So I've searched and can't seem to find this question. What's a good alternator for running a pair of subs in a 74? They're so many ho alts so which one's have been tried and work well? Thanks in advance for any help.

It's not the subwoofer that determines the alternator output needed but the total electrical system draw.

You need to do the math on the entire automotive electrical system and the audio system then add them together!

If you have a cheap brand of amplifiers and signal processors, they will be inefficient and draw more amps at peak use and create more heat and not work properly.

Many people are converting over to the SI unit with 105 amps as a start but you can also look at some of the high end audio custom oversized units but will cost you more!

You have a world of information missing.

I suggest you figure out what subs you want and call the manufacturer.

I guess I didn't explain myself well enough. Basically what I'm wondering is what brand of ho alt are people running that they've had good results with while powering an amp in an aftermarket system. I'm still undecided on what brand I'm gonna run, most likely will stick with re audio and around 1000w system. I just know there are some junk ho alternators and didn't wanna waste money weeding them out.

I just did CS130 upgrades on both my 1970 442 and 1978 Camaro.

Technically I have a LS1 in my Camaro and it came with the CS130.
Both are 140amp.

I found a guy on Ebay who can custom make any CS130 to fit your application in chrome for around $130
Measure your housing, and email him and tell him you need it for a V-belt.
http://cgi.ebay.com/ebaymotors/NEW-Chrome-GM-140-amp-1-or-2-wire-CS130-TPI-alternator_W0QQcmdZViewItemQQhashZitem35a823e581QQitemZ230454191489QQptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories

Varying people have opinions on what kind of size (amp output) alternator you will need.
I will tell you flat out, I've done high end stereo installs with 200amp alternators in newer cars
and 140amp in classics. We've killed a few because we didn't have big enough power.

So you need to figure out how many amps you're using first, and TRUE POWER, not BS Sony or JVC power ratings.
I like Kicker amps now, so I called them directly to ask how much amp pull each needs max and I based my
builds off that. That's why I said, call the manufacturers, instead of taking the opinions of a few car guys
who have basic car stereo installs. No one will know unless you list your amps, and even then most won't know.

Once you add a pair of quality subwoofers and after market 4-6 stereo speakers, you're not the norm anymore.
A stock 63 amp alternator isn't going to cut it. I believe in creating enough overhead the 1st time to have room to expand.
Electric fans, 3rd brakelights, newer GM Mirrors, etc.

The other thing is that subs by themselves draw zero (0) amps. It's the amplifier that does all the work. Look at the size of the fuse on the amplifier to know what the maximum draw is on it to help figure your needs. I'm running a 94A alternator from an '85 Camaro, and it bolted right in.

The other thing is that subs by themselves draw zero (0) amps. It's the amplifier that does all the work.

Yep.

That's why just saying "A subwoofer" isn't telling anyone anything. Subs have so many levels of power and quality, and IMO you should choose
what subs and speakers you want first, then choose the amp(s) you need to power them all, THEN you will be able to choose what size alternator you will need.

I just get 140amps because I know I'm going to be using at least 1 amp, electric fans, maybe HID's down the road, etc.
IIRC Kicker told me I'd have to upgrade my alternator again if I wanted to go with 2 subs as well.
It just depends on what amps you choose like Batman said.

There are so many different sources for alternators it would be hard to name just one. I always used Ohio generator in my competition vehicles. I used to run 2 240amp alts.

The other thing that you have to check is the power supply on the amplifier you're going to use. If the power supply is un-regulated (like an Orion HCCA) then you'll need a HUGE alt. If you're using a regulated power supply amp, then you can go smaller. If you're utterly concerned you can use a 1 farad capacitor just before your amp on the power wire. The cap will store the energy for the bass hits to prevent light dimming.

My show/ demo truck used to be a 1990 Nissan. I kept the factory alternator, added dual isolated batteries and a 1 farad cap. The system was 3300 watts RMS using all MTX Thunder amps. The lights never faded and I could run that thing all day with no issues.

I run my stock 140amp Alt in my impala with 600watts between two amps with two 7x10s, two 6.5s two 1 inch tweets, 1 7 speaker center channel and two 12 inch subs, HIDs and 6 whelen police strobes. no issues.

and 6 whelen police strobes. no issues.

Now why would you put those in ?? Just to mess with people ???

Now why would you put those in ?? Just to mess with people ???

heh, i used to have strobes on my blacked out lumina (car not van). Was pretty cool, car was black, tinted windows all around, and stobes in the headlights. Novelty wore off pretty quick though.

When your at a car show with anywhere from 10 -15 Black Impalas you need to stand out some. there 4 up front(2 white in the corner lenses, 1 red and 1 blue in the parking lights, 2 white in the rear back up lights. I have a flash controller under the dash the controls which set I turn on and the flash pattern. Red and blue on one switch the other 4 on another.

Yes, I have screwed with my friends with them at night. LOL

I have also use them on accident scenes( not the red and blue) to warn traffic. I always got a thumbs up from PDs for them and sometimes they were jealous of them because mine were brighter than theirs. Most PDs use/d 60 watt strobes, mine are 90 watt. But the LEDs they have now make mine look dim.

is it possible 2 overload the hole system wth 2 big of amp? jst wondering cause i dont want 2 fry any thing if im not using all the big amps & speakers yet.

is it possible 2 overload the hole system wth 2 big of amp?

Yes.

If you tried to power up a C130 Air Force plane with your homes electric box.......same concept. ;)

That's why it's important to choose your
1. Speakers first.
2. Amps needed to properly power them next
3. Alternator needed to power up the amps properly without "brownouts" and not charging the battery enough. ;)

Building a stereo the right way isn't just bump and run, it takes planning.

The easiest way to get good sound with minimal power is to look for speakers that have a high sensitivity rating.

E.G.

These Alpine Type "E" subs have a sensitivity rating of 84dB.
http://www.crutchfield.com/p_500SWE1043/Alpine-SWE-1043.html?tp=111

Where these Pioneer "Champion Series" subs have a sensitivity rating of 93dB.
http://www.crutchfield.com/p_130TSW253R/Pioneer-TS-W253R.html?tp=111

What does this mean to you?

The sensitivity of a speaker is measured at one watt/one meter away (Not sure what frequency is used. Perhaps "Pink Noise"). Decibels (dB) is a measurement of the Sound Pressure Level (SPL).

As a rule of thumb, sound is perceived as being detectably louder (by the human ear) with every gain of 3dB. A sub with a sensitivity of 93dB is 9dB louder than a sub with a sensitivity of 84dB.
I.E., it's more efficient.

Another rule of thumb is, the amount of wattage to obtain a 3dB increase from a speaker is by a multiple of 2.
1 watt, 2 watts, 4 watts, 8 watts, 16 watts, 32 watts, etc.

So right from the get go, you'd have to run 8 watts to the Alpine Type "E" in order to get the same SPL as the Pioneer "Champion Series".

To give a more realistic comparison, the Pioneer will put out as much bass with 100 watts as the Alpine will with 800 watts. That's a somewhat inaccurate comparison, and there are many factors which I haven't mentioned that can skew the results, but you get the general idea.

Another way to gain efficiency is to use a vented chamber (or "ported box"). In rare cases there can be a gain of 6dB of SPL when using a vented chamber over a sealed chamber, but the general average is 3dB. The drawback from using a vented chamber over a sealed chamber is the recommended size of the chamber is normally doubled.

E.G., The Pioneer sub's recommended volume for a sealed chamber is .65 cu/ft.
For a vented chamber, the recommended volume is 1.25 cu/ft.

The Alpine sub varies a little more, but that's because Alpine is giving more vague specs as to which frequency the box is tuned.

Don't go outside the company's recommended volume per chamber, unless you really know what you're doing, or have the available resources to determine what the output of the sub will be.

The other drawback of a vented enclosure is if the frequency range of the music drops below the frequency of what the box is tuned for, the sub can be severely damaged. It will act as if it isn't in an enclosure at all. A sealed chamber is the safer bet.

To sum it up, you can easily get loud, clean, accurate music without using big amps which are going to heavily tax the car's electrical system. Speaker selection is key.

Also, on a side note, this information also applies to the sensitivity of an amplifier. The higher the sensitivity, the more efficient the amp. This has a bigger effect on how clean and accurate the music is, more-so than how loud the music is, but as with many things, the cleaner the music is, the less power it requires to "sound good".

can u have 2 big of an alternator 4 what other componants ur running? ie;140, 180, or 200amp alt?

can u have 2 big of an alternator

Yes.

Think about what you're asking.
If you overcharge a battery, can you ruin it ??? Yes.

Read #9
http://www.batterystuff.com/tutorial_battery.html

Most of your electronic devices have intelligent charging systems that
turn the charging off once the battery is full. An alternator isn't an intelligent
device , it continuously charges the battery.

The alternator is a battery charger. It works well if the battery is not deeply discharged. The alternator tends to overcharge batteries that are very low and the overcharge can damage batteries.

If you're going to be sitting with the stereo on and the car isn't running, this is more likely to happen.

I can't agree with "too big of an alternator can damage a battery". Amps are a measurement of current flow. Once the stored voltage in the battery measures that of the output voltage of the alt., current flow stops.

Remember, all the amperes come from the battery. The alt. just replaces what the battery has lost. If the alt. can't keep up with the current demands of the electrical system the battery loses its charge and the alt. fights to keep up. This can shorten the life of an alt. and the life of the battery.

The only way you could possibly damage a battery by using too large of a alt. is if the output voltage is too high.

If your intention is to sit for long periods of time with the stereo on and the car not running, get a marine battery (deep cycle) and hook it to the amplifiers and hook it to the alt. with a battery isolator. This will keep on battery from draining the other.

..... An alternator isn't an intelligent
device , it continuously charges the battery.

Alternators may not be intelligent but they aren't stupid. ;)
They have an internal or external voltage regulator within the system to prevent overcharging.

If that particular portion of the electronics within the alternator stops working.... It will overcharge in a real big way. High Voltage! :eek:

I replaced my alternator with one which had a defective regulator....
I started the car, tapped the throttle and the volt meter needle buried in the red, the ignition misfired, engine killed and my ignition module was toast.
It took about 5 seconds to kill the module with 20+ volts.
Luckilly, everything else in the car seemed undamaged.

LOL I did something similar.

My wife used to drive a '93 MX6 LS. Decent car. Anyway, I noticed the voltage gauge was a little on the high side, and some things just weren't working right. I suspected it was the voltage regulator but I couldn't leave well enough alone. I had the wife come out and start the car so I could test the voltage on the battery terminals. It read ~16 volts.

Then I had a brain cramp. I thought "Well if the alt. is going bad the car should die when I unhook the battery, right?"

That's only true if the alternator ISN'T charging.

The RPM's shot up (She said around 5,000 RPM), the windshield wipers came on, the horn started to blare and the smoke rolled out from the CD player.

I just about dropped a load right there. LMAO!!!

I managed to keep the leads to the voltage meter on the negative terminal before I jumped out of my skin and just caught a glimpse of the LCD display. It read just over 21 volts!!!

Luckily she was smart enough to kill the engine before any more damage was done.

She saw me jump so high she thought I got electrocuted. "Are you OK? Are you OK?" Of course my response was "No. Hold on." but that's just because my heart was racing at 1,000 BPM.

Good times. ;)

Alternators may not be intelligent but they aren't stupid. ;)
They have an internal or external voltage regulator within the system to prevent overcharging.

To prevent overcharging above 13.8 - 14.5 volts.
Not to stop overcharging it beyond it's "full" state though.

The safe assumption is your car came with the proper charging alternator for
the amount of draw your car uses. Once you start changing things and start
putting too large of a "generator" in there, you can definitely overcharge the battery
if you're not pulling enough of the juice back off the system.

The regulator doesn't shut off til the engine shuts off, or it blows, or loses 12V signal.....
At least that is MY understanding, I could be wrong.

Think of electricity as water.

If a water pump (generator/alternator) has a regulator that is set to turn off at 14.4 PSI, and turns on at 12 PSI (14.4 volts/12 volts) and you're trying to fill a pressure tank (Battery), The flow (Gallons per minute/Amperes) would be high at the beginning because there would be little resistance. As the pressure tank began to fill, resistance would go up (ohms) and the GPM (Amperes) would begin to drop.

Once that pressure tank reaches 14.4 psi., the pump will switch off, which is basically what a voltage regulator does. It simply opens the circuit, which would be equivalent to pulling the suction line out of the lake, pond, river. etc. while the pump is running. Obviously a water pump can't do that. It will burn up, but you get the idea. ;)

The pressure tank won't get damaged unless the regulator on the water pump fails, allowing the pump to send more water pressure than the tank is rated for.

If there are 5 lawn sprinklers hooked to the same pressure tank, and each sprinkler will flow 25 gallons per minute (25 amps), you need a pump that will run at least 125 GPM. Let's say 150 GPM would be a good choice. There will be plenty of water to keep the pressure high (volts) and the pump could actually have a chance to switch off for a little while before the pressure (volts) goes down.

If you pick a pump that doesn't flow as much (let's say 100 GPM) it can't keep up. The pressure (volts) in the pressure tank will fall, the water pump will run continuously trying to keep up and, in turn, shorten its life.

I've never seen my voltage drop below 14.x volts on my Volt meter in my '70 442 with my 140amp CS130. even with all the accessories off, and no stereo on. So I'm just basing it on that.

That alternator is more then 2x the stock alternator amperage. (10DN ~63amp)

You could be right, but that's just my understanding.

Right. It's when all the accessories are on that you're going to see a voltage drop. Same as if all the sprinklers are on at once. You'll see a pressure drop in the system. That's why you see headlights dim when the bass hits on a lot of systems. It's equivalent to someone continuously turning one of the five sprinklers on and off, repeatedly.

I don't know what kind of a system you have, but in my '99 Olds, I have a Fosgate Punch 200ix DSM (much more than 200 watts) pushing two 10" P3's. The headlights dim at 70 mph on the highway. LOL

AAMOF, my Punch 100 DSM requires a 60 amp fuse when bridged into a 4 ohm load. Just outta curiosity I put an inductive pickup on the power wire right by the amp and saw 56 amps! Not too many alternators put out more than 30 amps at idle.

Anyway, I'm getting off track. To compare the pressure tank with a battery, imagine the pressure tank has a rubber diaphragm to separate the air from the water. The more often it moves, and the amount of travel it sees because of pressure changes, the sooner it will wear out. The more often a battery has been depleted and recharged, and the amount it has been depleted (voltage drop) the sooner it will "wear out".

An high output alternator (or high volume pump) will help reduce the amount the voltage drops (or pressure changes in the water).

Making a little more sense?

Keep in mind, I'm not an analogy specialist. This is roughly how it was explained to me in the classes I took at KCC.