BigBlue

Ok. I've been reading up on the Vette sites and some audio sites and most people say that caps are a waste of money. What's the deal with that? I'm tired of my lights dimming and my fuel pressure dancing around like some ricers neon lights connected to his subs. Any suggestions. I've got 2 audiobahn 12's with an audiobahn 1500w 1ch amp. 4 gauge wire is running it.

Jambbii

I wouldnt say caps are worthless. In my truck I am running a single 10 with 600 going to it and I am fine without one. In my challenger I am running 2 12s and I have an amp running my 6x9s and with crappy 1970s charging system I need all the help I can get. My buddy gave me a rockford cap and my lights dont dim anymore. Capacitors are made to store energy so the battery does not take a hit when there is a big draw.

Hope this helps

AlpineRAM

Some important facts about caps: They need to be very close to the amp, and wired properly. They need a shunt resistor for charging. They need to be big enough.
Most problems I saw with caps were from crappy wiring (eg small wire from the cap to the amp or bad contacts) and from using the caps without a shunt. (Kills alternators on vehicles with pcm regulated charging systems sometimes- and tends to blow fuses at the first charge of the cap)
I like to hardwire the cap to the amp with really fat cable and splice the charging (or B+) line into the cable with an 0,2Ohms shunt (will need to be a good one to stand the draw- like a 250W heat dissipation model)- This gives you a very nice and stable DC to the amp without noise and a rather consistant draw on the charging system.

AlpineRAM

SjLingenfelter

Tyler with you running an A1500HCT or HCX You NEED new batteries or a 2 farat CAP. When I was running that amp I had a 3.5 Farat CAP and we never had a problem. CAPS DO WORK. I have never had a problem with a CAP since I have been in Competition.

dodgeram

it used to be said that the reason to buy a cap was for better bass response, they don't really make a noticale diff so in that matter they are a waste


an optima yellow top has the same esr(equivilent series resistance) as a cap and therefore can supply the power as quickley as a cap on those bass transients, therefore it will give you all the benifits of a cap(stop the dimming lights) and it's a darn good battery to boot

excide's orbital XCD is also a low esr battery

I'd buy a set of either one of those before I bought a cap (this is coming from a guy who wasted money on 3 1 farad caps in the past, they are a bandaid for dimming lights though, they do cure that)


also be sure to upgrade the "big 3" too

big 3 = battery to frame ground, alt to frame ground, amp ground (they all need to be at least the same size as your main amp power feed and it should be at least 2 guage with the power you are running)

BigBlue

Well, it really doesn't make any difference now, the freaking subs blew. This is my second set in a year. I'm either upgrading subs (to either a higher wattage or JL W7's) or getting rid of them period. I love my bass but I'm tired of this crap. Maybe just buy one of those wal-mart sets where the amp and sub come as a package.

DODGE4X4

I've got a Rockford cap and the instructions didn't say anything about a shunt. What exactly does a shunt do and what is it? I have the cap hard wired into the Rockford amp with big cable and I followed the instructions to a T so I don't think I've done any thing wrong in that regard... So do I need a Shunt??

SjLingenfelter

With the Power he is running 4ga will be fine and has been fine for 1 1/2 now. Ive got the system set up the way it should be and the only reason I thin k the subs are blwing is because of the power surge running from the amp. Cause it doesnt have a CAP on it.

AlpineRAM

How many connectord does the rockford cap have ? (I've seen some "caps" being sold over here that actually were a cap and a shunt in one case assembly- you could tell by them having one wire labeled "batt" or "charge" and another "amp" and one or 2 ground connectors )

A shunt is a resistor that will reduce the draw on the vehicle's charging system by limiting the current the cap draws to recharge. Effectively this will lower the supply voltage to the amp a little under heavy draw, but the voltage will stay stable.
Other folks have good results with an optima battery connected to the amp directly. (Short cables good )

AlpineRAM

Eskimo

Keep your ear open for distortion, and you won't blow up your subs anymore.

As for the size of the cabling, dodgeram is right. Let's use a little bit of Ohm's law. If that amp (I don't trust Audiobahn, but let's assume) is really 1500 watts RMS, then at 12v, and 100% efficiency, it's drawing 125amps of current. 4 gauge is rated at 150amps continuous for SHORT runs of around 4-5 feet or less. considering the ~15 foot run you probably have, then you're getting voltage drop in the wire already.

But wait, there's more! I mentioned the amp being 100% efficient. it's not. Far from it in fact. Class AB amps are typically about 50% efficient, the other 50% turns into heat. Class D's are more efficient, but still are in the 60-70% range. so.... now you're up to 250amps of draw! 2 gauge wire on a 15' run could support this with minimal voltage drop.

"But Eskimo, my fuse is only 100amps, and it never blows".. Well, you're not using full RMS power all the time. Also, the manufacturer has probably overstated the rating on the amp. BUT... When a momentary large spike goes through the amp (a hard kick drum for example), you can pull ~200% of the fuse's capacity without it blowing. They're not an instant-acting device. But, your 4-gauge wire can't support that kind of current draw, so voltage falls, which increase amperage pull, and reduces the amount of power left for the rest of the truck... Hence your disco lights.

I haven't been into competition audio in a couple of years, but there are certain things that don't change.

upgrade your batteries, or get a 1-2 farad cap, and wire it CLOSE to the amp. It WILL help.

Dufrain

How about upgrading the charging wire from the alternator to the batteries to 4 guage or so also.There are some alternator upgrades on ebay for some good prices to.
I am running a concept ccd-2400 in my van with 4 guage that was already in there,i plan to upgrade.It has the stock charging system and one battery and it does dim the lights but I have never blown a sub and its been on there for 3 or 4 years.It has more than enough bass to fill the huge astro van interior with bass.
I have talked to the amp companies and alot of the guys on the audio competition forums and most say a cap is a band aid because your alternator and batteries still have to fill up or charge those big capacitors and if more is going out of them than going in they dont do much.Most good sub amps have a cap bank built in.its just a bunch of small ones inside.But not as much capacity as the external ones.

I think if you follow the above advice and upgrade all your wiring and maybe install some new optimas and maybe a 3rd close to the amp if you have room.If you still have trouble upgrade the alternator.

BigBlue

Eskimo, my amp is 1500w peak, not RMS. And it's not even turned up all the way. The volume was only at 80% of what I usually play it at and the subs weren't distorting. I think I'm gonna go and buy some 0 gauge wire and run that into a distribution block and run 4 gauge from there. I think I'm also go run all of power wires under the cab and the RCA's inside the cab and remount the amp on the back wall behind the seat.

SjLingenfelter

Tyler Dont mount wires under the cab just get some 2ga wire and be done with it. Aut gauge is gonna run you a pretty penny. Anfd when you rerun it. Dont run it into a dist. block run it strait from batt to amp. When you drop the subs off to me I will explain everything for you to do.

Dufrain

better put a main fuse by the battery,if you rub that insulation off the amp wire and no fuse youll burn your truck down.

FastSS

Optima batts are basically a bunch of caps wired together from what I can tell, I run a 1 farad cap on my Impala and ran a 1 farad on my Integra for quite a while, it did the job quite well

On the fuel pressure gauge, they do that... thats just the nature of our trucks... mine dances +-1-2 psi

eskimo has a good write up

I was pushing ~ 800watts in my integra with 4ga wire with as short as the wire needs to be to run to the cab of our trucks I dont think 0ga wire is needed

I do not agree with alpine ram, I believe that the resistor defeats the point of the cap... however a resistor is REQUIRED for initial charging although I never used one and worked out ok, I just did a couple of "taps" with the doors open... the resistance of the light bulbs kept my inital shock down enough that I was ok... and I am talking a totally wired cap with the negative terminals off of the batts doing the "tap test"

Stupid? yes.

1 farad is a LOT of energy, and it needs to be treated with respect... when charged that cap should have enough energy to give you serious burns if not turn entire apendeges into the microwave hotdog effect...