What do capacitors do?

I know that capacitors store electricity, but never knew why they were used in stereo's. Is it because you get better bass because you've got that extra power there waiting to use? Do they really make much difference?

What size capacitors are you talking about?

You usually put huge capacitors (1 or 2 F) to stop voltage drops in your system. A capacitor is able to expel all it’s energy/electrical charge in a split second. A double A battery can actually hold more energy than a 1 F capacitor but is useless for stopping voltage drops because it can’t release all that stored energy when it’s needed. They have what’s know as a Thevenin resistance.

You can also put capacitors either in series or parallel to filter out the low and high frequencies respectively. I think a 220 micro F cap in series with a speaker filters out low frequency.

Awesome, thanks for ya help

Think of a capacitor as a spring (infact their energy equations are the same). If a cap sees a drop in voltage it tries to compensate by delivering current. So the practical aspect of this is a big bass note needs a heap of current, drops the voltage on the power cable due to resistance in the wires, capacitor does not like this so it supplies current to boost the voltage. If you are asking about the 1F caps, mount them as close as possible to your amp.

ps. Don't waste your money on gold contacts.

Mike

Exactly right dephilile. Interesting explanation there too Michael! (never heard that "spring" thing before, but very logical!)

Capacitors impede the flow of low frequency energy, by virtue of what is called "capacitive reactance". As the frequency increases, the reactance decreases. Inductors (coils) do the same sort of thing, but in reverse - frequency up, reactance up. For that reason, the most basic type of speaker crossover is simply a capacitor in series circuit with the tweeter - thereby only allowing the higher frequencies through. (higher end crossovers will use inductors as well)

However, 220uF (micro-Farad) is far too large to use - you'd destroy your tweeters in seconds if you were to use a cap of this value. Generally for 4 ohm speakers, the series cap for the tweeter should be somewhere between 4.7 and 10uF, depending on where in the frequency range you want the tweeter to become active. (smaller capacitor, higher crossover frequency) For a 220uF capacitor the crossover frequency would be about 180Hz - I don't know of a tweeter in this galaxy that will enjoy a frequency that low, unless it happens to be a "piezo" type tweeter. Piezo's appear (to the amp driving them) as a capacitor, and in fact can be used without a crossover network at all, the device simply won't even try to produce low frequency energy. (but I'd never use a piezo except in PA type scenarios. They're tough, but the sound is a bit harsh and "tizzy")

Anyway - I'm doin' it again - writing a bloody book!!

Cheerz!

Also, another use for capacitors that I stumbled across. In main power supplies cables for amps, dropping a capacitor can quite often remove alternator whine It won't remove an earth loop, but engine noise can easily disappear. I didn't believe it until I thought about the way a Cap works then it made perfect sense!!!

Great trick Trunk!

Does make perfect sense.

OOPS! :embarrass My apologies Dephilile....

Read your reply to another thread Trunk, you described using a 220uF cap for high-pass on front speakers - exactly what Deph is talking about.

My reference to the 220uF was specifically when used with TWEETERS. Not having a sub in my system sometimes I forget the little things :b: - yes, a 220uF is perfect for the HPF to 4 ohm door speakers, rolling off the response below about 125-150 Hz. The LPF on the sub amp is set to about the same, and the drive adjusted to balance the system.

I stand humbly corrected.

No problem

Yeah, I used to have a 220micro F cap on my 6x9’s in the back because I have a 12” sub. I removed it after I realized my head unit could remove those low frequencies for me. Why did I get 6x9’s if I was only gonna filter out the bass? They were in my old car in which I didn’t have a sub.

dephilile said:

Why did I get 6x9’s if I was only gonna filter out the bass?

Click to expand...

You know, I asked myself the same question as I put four 10" subs into my old wagon...