I have A kewood Amp which, Bridged at 2 ohms peaks at 500w and A 12" MD Sound Sub, the sub is 800w RMS and 1800w Peak with dual 2ohm voice coils all connected to a 1997 GMC Jimmy. My question is, do I need a capacitor? because when I turn up the volume the head lights, int. lights, and dash lights all dim with the music even while the vehicle is running. 
Thanks,
Thanks,
What would a capacitor do for this application and where would you put it?
The problem that you are experiencing is that your alternator likely isn't able to supply the power required to run your sound system and the rest of your car when you turn the volume up.
I would recommend purchasing a bigger alternator.. something around 130-140 amps.
Your amplifier is probably consuming around 42 amps of power assuming that it is drawing 600 watts at full load (since it is not 100% efficient). If your alternator is only producing 80 or 90 amps and the rest of your car requires 60-70 amps, you will be bumping up against the limits of your alternator.
To find the amperage drawn by your amplifier, divide total power in watts by voltage.
Finally, I would recommend getting a smaller sub woofer or upgrading your amp since it is not providing enough power to power thus sub. You should get an amp that can provide more than the RMS power specified by the sub. I have a smallish 8 inch subwoofer in my room that draws about 250 watts and it is plenty powerful for a 14x12 space so 800 watts is probably overkill imo.
The problem that you are experiencing is that your alternator likely isn't able to supply the power required to run your sound system and the rest of your car when you turn the volume up.
I would recommend purchasing a bigger alternator.. something around 130-140 amps.
Your amplifier is probably consuming around 42 amps of power assuming that it is drawing 600 watts at full load (since it is not 100% efficient). If your alternator is only producing 80 or 90 amps and the rest of your car requires 60-70 amps, you will be bumping up against the limits of your alternator.
To find the amperage drawn by your amplifier, divide total power in watts by voltage.
Finally, I would recommend getting a smaller sub woofer or upgrading your amp since it is not providing enough power to power thus sub. You should get an amp that can provide more than the RMS power specified by the sub. I have a smallish 8 inch subwoofer in my room that draws about 250 watts and it is plenty powerful for a 14x12 space so 800 watts is probably overkill imo.
I Don't know, I was told that a cap would store temporary power so the alternator would not need to produce as much and the amp would get an even amount of power and run more efficiently (or something to that extent).
Geez my factory alternator is rated for 130 amps. That’s not that much by today’s standards. Should be thinking more like 200 amps+ if you have problems like dimming lights. Keep in mind that full alternator output isn’t available at idle, but at around 6,000 RPM alternator shaft speed (around 2,000 RPM engine speed). That’s why you need one that’s rated for considerably more than what your total electrical load is.
Takes a big, expensive capacitor to do what you want. A higher powered alternator may cost less.
Before you put money in either, make sure the wires to your amp are super fat (like #6 or better), long thin wires at 12V can eat lots of juice that the amp never gets.
The speaker wires for a two ohm load, unless quite short, should be at least #10 or so to keep damping (punch factor) good.
The standard big car audio caps are pretty much useless. Their ESR is too high to be useful as a true capacitor, and they don't store enough energy to be useful as a power source.
Most of the energy store in the cap is never even used. A 1F cap charged to 14V is 98 Joules of stored energy, yet if your system voltage drops to say 12V under load, you are only ever using 2 Joules of that 98. See how pointless the cap is now?
Most of the energy store in the cap is never even used. A 1F cap charged to 14V is 98 Joules of stored energy, yet if your system voltage drops to say 12V under load, you are only ever using 2 Joules of that 98. See how pointless the cap is now?
I have a few thoughts
The amp bridged into 2 ohms puts out 500 watts...but you have a dual 2 ohm voice coil subwoofer? If you connect both voice coils together + to + and - to - that is a 1 ohm load. Your amp will attempt to drive that and suck amps as hard as it can to do it. If your voice coils are connected in series, that would be 4 ohms so your electric draw would be considerably less.
Bridging a "regular" amp into a 2 ohm load is a very inefficient way to drive a sub--it draws max amps and your efficiency goes way down as it generates a ton of wasteful heat. I would connect the sub this way to see if your pulsing lights go away.
Amp + to + on one voice coil
The - on the first voice coil to the + on the second voice coil
- on the second voice coil to the - on the bridged amp
That will give you 4 ohms and cut your electrical draw by at least 50 to 60%. If it does not dim anymore and you like the output--done!
If you feel the need to run 500 watts--get a digital amplifier for that function. They are much more efficient than Class A/B and won't eat the amps your electrical system can't provide. If you feel the need for more than 500 watts (because it sounds cool to say 1,000 watts) run a second sub to gain the +3dB which is the gain from 500 to 1,000 watts you would get running one sub.
It is not the watts, it is the output. Taught a friend of mine that and he blew the glass out of his car at "only 400 watts". The sub box weighed 325 pounds and was HUGE... but it sure was efficient!
The amp bridged into 2 ohms puts out 500 watts...but you have a dual 2 ohm voice coil subwoofer? If you connect both voice coils together + to + and - to - that is a 1 ohm load. Your amp will attempt to drive that and suck amps as hard as it can to do it. If your voice coils are connected in series, that would be 4 ohms so your electric draw would be considerably less.
Bridging a "regular" amp into a 2 ohm load is a very inefficient way to drive a sub--it draws max amps and your efficiency goes way down as it generates a ton of wasteful heat. I would connect the sub this way to see if your pulsing lights go away.
Amp + to + on one voice coil
The - on the first voice coil to the + on the second voice coil
- on the second voice coil to the - on the bridged amp
That will give you 4 ohms and cut your electrical draw by at least 50 to 60%. If it does not dim anymore and you like the output--done!
If you feel the need to run 500 watts--get a digital amplifier for that function. They are much more efficient than Class A/B and won't eat the amps your electrical system can't provide. If you feel the need for more than 500 watts (because it sounds cool to say 1,000 watts) run a second sub to gain the +3dB which is the gain from 500 to 1,000 watts you would get running one sub.
It is not the watts, it is the output. Taught a friend of mine that and he blew the glass out of his car at "only 400 watts". The sub box weighed 325 pounds and was HUGE... but it sure was efficient!
I would do a good battery first, the big 3, make sure you have good wire (4 gauge or thicker, i like 0 gauge then a dist block to all your amps) going to the amp, THEN do the alt if you don't have enough power. I think that just the alt. without the other stuff won't help much.
after all that, if you still have a dimming problem, step up to a larger class battery, or add a second one, again, with good thick wire and good grounding points.
knuzconceptz has great prices on all the installation stuff you need.
after all that, if you still have a dimming problem, step up to a larger class battery, or add a second one, again, with good thick wire and good grounding points.
knuzconceptz has great prices on all the installation stuff you need.
Good electrical wiring is a given, however you won't get anywhere unless you find out what your alternator is rated at. If it's only producing 90 amps, then no capacitor will solve your real issue. I believe that when you upgrade your car, it's important to do it correctly. Adding a second battery just masks the root problem... which is likely a weak alternator.
For safety sake I will try to find out what your alternator is rated at before you do something foolish. Electricity close to fuel in a closed environment is no joke. One spark could be disasterous.
For safety sake I will try to find out what your alternator is rated at before you do something foolish. Electricity close to fuel in a closed environment is no joke. One spark could be disasterous.
Update:
Your alternator is capable of supplying 105 amps MAX. It's not wonder that your lights are dimming... You will need a more powerful alternator if you want to supply enough electricity while running a 500 watt amplifier.
Remember that for most of the time your alternator will be generating less than 105 amps.
Here is what I recommend... Upgrade to an alternator that is 140 amps or greater, then make sure to use adequately thick electrical wires. I doubt that rewiring your subwoofer will change things dramatically unless you only use one channel (250 watts of power).
Good luck.
Your alternator is capable of supplying 105 amps MAX. It's not wonder that your lights are dimming... You will need a more powerful alternator if you want to supply enough electricity while running a 500 watt amplifier.
Remember that for most of the time your alternator will be generating less than 105 amps.
Here is what I recommend... Upgrade to an alternator that is 140 amps or greater, then make sure to use adequately thick electrical wires. I doubt that rewiring your subwoofer will change things dramatically unless you only use one channel (250 watts of power).
Good luck.
I'm guessing the dual 2 ohm voice coil is wired in parallel for a one ohm load The Class AB amp is bridged so each channel "sees" a half-ohm so the amp is running an impedance twice as low as it should. This will cause current flow to more than double as the amp attempts to produce 1,000 watts.
When he wires the two 2-ohm voice coils in series for 4 ohms...that should cut his power consumption at least 60% and solve the problem. If he upgrades his alternator or battery--it will provide enough juice to blow the output transistors on his amplifier much faster.
If you want maximum output without destroying your car's electrical system, run two subwoofers that are the most efficient available and use a digital "Class D" amplifier that are around 88 to 92% efficient. Class A/B amps are pigs--that is why they are so large, have huge heatsinks and generate a ton of heat. Figure efficiency of around 57% and it gets worse the lower the impedance it is driving. At very low impedance levels (under 2 ohms) they will convert half the power drawn into heat.
To get an idea--this would just be an example--battery voltage assumed to be 12.5V.
Class A/B (57%) at 4 ohms and 500 watts 70 amps
Class D at 4 ohms (92%) and 500 watts 43.5 amps
Class A/B (50%) at 1 ohm and 500 watts 80 amps
Class D at 1 ohm (88%) and 500 watts 45.5 amps
A car battery can provide "surge" current to make up for music peaks that are not constant. The larger your battery, the more current is available so voltage drop will be less but the alternator will have to keep it charged. Most vehicles can handle a Class D digital 300 to 500 watt monoblock amplifier as long as it has a decent battery/wiring and is not run to constant clipping.
The 300 to 500 watt recommendation only applies to car audio systems used for musical purposes--test tones and bass head hair trick stuff require alternator/battery upgrades etc. As I mentioned in a previous post, my buddy wanted more output with the same 400 watt amp--more woofers and a bigger box caused the glass to be blown out of his car. At least the electrical system didn't have any issues.
The Class AB amp is bridged so each channel "sees" a half-ohm so the amp is running an impedance twice as low as it should. This will cause current flow to more than double as the amp attempts to produce 1,000 watts. When he wires the two 2-ohm voice coils in series for 4 ohms...that should cut his power consumption at least 60% and solve the problem. If he upgrades his alternator or battery--it will provide enough juice to blow the output transistors on his amplifier much faster.
If you want maximum output without destroying your car's electrical system, run two subwoofers that are the most efficient available and use a digital "Class D" amplifier that are around 88 to 92% efficient. Class A/B amps are pigs--that is why they are so large, have huge heatsinks and generate a ton of heat. Figure efficiency of around 57% and it gets worse the lower the impedance it is driving. At very low impedance levels (under 2 ohms) they will convert half the power drawn into heat.
To get an idea--this would just be an example--battery voltage assumed to be 12.5V.
Class A/B (57%) at 4 ohms and 500 watts 70 amps
Class D at 4 ohms (92%) and 500 watts 43.5 amps
Class A/B (50%) at 1 ohm and 500 watts 80 amps
Class D at 1 ohm (88%) and 500 watts 45.5 amps
A car battery can provide "surge" current to make up for music peaks that are not constant. The larger your battery, the more current is available so voltage drop will be less but the alternator will have to keep it charged. Most vehicles can handle a Class D digital 300 to 500 watt monoblock amplifier as long as it has a decent battery/wiring and is not run to constant clipping.
The 300 to 500 watt recommendation only applies to car audio systems used for musical purposes--test tones and bass head hair trick stuff require alternator/battery upgrades etc. As I mentioned in a previous post, my buddy wanted more output with the same 400 watt amp--more woofers and a bigger box caused the glass to be blown out of his car. At least the electrical system didn't have any issues.
I don't recommend putting a car battery in your cabin because these batteries vent toxic fumes. You can purchase a sealed lead acid battery if you would like to put another in the trunk.
But another battery will act like a capacitor. It will just provide more capacity for spikes in energy usage. It will not fix the power supply issue.
If the alternator is rated at 100 amps, it will never supply those when idling.
If you have the engine idling in a parking lot, the amp only delivers very little power.
And in a regular car that is all okay, because it only has to feed the headlights and a couple watts for all the toys in the car like ECU and audio.
Modern cars, like say a Mercedes E-class (or anything similarly expensive), will turn comfort systems off when idling, just because the alternator can't produce the necessary juice.
(Ever wonder why heated seats don't get hot as fast when you turn on the engine, the headlights and all the other toys? Thats the EMS delaying the seats because you don't have enough juice available and other stuff like ECU is more important...)
Try revving the engine and see if the lights still go dim.
(And don't rev a cold engine. Also, don't rev it to the redline. Idle x 2 or idle x 3 should make a difference.)
And the first thing to replace would definitely be the battery.
It is a reasonably priced part that can be improved by buying a high-quality product.
Just check reviews for the battery size (physical dimensions) that your car can take.
What you are looking for is (obviously) a high peak current draw.
Aftermarket alternators are mostly **** because they don't match the rest of the car.
You end up charging the battery all the time (destroying it), increasing your fuel consumption (noticeably) and, if its a modern car, confusing the on-board energy management.
If the battery doesn't help, I would replace the amp and woofer next.
Because even a large and good cap (read: none of that stuff that is marketed to car hi-fi people) doesn't necessarily solve the problem.
A better, more efficient, amplifier should be able to do wonders.
The woofer would only be replaced in case its a particularly juice-sucking type.
And if all that doesn't help... then you may go ahead and use a good cap to help out.
If you have the engine idling in a parking lot, the amp only delivers very little power.
And in a regular car that is all okay, because it only has to feed the headlights and a couple watts for all the toys in the car like ECU and audio.
Modern cars, like say a Mercedes E-class (or anything similarly expensive), will turn comfort systems off when idling, just because the alternator can't produce the necessary juice.
(Ever wonder why heated seats don't get hot as fast when you turn on the engine, the headlights and all the other toys? Thats the EMS delaying the seats because you don't have enough juice available and other stuff like ECU is more important...)
Try revving the engine and see if the lights still go dim.
(And don't rev a cold engine. Also, don't rev it to the redline. Idle x 2 or idle x 3 should make a difference.)
And the first thing to replace would definitely be the battery.
It is a reasonably priced part that can be improved by buying a high-quality product.
Just check reviews for the battery size (physical dimensions) that your car can take.
What you are looking for is (obviously) a high peak current draw.
Aftermarket alternators are mostly **** because they don't match the rest of the car.
You end up charging the battery all the time (destroying it), increasing your fuel consumption (noticeably) and, if its a modern car, confusing the on-board energy management.
If the battery doesn't help, I would replace the amp and woofer next.
Because even a large and good cap (read: none of that stuff that is marketed to car hi-fi people) doesn't necessarily solve the problem.
A better, more efficient, amplifier should be able to do wonders.
The woofer would only be replaced in case its a particularly juice-sucking type.
And if all that doesn't help... then you may go ahead and use a good cap to help out.
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This is similar in my Buick. I have a 220 amp alternator. When I put it in park, the lights dim and brighten a little, but when I push the gas just a tiny bit.. the lights brighten and don't dim at all. But I've gone through several master mechanics. One says I need another battery, One says I need to wire my ground from the alternator to a better ground, preferably the battery ground. and the last one says that I have a bad alternator, although I've ran multiple tests and the voltage...and amps output is perfectly normal. The last opinion was that all my ground on my lights are bad....I haven't checked them yet, but I will have to do so very soon, for three of my light bulbs have blown out....lol...probably the voltage...bulbs can't handle it...or somewhat... Although I probably got scammed on the alternator.. I think it's a 160amp..and not a 220amp...considering the small size of the alternator...basically the same size of my stock, just a small pulley.
~About a capacitor, I've heard SO many bad things about them...they hurt your system more than they help...so it's more recommended for a Kinetic battery or something similar...Noted among...one that doesn't give off fumes lol.
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Having the alternator exchanged at a place that does not do a full "development" of it is an almost universally horrible idea.
Just popping a "larger" unit in a car can have all sorts of unwanted side effects, including (but not limited to ^^) slowly frying the battery, frying or causing unwanted operation of the regulator (unit that turns alternator-AC into on-board-DC) and frying and/or popping the fuses on all sorts of electrical neatness in the car, causing short lifespans in light-bulbs (!!!).
There ARE uses for stronger alternators. I am not doubting that.
But replacing it should be done at a place that knows its stuff and its NOT going to be cheap.
And if they tell you the regulator can be re-used, ask for the exact regulator-schematics and why it is supposed to be capable of handling the new alternator.
If they can't produce both at a minutes notice and explain to a noob most of the details: run!
Regards,
Jokener
Just popping a "larger" unit in a car can have all sorts of unwanted side effects, including (but not limited to ^^) slowly frying the battery, frying or causing unwanted operation of the regulator (unit that turns alternator-AC into on-board-DC) and frying and/or popping the fuses on all sorts of electrical neatness in the car, causing short lifespans in light-bulbs (!!!).
There ARE uses for stronger alternators. I am not doubting that.
But replacing it should be done at a place that knows its stuff and its NOT going to be cheap.
And if they tell you the regulator can be re-used, ask for the exact regulator-schematics and why it is supposed to be capable of handling the new alternator.
If they can't produce both at a minutes notice and explain to a noob most of the details: run!
Regards,
Jokener
I think messed up my calculations I think the amp actually does peak @ 1000w bridged to 2ohms can someone check for me, just to be sure. all the info on my amp at the link below.
Kenwood KAC-7204 (kac7204) 1000W 2-Channel Car Amplifier
Kenwood KAC-7204 (kac7204) 1000W 2-Channel Car Amplifier
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