do i need to get a cap? im running 2 12" HE rockfords bridged on a 600 watt kenwood amp. and if so what size?

 

if your lights are dimming when you pound your bass, if your subs are unresponsive or if you feel you need one, then i'd suggest a 1farad cap. lightning audio makes good caps. rockford too.

however, some ppl say caps are useless and might even hurt your system. but i dunno about that. seems to be fine with me. someone just posted a car audio info site (and it's a good one) which also covers capacitors. it's in one of the previous threads...

 

One hawaiian is right on top of things, caps provide very brief shots of voltage if you hit a sudden demand, like a unexpected bass note. If you can hear the problem, a cap most likely won't be enough to fix it.
Most high frequency amp sets ups really don't get much out of them, caps are used mainly on bass amps like you have described.
The rule is one farad per thousand watts, so a 1 farad would be adaquate.
I run caps on all of the systems in the family cars, but allot of it has to do with the looks of them, and my stereo buying addiction!
If you have no problems yet, then no worries-

 

Blue LEDz is right about competition cars using them, I do judging, and it is something that can effect ratings. The 3Db number has been around for years, and I have seen it only occur in burbing contest, not everyday use.
Avoid the meters though, caps are rated by ESR, measure of resistance. built in meters wack ESR faster than anything.
He is also right on that 90+% are made by the same company. There are a couple of brands that require actual ESR testing prior to acceptance and require higher tolerences, phoenix and lightening audio. They are very much a commody item. Most solid state caps have terrible ESR ratings.

 

People seem to want to tiptoe around the subject for fear of getting sued- lets say this, alumapro and the direct desendents of it, are awful on the esr. For serious competition, build rack of three to six conventional winds, and you will get as good a results as you can. Truth is there is a level of diminishing returns with caps. Too much can effect alternator output as bad and not enough amps at the alternator. You are right on the numbers though, judges expect to see them is a car for points. Means youve spent more money on companies they deal with!!

 

Thanks Mon!!
I just got back from a nice dinner and drinks with my wife and daugher, and am headed to the sack! drop me a line anytime if I can help you in anyway-
dave

 

Thx guys for the info. So which brands should i be on a look out for? Also, i shouldnt get a meter on it? Oh and should i move my amp from the back of my box to like the back of my seat. How good is the kenwood amp? Sorry for all the questions. i dont know alot about this kinda stuff.

 

thx man! external monitor i like that. yeah i got my subs facing to the rear. so the vibration of the box will not shorten the life of the amp?

 

ok here is the thing i have 2 12"s in the back of my P5 and havea kenwood 600watt amp hooked up to them and i am only pushing maybe 3 or 400watts tot eh speakers i have on 1 frad cap hooked up to it as well and my headlights are still dimming with the bass. what do i do now i have all good wires everythign is 4 gauge wire

 

hmm, dunno what car/yr you have but it could be your alt was bad to begin with. check your electrical system b4 spending more money on anything else. sometimes the root of your problem (electrical) can't be avoided.

 

I posted in the other thread also, but I'll chime in here, to.

Caps will never help a bad electrical system. If the alternator cannot provide the power necessary or the amps, an extra battery and/or caps will do nothing - in fact, they will hurt the situation because they draw more power to charge, thus taking away from the amps.

Extra batteries are used for looks, and for engine-off listening. Mr. Cameron migh be able to comment more on this, but I believe that some, if not many, competitions require that the engine be off while playing the system for dB numbers. In this case, batteries and caps with the extra charge they store are useful. But with the car running, power for the amps comes from the alternator. An extra battery is an extra load. And a cap will help with one solid bass hit, but if the note continues past the point where the cap still has charge, you get dimming lights - and then the cap also has to re-charge, hurting the performance of the system during the charging of the cap (no matter how short the charge time is).

A cap might help with a "burp" - but for music listening, they do nothing for you while driving down the road.

And a cap giving an extra 3 dB??? Every 3 dB increase in SPL means DOUBLE the volume to the human ear. This is the way the dB system of measurement works. I seriously doubt that any daily driver system will be able to double it's volume with a cap.

 

Mr. Cameron? Who is this Mr. Cameron??
Dave- please!
Only clients and other barristers call me Mr. Cameron, and some of them call me much worse things!

There are several types of competition that requre the car off. I often try to suggest nicely to folks that they may not really want a competition car. Rules state they must make it under thier own power to the sound station, but afterthat it is no motor, or only limited rpm. The limited rpm is why many alternator specialist focus on saying at 2500 rpm the output is rated at___
There is not an alternator afloat that will produce maxium output at an idle.
So OK now you are up to using the battery only- but see what goes on in IASCA and Db Drag, the favorite vechiles of SPL these days are SUVs and Vans, becuase you have tons of room for Speakers and Boxes (The box of four 15s is huge if done right) and batteries in parallel to pump the amps for those breif few second of a meter test.
In a more regular car, a extra battery is of limited help, it will give you more time to listen with the engine off, but that is it, no extra power. If you do not use an isolator two will kill your alternator, it is twice the load. An isolator will flip one battery in and out of the system, but never have both tied in at once.
Caps have very limited use. They help you will small breif peaks of current demand, such as a cannon in the 1812 Overture, but that is it, they are fast charging, fast draining, little true storage. They will not make up for adaquate power from the alternator.
Hihoslva is right, a burp is too long a signal for a cap to make much difference, that is where the van full of batteries comes into competition these day.
Optimas are nice batteries, and I have used both yellow and red ones. Anymore for just starting purposes I use interstate batteries. The yellows will allow you to listen to the system until the battery is just about dead, and then take a near full recharge, that is it's speciality. No magic extra power, Cold Crank Amps is what to look for. The yellow just allows more full dead battery recharges. And then- be careful, and read closely the info on the Optima Site and the find a battery charger that will fit the recharge profile exactly. A yellow can do 300-500 recharges if done recharged exactly to specifications, but if not I have seen one wacked down to about 50 charges, I felt bad for the guy.
I have never met a magic 3 DB device, I would have them in everysystem I have ever put together if it exsisted. In burbing contest some folks claim that racks of caps attached to racks of batteries can make a difference, all I would say is that the last championship efforts I was involved with a couple of years back used batteries, not caps.