Simulating crossover filters with REW PEQ's

[ebslo]

I'm trying to simulate some simple crossover filters by building them from the available PEQ filters. Some are easy, such as:

• 2nd order Butterworth is just an LP or HP (Q=0.707)
• 2nd order Linkewitz-Riley is LPQ or HPQ with Q=0.5
• 4rth order Linkewitz-Riley is two LP or HP (Q=0.707 each) filters at the same frequency

But I'm not having any luck finding how to build a 4rth order Butterworth. I presume (please correct if wrong) that functions theoretically exist: F1(f), F2(f), Q1(f), Q2(f) such that when 2 -LPQ or HPQ with (F1(f), Q1(f)) and (F2(f), Q2(f)) are cascaded they result in a 4th order Butterworth at f.

Does anybody know what these functions are (if they exist) or a reference to where I might find them? Or a better way to do this?

Thanks.

 

[John Mulcahy]

There is a table of 2nd order Q values in the help. REW also has crossover filter implementations in its Generic equaliser.

 

[kimmosto]

Few other types and orders, pages 46-56

 

[ebslo]

Thanks guys, that's exactly what I need. John, great documentation, all I had to do was RTFM! And kimmosto, that's a great reference with loads of extra good info.