Amplifier qualities & new alternators

Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=11365
Printed Date: July 22, 2025 at 8:11 AM

Topic: Amplifier qualities & new alternators

Posted By: Steve West
Subject: Amplifier qualities & new alternators
Date Posted: March 24, 2003 at 10:25 AM

Just wondering what are the qualities i should be looking for in an amplifier?

Ive heard about damping and SNR rates but have no idea what they mean or what they're measured in or whether i should be aiming for the high or low numbers!

Also, what should i look out for when in need of a better alternator? would the quality of sound decrease? reduced full volume?

cheers all

Replies:

Posted By: chucksnee
Date Posted: March 24, 2003 at 11:14 AM

What are you trying to do? Do you want to blow the windows out or do you want quaility sounding music? Or if you have enough money you can do both. Tell us what you willing to spend and the people on this board will do alot better to help you out.

There is a vast majority and varitity of amps out there.

Let us know and we will help.

Posted By: speedwayaudio1
Date Posted: March 24, 2003 at 12:53 PM

the higher the rms power the better the amp will sound also look for low thd .01 yes get a new alt. 200 amp at least. you can never have to much current only not enough. you could have a 1000 amp alt and it will not put that out unless it's needed by your system. get a 1000 amp battery too.

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Big Dave

Posted By: wrencher_25
Date Posted: March 24, 2003 at 2:08 PM

For the Amplifier - Like previously said, it all depends on what you want to spend. Also when looking for an amp check out the spec sheets. The lower the THD the better (as stated), also, look at what the max power is rated at.

For EG - 500W max power at 14.4V / Or it could be 450W max power at 12.66V.

According to Ohms law, Current is equal to Power/Voltage. The amp that's rated at 12.66V has a higher current output. They say that it's rated at 14.4V to make the overall power rating of the amp to look better. (Also note that 14.4V is usually the battery voltage when the car is RUNNING) (12.66V is when the car is not running).

As for your alternator, you wouldn't get lower voltage or decreased volume, but if you're running a big system, it's going to be harder for the ALT to keep up with the current that the amp drawing from the battery if the ALT ITSELF isn't putting out enough current. So what usually happens is the current gets drawn from elsewhere (That's why you'll see ppl with dimming headlights as the bass hits hard).

Hope that helped out a bit

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Andrew Weitzel

MECP First Class Installer

Posted By: donkason
Date Posted: March 24, 2003 at 8:25 PM

Unless you are looking to slam yourself stupid normally a second battery on a stock alternator would do a good job unless your stock alt. puts out a measley 70 amps or so. I have an optima yellow top and a stock 105 amp alt. set up on my car and it runs fine.

Posted By: Steve West
Date Posted: March 25, 2003 at 9:17 AM

I'll be looking to power a couple of RF Punch 401s's in da end. the specs on RF's site look like this:

S/N 100dB A-weighted

Damping Factor >200

Slew Rate 30 Volts/ms

IM Distortion <.05% <- huh? is that the same as THD?

P.S what kinda volume would i be looking for to kill a person?

Posted By: wrencher_25
Date Posted: March 25, 2003 at 12:33 PM

Did you look on an american website? I noticed that you're from the UK and their might be different names for specs. (Crazy British posted_image )

I havn't heard of a slew rate or an IM distorsion....but then again, I am new in this business and am learning more and more all the time.

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Andrew Weitzel

MECP First Class Installer

Posted By: thepencil
Date Posted: March 25, 2003 at 10:15 PM

Steve West,

Here is a link that you can take a look at when you are selecting your amp.

Damping Factor is the ratio of rated load impedance to the internal impedance of an amplifier. The higher the value, the more efficiently an amplifier can control unwanted movement of the speaker coil. A high damping factor is crucial for large speakers that reproduce bass. Usually the higher the number, the better, although it is debatable if anything over 50 is audible. Damping factor is calculated by dividing the load (speaker) impedance by the output impedance of the amplifier. Thus, a given amplifier’s damping factor will decrease as the speaker’s impedance decreases. This means an amp optimized at 4 ohms will provide tighter bass than at 2 ohms.

Before you go out and upgrade your alternator. You can actually do a bit of math to see if it is necessary to upgrade for one. First you have calculate the current draw from your amp. To calculate this you need to multiply the number of channels by the RMS watt per channel. If you have two amps you need to add both of them together to arrive at a grand total. Double it, then divide by 13.8, which is the average number of volts an alternator produces. The result is your system’s approximate current draw in amperes. For example, if you have a two channel amp that puts out 50 watt rms each. You would multiply (50 x 2)=100, 100+100=200, 200 divided by 13.8 = 14.49, 14.49 is the approximate current draw of your amp in ampere.

To calculate if your alternator can handle your current system or the system that you are planning to put in, you would then take your alternator amp rating and multiply by 40%. This will give you a rough idea of your electrical system’s reserve capacity. Say you have a Honda Civic that has an alternator rate at 50 amps, Multiply 50 x 0.4 = 20, 20 amps is what is left to power your sound system. I hope this sort of help you out.

This is just a rough guide, so change the number to refect what you have for your car.

Amplifiers: How to Choose

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Be careful whose advice you buy, but be patient with those who supply it. posted_image

Posted By: Steve West
Date Posted: March 26, 2003 at 10:30 AM

Cheers yall, thats really helped. posted_image

Yeah that was from the RF homepage, so i supose they might know enough to get there specs right...