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Old 6th January 2006, 09:10 AM   #1
audioa4 is offline audioa4  United States
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Default Passive Crossover questions

I understand the slope of a passive crossover is dependent on the impedance of the drivers in a loudspeaker. I ordered a 2-way crossover with a 3k hertz slope @8ohms. The problem is that the intended drivers are a 15inch 8-ohm woofer and a 16-ohm horn tweeter. I am unsure of the final crossover slope with this configuration. Any Ideas?


Here's the whole story:
I have some circa late 1980's 2 way 15inch PA cabs that recently had the crossovers cook/ the woofers fail. In a pinch I threw in some $30 4-ohm pyramid woofers I had, ripped out the internal crossover and ran the cabs bi-amped. with hopes to get the cabs back to simple operation I ordered some decent Pyle 8-ohm woofers and crossovers rated at 500 watts RMS and a 3k hertz slope @8ohms. None of these parts are in yet. I am not too sure if this combination will be desirable with the 16-ohm horn tweeter. What I really plan on doing is wiring up the jack plate,which originally had two parallel jacks, with a switch so I can still use bi-amping while playing live to calm my mind if the passive setup is wacky. I could replace the roughly 20 year old tweeter drivers to bring them up to 8-ohm spec if all else fails.

That said is there an online schematic for a 2 way passive crossover I can use 16 and 8-ohm drivers with that has a 2-3k slope?


yes lots of info/questions sorry, hope you can help
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Old 6th January 2006, 01:03 PM   #2
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A couple of options for dealing with the tweeter -

Since you're going to need to pad down the tweeter anyway, run a 16 ohm 20+W non inductive resistor in parallel with the tweeter - this will lose about 3dB, then you can work an 8 ohm L-pad to take care of the rest. This should work OK at home, where sound levels are sane. PA use might stress the resistor - bigger is better.

A better solution would be to rework the XO. My guess is that you'll get a second order filter if you just bought a generic 3KHz crossover. There are lots of crossover calculators on the web. This is the first one that Google found for me this morning http://www.ajdesigner.com/crossover/crossoversecond.php Among the L-pad calculators is http://www.lalena.com/audio/calculator/lpad/ I cannot vouch for the accuracy of either, but it really isn't that hard to calculate either.

If you really want the best sound quality, you'll measure your driver's response in their enclosures and design a crossover from scratch to suit.
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Old 7th January 2006, 04:29 PM   #3
carLito is offline carLito  United States
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Default passive crossover for a 15" black widow

i've got a 15" black widow hooked up to a 75-watt alpine amp in my vehicle, sounds great but the only problem is that the amp has no built in crossover and the vocals are loud as hell coming thru that black widow and i need to build a passive crossover that will hit a good range of bass - i have contemplated removing a crossover from an old 8-ohm home speaker box that also houses a 15" speaker - would i be better off doing that or should i just build my own? basically i just need the schematics for a passive crossover, any help would greatly be appreciated - thanks....
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Old 7th January 2006, 04:55 PM   #4
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I would never, ever, ever, use a passive crossover on a subwoofer.

Doesn't your alpine have a built in active x-over?

If not you can pick up a cheap active crossover designed for automotive use for under 50 bucks.
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