# Passive crossover help



## HiloDB1 (Feb 25, 2011)

I recently got a set of 3-way 2nd order passive crossovers. I dont have any info on them besides what I can read off the crossover itself. I tried plugging in a bunch of different values in an online crossover calc but I cant seem to get them to mach up with this. It has an inductor of about 5.8mh and cap of 220uf on the low pass for the woofer. The bandpass has an inductor of 5.8mh and cap of 2200uf on the high pass and an inductor of about 0.13mh and cap of 10uf on the low pass. The tweeter has an inductor of about 0.13mh and cap pf 10uf for the high pass.

I would like to know what the actual crossover points should be at 8 and 4 ohms. Any help would be appreciated


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## ATOMICTECH62 (Jan 24, 2009)

Its almost impossible to figure out.
I have have tried it before and sometimes I can get close enough to figure it out plugging numbers in a calculator.But,the problem Ive found.You dont know if there using Bessel,Cheb ETC....Plus not all the drivers could have the same impedance.Some may even be odd like 6 ohm tweeters.
Also,if they are high end then they will be made with phase,odd slopes,targeted flat response ETC.....taken into consideration.
I tried doing it with an Infinity house speaker once and almost went insane.The component values were off by magnitudes when I finally found the published specs.


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## HiloDB1 (Feb 25, 2011)

Was thinking of trying to find it using a 4ohm resister and tone generator. Hook up the resister to each set of outputs and play tones around where I think the crossover frequency is. Measure voltage and see when it starts to drop off. Not sure if this would work and give me any indication.

I tried to just hook up a speaker on each set of outputs one at a time and play test tones and listened to when I notice it drop off but I got some weird results from that lol.

*edit - Found a formula online to calculate the electrical crossover points by using the inductor and capacitor values. These are the electrical values not the acoustical knee points. But using these I get some wonky numbers. 

With a 4 ohm load: 
Woofer low pass is 140hz with a Q of 0.779
Mid high pass is 140hz with a Q of 0.779
Mid low pass is 4415hz with a Q of 0.901
Tweeter high pass is 4415hz with a Q of 0.901

With an 8 ohm load the crossover points remain the same but the Q changes and gets a lot lower. This whole passive thing gives me a headache.


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