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Active Crossover vs Passive Crossover

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johneppen

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I am constructing a crossover with frequency of 100-200Hz, and it is for a subwoofer. First, i'm not sure what frequency works best. Secondly, if i understand crossovers correctly, an active crossover uses components like op amps and others. Where, on the other hand a passive crossover just uses inductance. My question is this, is the sound quality the same of both? Or are there substantial losses in quality in the passive crossover. Because, from my point of view the passive is much much, simpler to build.
 

Gene

New Member
For what it's worth, I built a passive crossover some time back that works very well. Here are my notes: The coil spool was made from two circular pieces of perfboard (4" in diameter each) fitted onto a 1 1/2" diameter wooden dowel. The top and bottom perfboard pieces were 1 1/2" apart. Onto this spool, I wound 150 feet of #18 AWG enameled wire - creating a 3.5 mh choke. I made two of these. The + side of my amp fed through one of the coils - the other end of the coil went to the - side of a 4 ohm woofer. The - side of the amp went to the + side of the woofer. The second coil is wired in parallel with the speaker terminals. (the reason the + and - seem reversed is to compensate for a phase shift) I have no way to test this set up except for my own sense of sound and by calculation. The result is a 250 Hz cut off to the 4 ohm speaker - Second Order Block - 12dB/octive. This does not result in a heavy boom but a smooth, realistic bass. If you are looking for the 1000 watt car application that will blow the trunk lid off your trunk (and probably render you deaf), this is not the circuit you are looking for. As to what is the proper frequency to tune your crossover, you should inspect the specification sheet for the speaker you are interested in buying and look at the top end of the response curve. That is, build the crossover to match the speaker.
 
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