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Could someone answer questions about putting together 2 way high pass crossover?

#3
My initial questions are for a 2 way high pass crossover, how do I match the inductor and capacitor? I'm looking to crossover at 3.9 /4 khz, are they both set at that frequency? Looking for a 2nd order bypass. What gauge wire should I be using? Would it be much better to also wire up a low pass filter for my woofers?

From the wiring schematics I've seen, it looks like the capacitor is in the chain before the tweeter and the inductor is before the woofer? Where does the attenuator go in the chain?
 
#8
BassMan5k said:
See this is why I could use an actual person to help out. I've looked at a bunch of these, so I'm guessing the high pass only lets above that frequency and the 2nd order is the 12 db curve?
Click to expand...

Correct. A "second order highpass" filter theoretically rolls off that driver's response at 12 dB per octave below the filter's frequency.

I always make my own suite of measurements and figure out my own "target curve". I never end up using textbook crossover filter values and almost never use textbook filter topologies. The specifics always matter, and even with perfectly reliable published curves, you still don't have enough information (for instance, what is happening in the phase domain, and how does inter-driver offset affect it?). And by far most of the components in my crossovers are dedicated to shaping the frequency response rather than performing the actual function of "crossing over". So I never try to armchair-quarterback crossover designs.

Okay that being said, what I do is totally impractical for most people, but I wanted to let you know that it's not so simple out in the real world. Without knowing the specifics about what you're trying to do, and assuming you're limited to spec sheets and online calculators, here is what I suggest:

1. Make your best guess as to the impedance of the driver in the crossover region. If it's an "8 ohm" driver and when you eyeball the curve it looks like 5.5 ohms in the crossover region, then use 5.5 ohms.

2. Plug that impedance and the desired -3 dB frequency into an online calculator (staying within the manufacturer's recommendations for frequency). If given the choice, use the "Butterworth" type filter - it's more forgiving than most. The program will give you capacitor and inductor values.

3. Build the filter and try it with the high-passed driver in NORMAL polarity (same polarity as the woofer), and also in REVERSE polarity (opposite polarity from the woofer). Without knowing what's going on in the phase domain for BOTH drivers, plus the voice coil offsets, we can't reliably predict in advance which polarity will work best. The one that's loudest through the crossover region is the "correct" polarity, but it's okay to use whichever sounds best.

Hopefully the net result will be just what you wanted, but I make no guarantees.
 
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#10
Thanks so much! Tried using a calculator, didn't realize that the capacitor and inducer would be different values from 4khz, that's definitely helpful.

I'll get my cab (just had a gig and at band practice house) soon to check on everything, I just feel like I have general idea on how to put the thing together and the audio guides online aren't helping me internalize the knowledge and really understand. Just need a teacher or someone to discuss.

DukeLeJeune said:
Correct. A "second order highpass" filter theoretically rolls off that driver's response at 12 dB per octave below the filter's frequency.

I always make my own suite of measurements and figure out my own "target curve". I never end up using textbook crossover filter values and almost never use textbook filter topologies. The specifics always matter, and even with perfectly reliable published curves, you still don't have enough information (for instance, what is happening in the phase domain, and how does inter-driver offset affect it?). And by far most of the components in my crossovers are dedicated to shaping the frequency response rather than performing the actual function of "crossing over". So I never try to armchair-quarterback crossover designs.

Okay that being said, what I do is totally impractical for most people, but I wanted to let you know that it's not so simple out in the real world. Without knowing the specifics about what you're trying to do, and assuming you're limited to spec sheets and online calculators, here is what I suggest:

1. Make your best guess as to the impedance of the driver in the crossover region. If it's an "8 ohm" driver and when you eyeball the curve it looks like 5.5 ohms in the crossover region, then use 5.5 ohms.

2. Plug that impedance and the desired -3 dB frequency into an online calculator (staying within the manufacturer's recommendations for frequency). If given the choice, use the "Butterworth" type filter - it's more forgiving than most. The program will give you capacitor and inductor values.

3. Build the filter and try it with the high-passed driver in NORMAL polarity (same polarity as the woofer), and also in REVERSE polarity (opposite polarity from the woofer). Without knowing what's going on in the phase domain for BOTH drivers, plus the voice coil offsets, we can't reliably predict in advance which polarity will work best. The one that's loudest through the crossover region is the "correct" polarity, but it's okay to use whichever sounds best.

Hopefully the net result will be just what you had hoped, but I make no guarantees.
Click to expand...
 

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