# Comments on my XO design so far



## Pancakes (Jan 16, 2008)

Sorry, typing one handed while holding a baby so this will be short-ish. For a whole bunch of reasons I'm looking at a 3 way second order XO for my new stereo speakers. If you have XO building experience please feel free to comment on the two variations posted below. My biggest concern is phasing right now. The XO is just so I can start using the speakers while I'm building an active crossover and multiple amps which will be a wee while due to the cost. I wanted to go 4th order initially but the component list would quickly get outta hand and as I want to use a ribbon tweeter and have the mid fairly broad band first order just won't cut it.

So, any comments or things I might not have thought of? Fire away. 

Thanks, Brian.


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## Bill Fitzmaurice (Jun 14, 2008)

Version A is standard. Version B has the merit of a 4th order characteristic for the tweeter, but since the impedance seen by the high pass section of the midrange section includes both the mid and the tweeter getting the calculations right is a much more involved proposition.


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## Pancakes (Jan 16, 2008)

Was planning to guess impedance then test to nail it down, I hadn't thought of the tweeter on the second diagram being 4th order but of course it is. So on A the phasing will be +90 deg on the tweeter, zero on the mid and -90 on the Woofer and B would be +180 (reverse polarity) on the tweeter, zero on the mid and -90 on the Woofer?

What else do I need to consider to sort out the phasing or is it going to be less of an issue with these pretty standard designs than I'm guessing it will be? I've done a bunch of other crossovers before but all the 3 and 4 ways have been 1st order, all the higher order xo's just two way. The components get big and very resistant (is that how you say that) up to a couple of Ohms, I want to keep the xo load under one Ohm and think I can do it by staying 2nd order.

To fill you in a bit more I'm looking at these speakers;

Tweeter; http://jaycar.co.nz/productView.asp...d2=&pageNumber=&priceMin=&priceMax=&SUBCATID=

Mid in 6L enclosure; http://jaycar.co.nz/productView.asp...d2=&pageNumber=&priceMin=&priceMax=&SUBCATID=

Woofer in 55L enclosure tuned to 24Hz, vents 80mm x ~400mm; http://jaycar.co.nz/productView.asp...d2=&pageNumber=&priceMin=&priceMax=&SUBCATID=

With the Woofer I trying to simulate a natural/sealed roll-off of Qtc ~0.6 above the tuning point.

the xo points will be ~2600 to 3k high and ~300Hz low. First step will be building the tweeter xo only as I'm not sure how much the resistance of that tweeter flucuates from nominal and can reverse engineer the xo once I see where it crosses in real world testing.

I have speakers for listening loud and want these to play the 300Hz to 3k range primarily through the mids and use the tweeter and woofer almost as a low super tweet and high-ish sub. Want good efficiency and low noise amps for very clean sound.


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## Bill Fitzmaurice (Jun 14, 2008)

Pancakes said:


> Was planning to guess impedance then test to nail it down, I hadn't thought of the tweeter on the second diagram being 4th order but of course it is. So on A the phasing will be +90 deg on the tweeter, zero on the mid and -90 on the Woofer and B would be +180 (reverse polarity) on the tweeter, zero on the mid and -90 on the Woofer?


Don't worry about the phase, as there are other factors involved that will affect it. When you wire the cab up test the mid with the woofer and try the polarity on the mid both ways, wiring it whichever way gives the better result. Then wire the tweeter and do the same.


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## Pancakes (Jan 16, 2008)

Bill Fitzmaurice said:


> Don't worry about the phase,


Awesome, that was by biggest hurdle and the thing most out of my control



Bill Fitzmaurice said:


> When you wire the cab up test the mid with the woofer and try the polarity on the mid both ways, wiring it whichever way gives the better result. Then wire the tweeter and do the same.


That was the back up plan to actually trying to figure out what the my result would be. As these will end up with an active fourth order xo this passive isn't going to make me lose sleep but I would like to listen to them while I build the amps.

Thanks for your input


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