Please 'Boom' Responsibly As most of you have noticed, the noise ordinances have become much tougher lately. Most of this is due to idiots, yes IDIOTS, who drive through residential areas with their windows down while their system is playing at full power. To make things worse, the music they listen to has all sorts of foul language that's not suitable for small children, (who may be playing outside). There are even a few people, who are even beyond idiot status, that play their systems at full power through residential areas after 10:00 PM (when many people go to bed). I don't believe that this type of behavior is good for the industry. If the fines get too stiff, people will stop buying large systems. If this happens, more people will get out of car audio (who wants a mediocre system). People get interested in things because they're exciting. A deck and four 6.5" speakers are not going to interest many of the younger car audio enthusiasts. If car audio enthusiasts keep annoying more and more people, the fines will keep getting tougher. All of this will only reduce interest in the equipment that fuels the industry. If you want to listen to your system at full volume, get out on the highway where there's little chance of bothering anyone. When you get to a red light, turn it down. If the only thing attractive about you is your 'system', you have some work to do. Bottom line... Think about what you're doing. Think about other people. It's not the end of the world if you have to turn the volume down for a little while.

Capacitors in Series with Speakers:
Earlier we discussed passive crossovers. The simplest form of high pass crossover is achieved by simply putting a capacitor in series with a speaker. The proper capacitor is determined by the desired frequency response and the speaker's rated impedance. A more in-depth discussion of capacitor selection will be covered on the passive crossover page.

High Pass Crossover

Making the Connection:
For a 6dB/octave high pass crossover you simply connect the capacitor in series with one of the speaker connections (it doesn't matter whether it's the positive or the negative). There should be no positive or negative markings on the capacitor. If there are, you have a polarized capacitor and it will probably fail (which could cause the speaker to fail if the capacitor shorts when it fails). For best results, you should use a non-polarized or bi-polar (same thing) capacitor rated at 100 volts or more.
On the following graph, the green line shows how the signal level drops off (rolls off) as the frequency decreases. You can see the green line is virtually unaffected (there is virtually no decrease in the signal level) above ~2khz. At point A, you can see that the signal is down 3dB at 1khz. The 3dB down point is the crossover frequency (for Butterworth alignments). It represents the point where the power reaching the speaker is 1/2 of what it would be without the crossover. At point B, the signal level is down by 6dB. This represents the 1/4 power point. At point C (250hz), the signal is down by 12dB. This means that the amount of power reaching the speaker at 250hz is 1/16 as much as it would be without the capacitor.


You should remember:
1.When a properly selected cap is connected in series with a speaker, you can choose the frequency at which the low frequency starts to be reduced.

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