# Setting up a active crossover



## duder1982 (Aug 28, 2012)

Ok the basics of this seems really simple, but then there are the options to possibly make fine tune everything, this is my reason for trying an active crossover. I really don't want a discussion on which is better active, or passive, I feel that is each to his or her own. How ever I am currently working on setting up a active cross over and want to fine tune it. Does anybody have any good reading info out there to read that might help me understand, tutorials are all so nice as i am sometime need to see how things work rather then just reading how they work. I know I can go in and set the crossover, and even some delay based off of simple measurements and calculations. But what if I want to eq this speaker, what are the steps for that. I am trying to better understand this process and at times I feel I looking for the wrong answers or asking the wrong questions. This is so far my perspective of this whole idea.

1 Time align or adjust phasing.
2 eq each driver (can I use REW's auto eq function for this)
3 Set crossover

Now I know there are different ways to go about this such as

If I eq first then set time alignment I may need to go back and eq again but do I eq the speaker as a whole or each individual driver. These are the things that get confusing, last if auto eq wouldn't work, how to you know what to set for your PEQ settings, how does one go about equing the dips and peaks to give you that flatter line.


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## fusseli (May 1, 2007)

I would set the delays first, that should help each get in phase with each other so your EQ and crossovers will add properly.


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## wrswrsnz (Oct 5, 2012)

Which active crossover are you using?

If the XO introduces frequency dependant phase shift in the stop-band at each crossover point it may not be any better than passive XO from a phasing perspective. Sure, you'll get better amp/speaker coupling if the passive XO's are removed.
eg, If the XO uses low-pass and high pass IIR filters it will have different phasing in the stop band. If it uses delay compensated FIR there will be no phase error, just delay. If it uses LPF and APF then subtracts the LPF from the APF output you will get HPF with the same frequency dependent phase delay as the LPF - best compromise if using IIR.

A properly design XO will have matched or no phase shift at the crossover points so both drivers exhibit the same phase in their stop-band. This will make the speaker sound more open and improve the benefits of going active.


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## wrswrsnz (Oct 5, 2012)

As above, set delays and use white noise to check phase / time alignment.
The set levels using REW - get everything as close to the same level as possible.
Then do the correction.

Target is to have the correction do as little as possible to maximise resolution.


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## duder1982 (Aug 28, 2012)

Mini dsp 2x4.

One question I have, what causes phase shift at the crossover point.

One thing I do need to get proper measurement tools for setting delay. I have read its not really possible with umik-1.


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## natehansen66 (Feb 20, 2011)

duder1982 said:


> One thing I do need to get proper measurement tools for setting delay. I have read its not really possible with umik-1.


In REW you need a separate mic and preamp to do this. The best you can do with what you've got is to use an in-phase xo topology such as an lr24, flip the phase on one of the drivers, and adjust the corner freq and delay until you get the deepest null. Which driver to delay will depend on your speaker. A typical cone and dome bookshelf might need delay on the tweeter as the low pass on the woofer will delay the woofer. It depends......

Or.....you can use Holm Impulse with your Umik which can remove the latency from the measurements and you'll be able to see the relative phase for each drive unit when done correctly.


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