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Modifying 3 way passive crossover for 2 way electronic

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mtchyz250f

New Member
Modifying 3 way passive crossover for 2 way electronic

Several years ago I built a 3-way using some of my favorite speakers; JBL E145, Audax PR170M0 and JBL 2404. An Audio Engineer that way very familiar with these speakers designed a passive crossover and specified the size of the main cabinet as well as the cabinet for the Audax. Sounded great. We moved and my wife said those cabinets have to go. So I sold the old speakers (minus the E145s) to my brother in-law. So now I'm making new cabinets and want to experiment with a 2 way electronic crossovers (JBL E145 / Audax + JBL 2404). Unfortunately I can not contact that audio engineer to modify the passive crossover. Of course I could use an online calculator but the would not take into account the slopes he had to adjust for speaker performance in the specific enclosures (specifically for the Audax). I was hoping some one here could help me out.
 
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A second order crossover (which is what it says in the PDF) has a slope of 12dB/octave. But I'm a little unclear on what you're asking. By electronic crossover, do you mean an active crossover (i..e biamping)? Or are you referring to the standard passive crossover? If the former, you don't need a passive crossover at all (although you might want to put an appropriate capacitor in series with the tweeter to prevent accidentally sending any low frequencies to it). If the latter, you'll really need to start from scratch, since you'd be changing both the low pass frequency of the woofer and high pass frequency of the tweeter.
 
Sorry for the confusion.

I want to bi amp with an active crossover. One amp driving the E145 mid bass and another amp driving the Audax and JBL horn tweeter. So specifically, I am looking for the passive crossover between the Audax mid and JBL horn tweeter.
 
Get a dsp crossover and skip the passive altogether. This gives you a lot more flexibility in shaping the crossover curves and slopes.
 
C2 and L2 form the high pass for the midrange. If you want to experiment with the 500hz knee point or the slope with the active crossover, you'll need to remove those from the circuit.

Bypass the woofer circuit completely since you'll be using active filters to divide the woofer and mid.

Of course I could use an online calculator but the would not take into account the slopes he had to adjust for speaker performance in the specific enclosures (specifically for the Audax). I was hoping some one here could help me out.
Click to expand...

It looks like just a couple of Zobels added to a straightforward 2nd order network, you're going to bypass/omit the one on the woofer. As long as you put the Audax in the same volume and porting as originally used, the one on the mid should need no adjustment. It's there for impedance matching where the mid meets the tweeter.

Nice of the designer to include that schematic. :thumbsup:
 
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