Help a noob? Is crossover impedance on XSim accurate?

[Luke H]

Hi there,
Sorry if this is a repeat thread, I had a look and couldn't find an answer.


First time using Xsim to model some crossovers, my SPL is getting there but my Impedance graph is wild, way off what it was before I added any components.
Is this because I'm using stupid value components? Or wiring it incorrectly? An issue with Xsim or my data values? Or is just something I don't need to worry about?
Please could someone take a look at these screenshots and tell me what I'm doing wrong? Crossovers are doing my head in.



Any advise is greatly appreciated


Woofer: Dayton Audio DC160-8 6-1/2" Classic Woofer


Tweeter: Dayton Audio DC28F-8 1-1/8" Silk Dome Tweeter



Kind regards, Luke.

 

[AllenB]

Xsim is accurate if your data is as well. Try looking at the impedances separately to see whether they match the manufacturer's plots.

 

[Scottmoose]

It's currently 0322 as I type, and I'm on my old laptop so can't do any proper checking. However, leaving aside any comments on the merits or otherwise of the filter design itself, if by 'wild' you're referring to the large peak at about 1.8KHz, it's due to the electrical spread between the high and low pass crossover frequencies, i.e the nominal XO points are electrically speaking different, and a good way apart. This isn't 'wrong' -it is what it is. The larger the spread, the greater the peak. You can stamp on it with an LCR input Zobel. However, I'd say the filter needs more work anyway, assuming you've got measured on-baffle values for each driver, or at least well-simulated values accounting for diffraction effects etc.

 

[GeoffMillar]

Here's an interesting article which provides a revised crossover (compared to the Parts Express BR-1 kit) for your drivers:



MurphyBlaster Productions


I've tried to replicate both crossovers in Xsim using the Dayton supplied data and they don't look right compared to the measured FR and impedance graphs. Apart from anything else, my very basic understanding is that woofer impedance changes when installed in a cabinet.



Geoff

 

[Pano]

In most cabinets it doesn't change much at the crossover point, so rarely is it a problem.
As Scottmouse says, an underlapped or spread crossover will show peaks like that.

 

[Lojzek]

Luke,

as others have already concluded, XSim calculates impedance correctly and it is good that you question your sim findings. It would be even better if you searched for info on how to add, subtract, multiply and divide complex numbers and by using Ohm's Law you could manually calculate impedance yourself to check against any simulation software.

 

[Sonce]

Please could someone take a look at these screenshots and tell me what I'm doing wrong?

1. Too low corner frequency of high pass filter (too high C1), try C1=2.2 uF or 2.7uF. Or better yet, use second-order high-pass filter (C plus L).
2. Too big L1 value, try 2.2 mH or 1.5 mH. Or better yet, use second-order low-pass filter (L plus C), plus L-pad resistors.

Impedance graph is normal.

 

[Sonce]

Edit for my previous post above: L-pad resistors are for the tweeter (1.), of course.