Amp Question..

chromal · 07-05-2006, 02:32 AM

I just bought a 2004 Cavalier about a week or so ago and had my system installed "professionally".

I'm runnin 2 Audiobahn 10's (RMS 300 watts, Peak 600 watts)
Pioneer deck
1 Sony Xplode Mono 1000 watt
8 guage amp wire

Stock battery , stock alternator

The guy that installed everything said that the stock things in my car would for sure not have any problems whatsoever running the above mentioned.

After getting the car back though I do notice the lights dimming when sitting idle or driving rather slow. They dont dim the whole way through the bass, but I can definitely notice. Is there any way I can find out if there might in fact be a problem or if one would occur in the future? The car is practically brand new, only 14k miles on it and I'd like to keep it in good shape.

Thanks for any help.

parksgm · 07-05-2006, 02:49 AM

Quote: Originally Posted by chromal

I just bought a 2004 Cavalier about a week or so ago and had my system installed "professionally".

I'm runnin 2 Audiobahn 10's (RMS 300 watts, Peak 600 watts)
Pioneer deck
1 Sony Xplode Mono 1000 watt
8 guage amp wire

Stock battery , stock alternator

The guy that installed everything said that the stock things in my car would for sure not have any problems whatsoever running the above mentioned.

After getting the car back though I do notice the lights dimming when sitting idle or driving rather slow. They dont dim the whole way through the bass, but I can definitely notice. Is there any way I can find out if there might in fact be a problem or if one would occur in the future? The car is practically brand new, only 14k miles on it and I'd like to keep it in good shape.

Thanks for any help.

This question has been answered before, in detail, and recently. Do a search for "lights dimming" on the forums, and you should come up with something.

In short, the car's alternator produces less energy when idling or driving slowly because the engine is turning at a low RPM, which turns the alternator more slowly than when driving at faster speeds. Bass notes, on the other hand, take quite a bit of energy to reproduce, especially at loud volumes. So, at low engine speeds, your alternator is not producing as much energy as is being consumed by your amp, and the lights dim as a result.

For solutions, search for that other thread...

DJiK · 07-05-2006, 02:53 AM

A 1-farad capacitor should do the trick...

parksgm · 07-05-2006, 02:58 AM

Quote: Originally Posted by DJiK

A 1-farad capacitor should do the trick...

Yeah, or a amp with more internal capacitance. There's a recent thread that has a pic of the inside of a Sony Xplod amp...all transitors, and VERY few capcitors...which is likely fine as long as voltage or current in doesn't drop...I imagine that one reason that "nicer" amps perform better out of the box is that they have a much greater amount of built-in capacitance...

Shadow · 07-05-2006, 06:23 PM

Capacitors are a waste of freakin money and are useless in a car audio environment for any sort of voltage reinforcement. Voltage stabilization they do, but if your alternator can't handle your car's electrical draw, how is a cap going to help?
http://www.welcometotheden.8k.com/caraudio/Captest.pdf

First, you've got a very ineffecient amp.

Second, you're running a very small wire to the amp. Think of a garden hose vs a fire hose. The fire hose is way bigger than the garden hose so more water can get through. The same is true for fat wire. More room for more electron flow. Now, to produce power your amplifier needs two things: voltage and amperage. These are directly proportional to the amplifier's output wattage: voltage goes low, amperage goes high and vice versa. In your case, the current draw (amperage) exceeds what readily flows down the electrical hose so it drops your system voltage as it tries to gobble up more amperage.

Third, there's a REALLY good chance your gains are set wrong on the amp which will cause the amp to clip and have a huge current spike.

scott_fx · 07-05-2006, 06:27 PM

i completely agree with shadow and I'd also suggest upgrading the 'big 3' the garden hose analogy is also true with the ground and also how easy it is for the power to return to the ground (battery).

parksgm · 07-05-2006, 10:16 PM

Capacitors shouldn't be used to compensate for an otherwise underperforming charging system. If the charging system can't supply enough power to prevent battery discharge, adding what amounts to a faster reacting battery won't solve the problem because it simply stores energy without changing the rate it's replenished.

Unfortunately, capacitors are often wrongly recommended as a solution to an insufficient charging system (probably because they are cheaper than actually fixing the problem with a higher output alternator), but don't solve the problem, and so are seen as a waste of money.

However, in a situation where instantaneous current demand is higher than can be provided by a lead-acid battery (which is ultimately limited by the reaction rate of the chemicals that compose it), a capacitor is useful, and most definitely not worthless.

Or that's my two cents, anyway...

RedGTiVR6 · 07-06-2006, 11:54 AM

Quote: Originally Posted by parksgm

I imagine that one reason that "nicer" amps perform better out of the box is that they have a much greater amount of built-in capacitance...

B-I-N-G-O!

B-I-N-G-O!

B-I-N-G-O!

And BINGO was his name-o!

RedGTiVR6 · 07-06-2006, 11:56 AM

Quote: Originally Posted by parksgm

However, in a situation where instantaneous current demand is higher than can be provided by a lead-acid battery (which is ultimately limited by the reaction rate of the chemicals that compose it), a capacitor is useful, and most definitely not worthless.

In all honesty, this doesn't happen in a street driven audio system.

And I'm so happy that there are FINALLY people on this board that understand that caps are just a bunch of bandaids and not a real solution to the problem.

chromal · 07-06-2006, 02:13 PM

Quote: Originally Posted by Shadow

Capacitors are a waste of freakin money and are useless in a car audio environment for any sort of voltage reinforcement. Voltage stabilization they do, but if your alternator can't handle your car's electrical draw, how is a cap going to help?
http://www.welcometotheden.8k.com/caraudio/Captest.pdf

First, you've got a very ineffecient amp.

Second, you're running a very small wire to the amp. Think of a garden hose vs a fire hose. The fire hose is way bigger than the garden hose so more water can get through. The same is true for fat wire. More room for more electron flow. Now, to produce power your amplifier needs two things: voltage and amperage. These are directly proportional to the amplifier's output wattage: voltage goes low, amperage goes high and vice versa. In your case, the current draw (amperage) exceeds what readily flows down the electrical hose so it drops your system voltage as it tries to gobble up more amperage.

Third, there's a REALLY good chance your gains are set wrong on the amp which will cause the amp to clip and have a huge current spike.

Hmm... Well I called the guy back and asked him if I could bring it in and put a 4awg on it instead of the 8, and he replied that the amp couldnt hold a 4. So... I dunno. What should I set the gains to? They're both just right under halfway.

Would a yellow top Optima be a decent solution? I called the chevy dealer and they said if I were to put in a H/O Alt then it'd void my entire electrical system warranty and I really dont want that.

I'm stupid when it comes to fixing cars so unless Sound Advice/Best Buy/Circuit City knows about/how to do the Big 3 then that's not a solution.

RedGTiVR6 · 07-06-2006, 02:19 PM

Quote: Originally Posted by chromal

Hmm... Well I called the guy back and asked him if I could bring it in and put a 4awg on it instead of the 8, and he replied that the amp couldnt hold a 4.

If it can't accept a 4 gua wire then you must be running an adequate wire size to it.

Quote:

So... I dunno. What should I set the gains to? They're both just right under halfway.

There is no magical place you set the gains to.

Follow this how-to to properly set your gains:

http://www.350z-tech.com/zwiki/Tutor...plifier_Tuning

Quote:

Would a yellow top Optima be a decent solution? I called the chevy dealer and they said if I were to put in a H/O Alt then it'd void my entire electrical system warranty and I really dont want that.

Chances are, that by putting a PC in you've voided your electrical warranty anyways.

A bigger battery will only help if that is the problem. And it's not.

The problem is that you are running a low quality amplifier.

Quote:

Sound Advice/Best Buy/Circuit City knows about/how to do the Big 3 then that's not a solution.

I'd make sure that your ground wire is the proper size and then I would see if one of those places could upgrade your engine ground and the wires to the alternator.

The system you are running shouldn't need much more than that.

btw - if that amp only takes an 8 guage in, there's no way it's putting out 1000 watts...lol

Shadow · 07-06-2006, 05:00 PM

Yay, nobody fought with me about my caps are useless statement.

P = VR Power = Voltage * Current
1000w = 14.4V * X
X = 1000 / 14.4
X = 69.444 A

Assuming that amp is 100% efficient, it should have 3 25A fuses in the side. But that amp probably isn't even 50% efficient. Hence your problem

scott_fx · 07-06-2006, 05:08 PM

I've always wondered if voltage stabilization of a cap does improve SQ. Home audiophiles go to great lengths to get clean power to their components. Would a cleaner powersource yield a better sound in the car environment?

RedGTiVR6 · 07-06-2006, 05:13 PM

the SQ argument has been debated over the years, but honestly, being that I haven't seen caps in world championship cars recently...I have a hard time believing it.

scott_fx · 07-06-2006, 05:18 PM

hmm, that could be because the power supplies in the higher end amps handle all the voltage stabilization since the amps are purpose built with a messy (irregular) voltage supply in mind. Where as some of the lower end amps cut corners there, i wonder if a cap would help the lower end stuff