most important part of the electrical system (at least while the car is running) and if you throw a bunch of batteries on a stock alternator then it will fry your alternator pretty quick as well as kill the batteries. Also good electrical will help keep the voltage stable and will help to keep the amps from clipping.


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## DARKJUGGERNAUT (Apr 14, 2004)

matttatts said:


> its a 1970 cadillac.
> 
> i dont think i can ground my RF amp to the same spot. im hidding it under the rear deck cuz it doesnt match my outher amps. it will be a long wire to ground it to the same place as the outhers
> 
> ...


 4 gauge is from ditribution to amp u need 1/0 min thats ur problem do all 1/0 and it will b better..than let us know where u r..BUT DO THE 1/0 FIRST ALL THE OTHER RESPONSES WONT HELP UNTIL U DO THE 1/0 WIRE AND GT A GOOD BRAND NOT ANY INSTALL BAY SHIT..knu konceptz is good wire..


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## L.Daco1 (Jun 16, 2010)

4AWG is sufficient for this setup. His Kenwoods pull about 35A each and the Fosgate will pull around 40A for a total of 110A. Decent car audio 4AWG should handle up to 150A. Also he's running a 140A alternator. Although I do believe that more is better, especially in upgrading your electrical system, 1/0 is not necessary for this build.


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## matttatts (Sep 16, 2008)

DARKJUGGERNAUT said:


> 4 gauge is from ditribution to amp u need 1/0 min thats ur problem do all 1/0 and it will b better..than let us know where u r..BUT DO THE 1/0 FIRST ALL THE OTHER RESPONSES WONT HELP UNTIL U DO THE 1/0 WIRE AND GT A GOOD BRAND NOT ANY INSTALL BAY SHIT..knu konceptz is good wire..


whaa?i dont know what that is?

now im confused sorry


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## BIG DIRTY (Jan 31, 2002)

L.Daco1 said:


> Let's say your amp is pulling 100A at 14.0V, this would equal an output of 1400W, but as we all know no amps are 100% efficient, so this is where the efficiency rating comes into play. Let's say that at 4ohms your amp is 70% efficient, so it would put out 980W. At 2 ohms, let's say the efficiency rating is 60%, then the output is 840W. The point is, the input voltage and current draw is the same. The only thing that changes is the output which is dependent on the impedance of the load and the amp's efficiency. At lower impedance the efficiency level is worse. Fluctuations in the speaker's inductance as well as the mechanical interactions between the box and the speaker make for a dynamic environment in which impedance and thus the amp's efficiency is always changing. The bottom line is efficiency ratings have nothing to do with how much current an amp pulls. The easiest thing to do is to just go by the fuse ratings of the amplifier, as you know the amp will not see a load above that rating. The sum of all the fuse ratings will give you a good estimate as to how much current your system will consume. Just add this number to what the car's stock electrical system will pull and then subtract the amount of current the alternator will put out and it gives you an idea of what kind of deficit you have to make up. A voltage gauge can also help out quite a bit. If you're playing your setup at full tilt and you immediately notice big voltage drops then you know your charging system needs to be upgraded. Personally, I would invest in an HO alternator and at least one decent battery and go from there. I'm not suggesting he should go out and buy a 300A alternator and 4 d3100s but the alternator is the most important part of the electrical system (at least while the car is running) and if you throw a bunch of batteries on a stock alternator then it will fry your alternator pretty quick as well as kill the batteries. Also good electrical will help keep the voltage stable and will help to keep the amps from clipping.


Nice!!!!

LD is right, and 110 amp draw should be good for 4 awg. But I am looking at that Alternator, and I do not think you got another power coming out that Alternator, looks like maybe 90 amps max. What type of Vehicle.


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## BuThatsaCHRYSLER (Mar 19, 2002)

BIG DIRTY said:


> Nice!!!!
> 
> LD is right, and 110 amp draw should be good for 4 awg. But I am looking at that Alternator, and I do not think you got another power coming out that Alternator, looks like maybe 90 amps max. What type of Vehicle.


ding ding ding, its a 1970 deville, which i have owned 3 of. I agree with needing to total up your draw to determine what steps need to be takin, but that looks like a factory alt and is deffinetly not putting out 140a i would say considerably closer to 80a


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## L.Daco1 (Jun 16, 2010)

BIG DIRTY said:


> Nice!!!!
> 
> LD is right, and 110 amp draw should be good for 4 awg. But I am looking at that Alternator, and I do not think you got another power coming out that Alternator, looks like maybe 90 amps max. What type of Vehicle.


Yeah, I'm thinking that the alternator is the problem too now. With just the 2 Kenwood amps he's pulling 70A. Even if that is a 140A alternator this accounts for half of the alternator's output. Most stock alternators are meant to supply the vehicle's stock electrical system plus ~30%.


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## DARKJUGGERNAUT (Apr 14, 2004)

his electrical is not capable either even w a 140 amp im not goin to right a journal of y it wont.so many variables r bein missed and not accoounted for..


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## Jeff Rohrer (Jul 9, 2010)

Ok, so after the big three your going to want to get one of THESE, yes it's a little pricey but totally worth it. You'll have enough power for that crazy system of yours and you'll have the ability to travel back and forth through time. It's win - win!


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## Jeff Rohrer (Jul 9, 2010)

Also it would hurt ya to get a set of THESE:loco::machinegun::thumbsup::ugh::dunno:


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## bigdoggfromaz (Aug 28, 2008)

:thumbsup:


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## L.Daco1 (Jun 16, 2010)

Jeff Rohrer said:


> Ok, so after the big three your going to want to get one of THESE, yes it's a little pricey but totally worth it. You'll have enough power for that crazy system of yours and you'll have the ability to travel back and forth through time. It's win - win!


Finally a cap worth buying!
:thumbsup:


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## Jeff Rohrer (Jul 9, 2010)

L.Daco1 said:


> Finally a cap worth buying!
> :thumbsup:


I know right? No more pesky arguments on whether they work or not and are worth it!


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