how much power...

how much power can my puny stock alternator put out? its a brand new 2002, and i want to put the biggest amp in there without draining my battery :p

imma take a guess at this and say its about 85amps.

you mean watts? damn, screw that im going for 500 :P

Originally posted by Xplosive_Sheep
you mean watts? damn, screw that im going for 500 :P
nope he ment amps... and you can get rewound ones that put out like 130amps

if ya wanna know how much power u will get out from 85amps then use:

Power (Watts) =Voltage (Volts) x Current (Amps)

so how do i figure out how many volts my car can handle so that i can figure out how many amps i can have ??????

well thats where you need a voltmeter, unless it says the output on it somewhere. Unless you can measure it then youre gonna get all confused in a mass of sums that are gonna end up with you needing to measure something in the end anyway

daaaaang, im way to lazy to do all this work, i think that at 450watt amp should do just nicely, my bro has had one for a long time and it hasnt drained his battery, wish me luck:D

well, that gives you the absolute power ........... 14 volts X 85 amps = 1190 watts. But amps are not a static load like say headlight. The power an amp pulls is more in pulses ......... but a 1000 watt RMS amp only pulls only like 100-200 watts of average power. You should be able to run 1200-1500 watts of power with no problem.

It won't drain your battery. Your headlights will just dim whenever the bass hits, it might drop your rpm's a lil too, but not enough to stall you or anything. To fix the problem just get a capacator or two. They sell Rockford-Fosgate 1 farad capacators at Best Buy, for like $100 a piece. Just make sure you get them professionally installed because if you don't charge them before you put them in, they can explode.:bloated:

are you two absolutly sure?? cause from what i have heard before completely contradicts what you said...man now i am even more confused :eek:

Originally posted by colechaney
It won't drain your battery. Your headlights will just dim whenever the bass hits, it might drop your rpm's a lil too, but not enough to stall you or anything. To fix the problem just get a capacator or two. They sell Rockford-Fosgate 1 farad capacators at Best Buy, for like $100 a piece. Just make sure you get them professionally installed because if you don't charge them before you put them in, they can explode.:bloated:

caps are useless: http://pub51.ezboard.com/fcaraudioknowledgefrm7
read the truth about caps there. i run a 800watt system with no dimming at all (full blast).

i guess i dont know enough about audio to understand, but my brother runs a 450x1 on a 12 bandpass and he gets his civic headlights dimmed everytime there is a big bass note....

it's not really "audio" ... it's physics. If a source, like an amp, draws more power than the alternator can provide - the voltage of the system will start to droop (lower). Amps with real stiffly regulated power supplies can make this even worse, since as the voltage drops it increases it's current demand to keep the power input constant (power = voltsXamps). For some car/amp combos, a capacitor can help to stiffen up the electrical system and prevent those voltage droops when the bass hits that cause the headlights to flicker with the beat of the bass, for others - they do nothing. NOTE: capacitors do NOT increase your SPL or the subjective sound quality.

I have a completely different question, but I'll ask you guys since you seem to be a knowledgabe bunch. Why do you need so many watts in a car stereo. I have a many stereos in my house, both solid state and vacuum tube and none of them is over 80 watts, except the surround sound amp, and that is only 250x5, or 50 watts per channel. All of the stereos in my house run on extremely efficient speakers and the sound quality is great. Infact, the Dynaco Dynakit Tube amp is the best sounding, and probably puts out no more than 30 watts a side running on a set of Electro Voice speakers. I also have a Fender Dual Showman, it's a 100 watt single channel guitar amp pushing 2 15" speakers. So my question again is why the need for extreme power in such a small car with such small speakers?

Really you don't need -that- much power. Home audio gets away with using very little power because the acoustics in a room are way better than the acoustics in a car. There is more air to push around, and there are more places for you to put your speakers for better sound staging.
in my car i've only got a 800 watt 4 chan. amp to power two 12"s and a pair of componets. i'm probably putting about 130-150RMS to each sub and between 50-75 RMS to the front speakers (no rear speakers so i have front sound staging). Time and time again i've had people tell me i have one of the loudest systems they've ever heard. IMO the power isn't what makes the system loud. I've found great speaker placement and well made boxes can more than make up for the lack of power an amp is pushing. if you get your speakers door speakers to point at your dome light vs. at your feet it'll be louder and sound cleaner. things like that go unnoticed, but help a lot.
Also i very well made box will own someone with a shitty box and a big power amp and subs. I saw a guy with three 15" kicker subs (those square ones.. solobaric or something like that i believe) pushing almost 400 watts to each make less dbs than someone with a 12" sub in a -perfect- bandpass box with a 100 watt RMS amp. of course the one with the bandpass box was made for sound comps and he knows his stuff, but my point is you can make up power with a good box and good speaker placement. Those three 15"s should eat everyone's lunch, but because almost no one is building good boxes for them yet, they sounded like hammered ass.
sorry for long post, i hope it helped

Originally posted by luti
I have a completely different question, but I'll ask you guys since you seem to be a knowledgabe bunch. Why do you need so many watts in a car stereo. I have a many stereos in my house, both solid state and vacuum tube and none of them is over 80 watts, except the surround sound amp, and that is only 250x5, or 50 watts per channel. All of the stereos in my house run on extremely efficient speakers and the sound quality is great. Infact, the Dynaco Dynakit Tube amp is the best sounding, and probably puts out no more than 30 watts a side running on a set of Electro Voice speakers. I also have a Fender Dual Showman, it's a 100 watt single channel guitar amp pushing 2 15" speakers. So my question again is why the need for extreme power in such a small car with such small speakers?

Thanks, but I still don't understand why the amount of watts seems to go from a seemingly small number (sub 100) to an almost exponential amount (past 500). Are they amps rated differently? Are the speakers being used in cars rated differently? What are distortion ratings on these amps, and how long a duration is the 500 (or 800 in your case) watt rating for?

Your runnin 800 watts, and your lights don't dim at all? Do you have a secondary battery, or a beefed up alternator?

Time and time again i've had people tell me i have one of the loudest systems they've ever heard.

Those people must have never been to a db drag event/car show. Not to diss but 800 watts isnt really alot when you look at some of the other stuff that's out there.

i agree with him^ i dont see how you can run 800 watts and not have your headlights dim when you crank it

my system has a lot of power and i usually dont have a problem with dimmed lights when the bass hits. I run 1000watts max (5 or 6 hundred RMS) and i have never had that problem. I think a second battery is really not necessary unless you are running over about 1500, otherwise a cap would be a much simpler set-up

Originally posted by colechaney

Those people must have never been to a db drag event/car show. Not to diss but 800 watts isnt really alot when you look at some of the other stuff that's out there.

you are correct, none of them have been to db drag event, and i'm not saying my car is by any means the best. Since getting my car back from being painted i have been to three major shows, one of which was a NOPI show (think fast and furious style show cars). I'm very aware of what is out there. my point was that power isn't everything. with an 800 watt system people i've met think i hit harder than a car with a 1500watt+ system. It's because the boxes i have are custom made to hit clean and hard. even at the shows with the big ass systems, what seperates the winners from the losers is who builds the best boxes.

My whole point is don't spend all your money on a great sub and amp and then get all cheap ass on the box. I say a super box is worth twice as much as a nice amp and subs.

Originally posted by colechaney
Your runnin 800 watts, and your lights don't dim at all? Do you have a secondary battery, or a beefed up alternator?

no extra battery not beefed up alternator. I drive around w/o my AC on so that might have something to do with it.. sometimes i'll have AC at 1 but i still never have problems. The -only- time i ever notice dimming is if i've left my system on w/o running my car for one hour+. once i run my car for a few min it's back to normal. If anyone lives in the north dallas area come out to coit and park in Plano.. we have a little car meet there every night just out of boredom. I think there is too much myth about dimming lights etc.. if your light are dimming (noticably) when you bass hits, i'd suggest checking all your grounds for your car. there's no way a little 75AMP amplifer should be able to pull too much current from your battery.

Someone also mentioned a cap..i think it was "so-cali"... thanks for contributing to my point that someone running about 1k watts+ and still doesn't having dimming problems, but i do need to dissagree with you about the second battery not being necessary and a cap being better. at http://pub51.ezboard.com/fcaraudioknowledgefrm7 it explains in the faq about caps how they are useless. They are mearly a $100 car audio decoration. i have seen systems in the "unlimited" class at car audio comp that need more than one bettery. for daily driving no one could possibly have a system that merits a second battery (unless they are deaf), but for db drags, a second bettery is much better and more useful than a puny little cap.

Luti .... home amps are into 8 ohm loads, car stereo amps are rated into 4 ohm loads - a 50 watt home amp is the same as a 100 watt car amp. In a car (that's moving), the ambient noise is quite high - typically around 70-75 dB, If it gets loud at home - you can always send the kids away. The latest trade-off that car subs have made was volume (space) for power, we no longer need a 5 ft^3 box for good bass - most need about 1-1.5 ft^3 ..... but they have doubled to quadrupled the power handling. This is not really a problem anymore, since a class D amp makes power cheap - 1000+ watts for less than $400. Most home theater stuff does not really require much power ....... and most home speakers tend to be a good bit more efficient than car ones. So really, you are comparing apples and oranges.

ACCSlvCivic ...... having more space in a room would make them LESS loud, not more

Adding a battery to a "street" system will TAKE power from the system when the car is running. When the car is running, the alternator provides ALL of the power for the car until a load drags the voltage down to the level of the battery. Unfortunately, due to the relatively high ESR of the battery, I wouldn't count on it for much help. The only real need for extra batteries is for SPL burping.

Originally posted by PaulD

ACCSlvCivic ...... having more space in a room would make them LESS loud, not more


that's true, however because you have more room you have more flexiblity in your speaker placement. it doesn't matter how loud a speaker is if it isn't pointing at you. more space would mean less loud unless that extra space was used to increase effiency of placement.

it is true that you can use the corners of a room to make a corner reflector, to increase efficiency - but the main point of home stereo is that you have a LOT more flexibilty in postioning the speakers and listeners. This greatly effects the qaulity of the sound, but doesn't do anything for the actual max volume.

P.S. rarely do you point the main speakers directly at the listeners .... although off-axis output of a speaker is not that greatly reduced.

one of the worst places to be is directly infront of the speaker due to the way the sound refracts at an angle

Originally posted by PaulD
it is true that you can use the corners of a room to make a corner reflector, to increase efficiency - but the main point of home stereo is that you have a LOT more flexibilty in postioning the speakers and listeners. This greatly effects the qaulity of the sound, but doesn't do anything for the actual max volume.

P.S. rarely do you point the main speakers directly at the listeners .... although off-axis output of a speaker is not that greatly reduced.


My i guess i didn't catch everything my friend explained to me when he was tlaking about him home audio. The way he had it set up was with front speakers pointing at the couch, and the rear speakers set to bounce off the back wall of the room and to the couch (an equal distance away.

i've heard of people using that same theory in car audio by hooking up their rear deck speakers out of phase in order to bounce the sound off the glass. i don't recall the term for that... 3 hours of sleep for a week straight ruins your memory!

actual max volume isn't changed, but correct me if i'm wrong, freqs greater than 100hz (i'm pretty sure) are directional. if you speakers are pointing straight into a wall, the speakers are not going to be as loud as they would if you pointed them straight at you or angled them to bounce off the wall and at you.

Originally posted by ACCSlvCivic



My i guess i didn't catch everything my friend explained to me when he was tlaking about him home audio. The way he had it set up was with front speakers pointing at the couch, and the rear speakers set to bounce off the back wall of the room and to the couch (an equal distance away.

i've heard of people using that same theory in car audio by hooking up their rear deck speakers out of phase in order to bounce the sound off the glass. i don't recall the term for that... 3 hours of sleep for a week straight ruins your memory!

actual max volume isn't changed, but correct me if i'm wrong, freqs greater than 100hz (i'm pretty sure) are directional. if you speakers are pointing straight into a wall, the speakers are not going to be as loud as they would if you pointed them straight at you or angled them to bounce off the wall and at you.

Sounds like you are on the right track here .... the corner reflector is for bass only - the actual speakers cones are pointed into the room. The off axis response is a measure of loudness (and freq response) with the mic somewhere other than right in front of the speaker. And yes, frequencies above 90 Hz or so start becoming directional - that's why pods are so functional in a car. You aim the speakers at the dome light (for those cars whose dome lights are just behind the rear view mirror). This means that the closer speaker is just a little more off-axis than the far one, so it equalizes it out a little.

In home theatre, there is no need to turn the rear speakers backwards, since the material going to them already has the lowered signal and ambience put in electronically. In a car, you can get the sound of rear fill speakers if you have a hatch and play with the speaker placement a little (or get lucky). The sound will bounce off the rear glass and make a "phantom" rear fill ... meaning it will sound like you have rear fill speakers when you really don't. One judge told me I needed to turn up my rear fill speakers, his teeth just about fell out when I told him there were no mid/tweeter speakers behind the front seats - I guess he felt like a fool after that one.

thanks, i learned something new :) your a baddass :smoka:

hey, I learn stuff on here (and a few other forums) all the time