Determining XO point from freq graph

[zenon]

Please follow the link:
http://www.partsexpress.com/projects...la/nebula.html

Note the graph "Software Modelled Frequency Response".
What I see is that the phase is reversed @ ~49Hz from the ported box tuning frequency. Then @ ~1.8kHz the phase reverses again @ the XO point. Is this correct?

I ask because it looks like the tweeter and woofer cross @ ~2.1kHz. But I'm thinking this may have something to do with the natural roll-off of the drivers themselves???

The reason I ask, is that I want to make this speaker except with an active XO. So naturally I want to know what XO frequency I should shoot for on my 24dB/octave Linkwitz-Riley XO.

TIA.

[RobWells]

When you use the 4th order LR xo, that will put your drivers phase 360 degrees out, so it's pretty normal to have some big phase differences at the xo point.

You need to pay attention to the baffle step compensation - most 'off the shelf' active xo's don't do this. You'd need to measure the boxes to find out what you need to do.



Looking at the bottom 'real' response graph I'd be worried about the big suckout in the 'kick' region - roughly 70Hz - 180Hz. Hopefully thats a room problem, otherwise these speakers would sound pretty weak.

Rob.

If your serious about doing the active xo check out Linkwitz' site for some great info:

http://www.linkwitzlab.com/

[soongsc]

It look like a very typical phase response.