View Full Version : farads?
12-01-2009, 12:54 AM
im running a 1300 watt mono-block amp for my 2 12 inch db drive subs and was wondering how many farads or what brand capacitor to get i have no idea on stuff like this and allthough i have had my setup for a while my radios starting to kind of dim with the music and everynow and then my radio will just turn off.the head unit im using for this is the kenwood kdc x492.i need help with buying the capacitor i dont wanna go cheap and have to pay double in the long run, thanks any help is greatly appreciated.
12-01-2009, 06:14 AM
12-01-2009, 06:30 AM
A general rule is 1 Farad for every 1000 watts. But I go extreme go 1 farad for every 500 watts. I would just purchase a 2-3 farad capictor so you have a little wiggle room.
12-01-2009, 06:52 AM
what do you think about the capacitors on ebay? they have some name brands for kinda cheap or should i just get one from a shop?
thats the one i id like to get mainly because my system is pure db but, what do you guys think?
12-02-2009, 02:39 AM
anybody?...what kind of wiring kit would be needed for the db drive capacitor? and would i be able to connect it myself or go to a professional?
12-02-2009, 04:25 AM
4 gauge IIRC
12-02-2009, 11:58 AM
would this wiring kit be good to connect the capacitor?
12-02-2009, 12:59 PM
IMO caps are useless. "they give more power when the subs hit"... surre but they are also charged by your stock charging system...They only really would help if your going to compete with "burps"... bumping your favorite song, its not going to do a damn thing for you. Upgrade your big 3 first, that makes more differance than any cap ever will.
12-02-2009, 01:01 PM
Ok I just wasn't sure and I hear people saying a capacitor will help my dimming and what not.and also cause my alternator goes out constantly
12-02-2009, 02:49 PM
if your running capacitors it will help your electrical system but will also lower db levels. if you don't care, then go for it.
12-03-2009, 10:48 PM
Large capacitors maintain supply voltage for a few 100 milliseconds when an amp draws peak current. They avoid the drop in supply voltage caused by V=I*R losses.
I = supply current, R = resistance of supply cable. If R = 0.04 ohm and peak supply current is 80 amps, I*R = 3.2 volts and the amp only sees ~13.8 - 3.2 = 10.6 Volts.
However, as the cap discharges the stored voltage drops as well, P = 0.5*C*V^2. A capacitor doesn't behave like an electrochemical storage battery and try to maintain a nearly constant voltage (minus the internal I*R losses.)
Obviously if you have a huge battery and alternator up front and large supply cable (double 0 gauge cables) you can mostly avoid the problem. However, using a small trcator or motorcycle battery to supply peak current combined with a 1 Farad cap will keep the supply at the amplifier at a nearly constant voltage.
The power cable running from the front to the back with then provide an almost constant current to recharge the battery between transient peak demands in current.
I'm not sure why car audio guys make this so complicated, I*R losses are well understood and the use of a small battery to provide loacl current to handle transients is well understood in many applications.
12-04-2009, 12:46 PM
Well said Jon. This is why any serious builds include several batteries.
And just so you guys know, there are only like 4-5 manufactures of large capacitors. They just change the decals or case on them to whatever car audio brand ordered them. So basically a cap is a cap. There truely is no difference between brands, performance wise.
12-04-2009, 03:58 PM
That's good information thanks, and my build isn't really serious I just wanted a little bump to my music.
12-04-2009, 04:55 PM
im using a 20 farad cap not that i have that much but plan on more so got it anyways but im in a totally different class lol
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