Dayton ES180TiA inverted step response

[gparker]

Can anyone comment on why the Dayton ES180TiA step response is inverted? I am using Xsim and I have two different speakers hooked up, one is a Dayton DC200 (blue curve in the step response graph) and an ES180TiA (shown in red). I am using the FRD and ZMA files provided by the Parts Express website for both drivers. but for some reason the ES180TiA step response is inverted. Is there something I don't understand about step response, or is it possible something is amiss in the FRD or ZMA files for this driver?

 

[crossrh]

Put a capacitor on the tweeter and not a coil? I'm guessing here.
Or reverse the polarity of one of the drivers.

 

[gparker]

What I'm trying to figure out is, why does the step response show the ES180TiA driver as if it is connected out of phase. The other driver is another woofer (DC200) that I added just to see if its step response would be shown inverted, but it isn't. So I think Dayton may have generated the FRD and ZMA files with the ES180 hooked up out of phase. This leads to errors in xover design since the software thinks the driver is out of phase when it really isn't. I called Parts Express a few days ago about this and they tried Xsim with this driver and saw the same inverted step response with only this driver. They said they would get back to me, but I haven't heard from them yet.

 

[crossrh]

OK. I thought the DC200 was a tweeter. Nevermind about the cap.

 

[gparker]

Chris Roemer cleared this up for me so I will quote his explanation below...

"If you click on an FRD file (in Windows) it opens in WordPad, and you can see the 3 columns of data: Freq. (in Hz), SPL (in dB), and Phase (angle) - instead of showing phase running from 0* to 360*, it's shown (by convention - or .frd file specification) as -180* to +180*.

The ES180 (and the DC28) start off in negative territory (ES180):

19.86599 75.37 -11.1
20.19895 75.62 -12.9
20.53749 75.87 -14.7
20.8817 76.11 -16.5
21.23169 76.34 -18.3
21.58753 76.57 -20.1
21.94935 76.79 -21.8
22.31722 77.02 -23.4

The DC200 woofer starts out positive. That's the cause for all your concern.
I've designed hundreds of XOs w/out even looking at step response. I HAVE observed the "impulse response" when measuring FR in ARTA (you actually HAVE to look at the impulse to set your "gating" time). From time to time a batch of drivers will come out wired "backward" (at their terminals). The .frd file is still OK.

To make use of F/Z data (designing XOs) you have to either take mfr. F/Z files and "process" them, meaning creating "minimum phase" files AND using X, Y, and Z driver "offsets", OR ...
you can take your own FR measurements and use YOUR phase data (which includes "time-of-flight"), BUT - you can't change the position of your mic between driver runs or you lose the (proper) relative offset in your phase measurements.

You can NOT just use phase data out of mfr. data files (randomly). You have no idea the conditions (or distances) the data was collected at."

 

[Kakkadu]

I would do a polarity test on the driver. Maybe the terminal markings are backwards and the driver is reverse polarity in reality. Wouldn't be the first time it happens...

 

[gparker]

I did a polarity test on the driver. The terminal markings are not backwards.