David Giesbrecht

Phase shift

how come I keep hearing about 2nd order crossovers having a phase shift? do they actually reverse the phase of the speakers in the network?

RichardHOS

Yep.

Patrick Sun

Theoretically/simplistically speaking, each "order" of a crossover filter introduces a 90 degree phase shift at the crossover point. So with a 2nd order crossover network, you've got an 180 degrees phase shift that gets corrected by flipping the polarity of one of the drivers (for a 2-way), otherwise, you'd experience a null at the crossover point.

"I am a leaf on the wind, watch how I soar!"
Patcave | 2006 Films | 2007 Films | Dragon Con 2007

David Giesbrecht

Does a first order network put a 90 degree phase flip on the driver? I heard that first order networks didn't effect phase and that was one of their advantages.

RichardHOS

I was going to ask the same thing.

I know I've read it before, but now I have myself thoroughly confused.

a 24dB/oct has a 360 degree phase shift. A 12 dB/oct has a 180 degree phase shift. That would seem to suggest 6dB/oct = 90 deg and 18dB/oct = 270 deg. But I was almost certain that a 6dB/oct filter didn't have a phase shift.

Someone (hopefully someone smarter than I) please help!

Hailan R

Patrick Sun

First order XO networks are more like minimum phase networks.

You have to think of phase as "delay", and the magic of complex math applies. Gives me a headache.

Here's where you can download an article on the topic:

http://www.geocities.com/kreskovs/Phase-B.html

And another article on the terms from the same author:

http://www.geocities.com/kreskovs/TimeAligned1.html

"I am a leaf on the wind, watch how I soar!"
Patcave | 2006 Films | 2007 Films | Dragon Con 2007