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Old 22nd February 2003, 01:08 PM   #11
Bobken is offline Bobken  United Kingdom
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Quote:
Originally posted by mcyates
the sound does increase in pitch as i increase the engine revolutions.

The lights only dim when the bass is really loud.
OK. Then it could be worthwhile trying one of the massive caps you mentioned, as these act as a reservoir and release their charge at the appropriate time.

I must be honest and say that I believe your battery needs some attention though, in that it could either be underrated (for your higher requirements) or maybe it is not in such good shape.

Usually, the addition of a large cap like 1 Farad, will help with the firmness of bass transients, and it will marginally reduce the instantaneous current draw on the battery, but whether it will avoid the dimming lights situation, I have my doubts. The extra current available from the cap will be very shortlived, and possibly a better battery is the ultimate answer.

No cap like this will IMHO make any (much?) difference to the alternator noise, though.

If your battery is adequate for the much higher current requirements and it is in good condition, then it seems quite likely that you do have some impedance due to poor connections/earths etc.

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Old 22nd February 2003, 01:11 PM   #12
mcyates is offline mcyates  United Kingdom
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ok thanks alot for your advice. The battery is only 2 years old (same as car) but i've done 55,400 miles in 2 years.
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Old 22nd February 2003, 01:58 PM   #13
Bobken is offline Bobken  United Kingdom
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Quote:
Originally posted by mcyates
ok thanks alot for your advice. The battery is only 2 years old (same as car) but i've done 55,400 miles in 2 years.
Hi,

You are welcome, and I hope you resolve your problems.

It occurs to me to suggest that if you have a multimeter, you might check the various voltages in the car's system when the ICE is in use.

A good battery will measure up at about 13.6 volts (although they are nominaly 12volt) and if the voltage at the inputs of your equipment is much less than this, I guess this will be either due to the battery itself, or to the poor connections/earths etc.

When batteries are good and the alternator is working well, it is not unusual IME to see up to 14.5 ish volts when the engine is running at higher speeds than tickover.

It is certainly worth checking this out.

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Old 24th February 2003, 03:34 AM   #14
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Default More power, Mr. Scott!

The AC generator "output" lead is the big one shown in the photograph. The smaller wires are for the instrument cluster "battery" light and (depending upon the installation) a voltage sensing lead. Sometimes, a supplemental ground lead is installed on the generator chassis, in the case of a rubber mounted or floating mount.

The filter device (usually a capacitor) is installed on the BIG lead, and is best grounded at the generator chassis.

Most automotive electrical noise is reduced by grounding ("earthing", if you prefer) the radio head unit and amplifiers at the SAME point. This is commonly referred to as a "star" grounding. This reduces the minute voltage differences between the devices, the largest source being the rectified three-phase AC waveform from the generator.

Your amplifier thinks that this AC voltage is part of the audio signal, and it is dutifully amplifying it.

Other common sources of noise are the large electric motors in the car: the starter, the windshield wiper, the interior fans, and the radiator cooling fan. These sources of noise can be suppressed with individual capacitors.

A simple choke on the radio head power lead also works wonders.

Hope this helps!
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Old 24th February 2003, 04:01 AM   #15
PassFan is offline PassFan  United States
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Not sure if a capacitor will cure your dimming lights or not. Generally when the car is running the alternator supplies all current for operation as well as replacing what was used from the battery for startup. This is why on older cars you can disconnect the battery to check the alternator. Some of these boom, boom guys buy a higher output alternator. I know that police cars use higher output alternators because of the extra load from all the lights and radios and computers. How big are your amps. It's obvious the current demands are not being met when the bass hits and you can bet if your lights dim that your amps are distorting more as well. Good luck
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Old 24th February 2003, 04:47 AM   #16
usekgb is offline usekgb  United States
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Default BIG Capacitor

Those big 1 Fared Caps really do help with the power sags that big low end hits can cause. They work in the same way that reservoir caps work in power amplifier power supplies by providing short term power at full voltage. Adding these caps should eliminate your light dimming problem.
If you are really hitting the bass hard, you might want to consider installing a supplimental battery to your audio system. This will give you a much more availible current and will give your sub amp alot more power to work with.
If you really want to go over the edge, I have seen 2 Farad caps at PartsExpress. Just imagine linking a few of those together!!!!!!!

Hope this helps,
Zach
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Old 24th February 2003, 05:19 AM   #17
zardoz is offline zardoz  Canada
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Yes the big red wire is your output, clean the crud off the connection (use a bit of sand paper) and see if that helps. Check to see if there is meant to be a "bonding strap" from the allternator chasis to the engine block...then another from the engine block to the vehicle body. (I've seen broken straps and corroded connections make "noise" before). Then battery terminals get the same treatment..."clean and tight" no "grease" or anything else on the battery terminals.

Try the free stuff first

when faced with a high tech problem...allways look for a low tech sollution

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Old 12th March 2003, 02:34 AM   #18
CarMan is offline CarMan  United States
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Capacitor will NOT fix the dimming lights. It will make them dim less, but not much. The capacitor will help the amps out though, and an increase in sq may be heard, but will be very small unless you've got some crappy amps.

To fix this you need a NEW ALTERNATOR. Standard alternators put out 100amps. Dual alternators fix the problem completely, but I think a high power one usually fixes it unless you are really pushing the wattage (like 4000Watts +) I've got a 2 farad cap and a 1400wrms sub amp and a 400 wrms mid/tweet, and the lights dim almost to the point where i can't see them on the road. That's max volume, a little below and they dim much less. Max current draw ratings for my amps are 58amps and 37amps. That leaves 5 amps to power the rest of the vehicle. Mine personally hasn't, but I've heard of people's vehicles stalling when the bass hits. My engine rev's drop to ~400 rpm from 750 while idling if volume is max.

By the way, 90% of the time you can eliminate engine whine by running power/audio cables down separate sides of the car. Power cables and grounds should never be any closer to any audio wires than they have to. Also, many car audio wires are made that have shielding appropriate for this whine.
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Old 12th March 2003, 02:48 AM   #19
CarMan is offline CarMan  United States
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-Forgot to mention
There are somewhat cheap "ground loop noise isolators" if running power cables and audio cables separately doesn't fix the problem.

I don't know anything specific about how electricity works, but I know that *some* of the people who are electricly inclined never even THINK of the power/audio cable problem, and try some other stuff that doesn't work.
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Old 16th March 2003, 07:40 AM   #20
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Quote:
Originally posted by CarMan
Capacitor will NOT fix the dimming lights. It will make them dim less, but not much. The capacitor will help the amps out though, and an increase in sq may be heard, but will be very small unless you've got some crappy amps.

To fix this you need a NEW ALTERNATOR. Standard alternators put out 100amps. Dual alternators fix the problem completely, but I think a high power one usually fixes it unless you are really pushing the wattage (like 4000Watts +) I've got a 2 farad cap and a 1400wrms sub amp and a 400 wrms mid/tweet, and the lights dim almost to the point where i can't see them on the road. That's max volume, a little below and they dim much less. Max current draw ratings for my amps are 58amps and 37amps. That leaves 5 amps to power the rest of the vehicle. Mine personally hasn't, but I've heard of people's vehicles stalling when the bass hits. My engine rev's drop to ~400 rpm from 750 while idling if volume is max.

By the way, 90% of the time you can eliminate engine whine by running power/audio cables down separate sides of the car. Power cables and grounds should never be any closer to any audio wires than they have to. Also, many car audio wires are made that have shielding appropriate for this whine.


I really hate to step in the forums like this, but these kind of posts make people do / buy the wrong stuff for the wrong reasons. I am just coming over to the home audio community again after a long lapse to the car audio side.

Long story short... a capicator on the power line to help with bass notes is pointless. Typical voltage of a car when the car is running is around 13.7 volts. All the caps out there are 12 volt for cars. The cap won't begin discharging its energy until the voltage drops below 12 volts. Additionally, due to the ESR of the caps, the caps cannot release their energy fast enough to be of any use to the amp. If you already own a cap for a car, it will do much more good for you if you install it next to your headlights rather than in your trunk with the amps. If you want the doctoral math behind all of this, look at Richard Clark's forum:

http://www.carsound.com/ubb/ultimate...?ubb=forum;f=1

Additionally, unless you are running some seriously high powered amps for SPL competition, you do NOT need a second alternator. Most power loss (and thus the dimming light effect) is due to improper wiring. Depending on how far away your amps are from your battery, and how much current they draw, you'll need a certain gauge wire to accomodate. I'll post a link to a chart when I find it.

Also, star grounding is a wonderful technique internal to devices... not a good idea in a car. A car has a wonderful ground plane... the metal chassis of the car. All your equipment should be direct chassis grounded (you might need to scrape away paint to get at it), with as short a ground wire as possible. If two pieces of equipment (like 2 amps) are next to each other, using a single grounding point for them is recommended. However, grounding a head unit in the front of the car and an amp in the back of the car in the same place is not a good idea unless you have a ton of large gauge wire laying around. The car chassis is a much larger ground bus than any wire you could use.


Last, there are 3 "magic wires" as we refer to them in the car audio community. These are as follows:

1) alternator positive output to positive battery terminal
2) negative battery terminal to chassis
3) engine block to chassis

Those 3 wires should be swapped out (if they are already there) with the same gauge wire used from the positive battery terminal to your amps. That will solve about 95% of the light dimming problems out there. People run nice fat wire to the amp, but that last link from chassis to negative battery terminal stock is like 16 gauge... or the alt wire to positive battery is so small, that the juice is available at the alternator, but the wire is too small to accomodate the current you want from it.

Hope that helps...
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