I know that a capacitor in series with the pos. lead to the speaker will filter some lower freqs. , but how do you calculate the uF to pass it at a usefull high pass f like 80/100/120Hz....anyone know the formula..or just the value of the caps. used? radioshack sells the crossover capacitors,but naturally they don't have the values printed on them and they cost $15 a piece! I'd like to use the $00.50 capacitors since they are the same thing.

this particular sytem is a Pioneer DEH 3300 powering a pair of 6"s and apair of 6x9"s the RCA output is hooked up to a 350watt amp powering two sealed 12" Pioneer IMPP subs (bridged 2 ohms),the HU offers no low-pass cut off feature for the RCA output,but the amp has it's own LP cross over set to 80Hz. it sounds very good as it is,however it would have much more crankability once the lows are cut from the inside speakers. a four channel amp would accomplish this goal too,but there is really no need for an amp in there since it already sounds very clear,the subs do not interfere with the mids/highs at all,my friend has them turned down so that they only pick up where the inside speakers leave off.

 

4 ohm speakers:

...80Hz - 500uf
.100Hz - 400uf
.130Hz - 300uf
.200Hz - 200uf

Now you probably won't find the caps in those exact farad amounts. So you'll have to round up or down to get a rough estimate.

Thank the RF owners manual, not me.

AJ

 

BTW, the capacitors only drop the frequencies by 6db/octave, so it's better to go high on your cutoff freq, than too low.

AJ

 

here is the formula to figure it out

(1/(2(6.28)fXc))x1,000,000

f= the frequency
Xc= what kinda ohms the speakers are

that will give you you Uf that you need.

Later,

Josh

EDIT: aj is right about it only being a 6db rolloff too, so if you want say 300hz I'd go for about 375 or so. supposidly a octave is about 110hz. something ot think about

 

Just an FYI,

An octave is either twice as high (numerically) or half (numerically) than the freq. that is in question.

Example.

20Hz - 40Hz - 80Hz - 160Hz

Those are all one octave higher/lower than the other.

So 20K Hz is one octave higher than 10K Hz.

AJ

 

sounds good man, I dont' know much about octaves. :-) I'm used to hz is all, I've been reading up on em still don't know much bout em though LOL thanks for the clarification

 

No problemo, señor.

AJ

 

Just keep in mind that all of the crossover frequencies will be approximate at best, because a speaker's impedance is more complex than just "4 ohms". It will vary wildly with frequency, so you're going to be shooting at the hip unless you build a zobel impedance matching crossover - which you don't want to do.

 

Oh Jim. *slap slap slap your hand*

Don't go and confuse and scare the poor lads. Sometimes TMI is just gonna confuse peole.

Like me...... JK

AJ

 

that's what I always wondered!...where does 4ohms come from with a f range of 40Hz-20kHz?? a simple cheap inline cap. will probably get things working right in this car,we're just trying to keep the lows away from the 6x9"s that really can't handle them to well. hopefully,the mids and highs will improve as well.

Jim...I'd really like to build a "Zobel Impedence matching crossover" ! I can only guess what it does,but I'm interested in finding out how it works and maybee building one from scratch. what books can I find some Zobel info in?? will a single 400uF cap still effectively cut off frequencies below 100Hz for the time being?

 

well.....I still haven't developed my own ZIMX-over,but I did make it out to radioshack..which isn't my favorite electronics store but they did have a great selction of capacitors...470uF and 220uF I went with the 470uF because that would be somewhere around 85Hz HP. I hooked them up inline with the positive lead on both 6x9"s in this car. I thought it sounded a little better,they definitly didn't crap out as bad from bass either,the're not the best speakers anyway,they're some old alpine light duty papercone speakers,the pioneers in the front sound much better. I would like to talk my roommate into putting round speakers back there. I can't expect a single component to do the job of a real Xover network,but I think it still helps a little. I'd like to find some different uF values than 220 and 470 and wire them in with more of my installs unless they already have a crossover.

 

go to radioshack.com you can order different ufs off of there. they still don't have a ton, but more than any store I've been too.

 

ttt