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Feedback Request: 2-way passive design
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Old 15th July 2017, 05:22 PM   #11
bungelow_ed is offline bungelow_ed  United States
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Quote:
Originally Posted by Lojzek View Post
Try to compare these with your own.
Lojzek, You've given me much to think about. Starting with a look at the woofer graphs, side by side, in XSim. Our impedance peaks are different, with mine higher. My graph has a narrower gap between peaks, though the lowest point is at the same frequency.

The noted difference lead me to look again at my original trace, taken from the spec sheet. My peak is an order of magnitude higher than spec. That's a problem. Interestingly, the simmed output does not have an order of magnitude issue. Still haven't resolved why the "simmed" file is not an order of magnitude high as well. This might just be sloppy work on my part.

Woofer x-over: Your ckt is more elegant and simpler, and with a higher order slope. What is the process for incorporating BSC into the a standard order configuration, as opposed to a separate ckt as I did? Otherwise, both outputs have a small rise at 1kHz and the similar overall shape. One last question, what do you mean by "woofer delay = 0.6 inches?" I would have expected any delay to be applied to the tweeter.

Thank you for taking the time to put this together. I feel as though I am gaining new insights already and haven't even delved into the tweeter section or W/T integration.
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Old 15th July 2017, 08:01 PM   #12
Lojzek is offline Lojzek  Croatia
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Hi Ed, since we are not designing any filters in the woofer tuning frequencies range, then it doesn't matter what these peaks look like. Our filter works in the kHz region and that's why the impedance curve in that should be realistic.


Beside SPL Copy, there is another particularly quick one that you will find at fprawn labs called FPGraphTracer. Demands the photos to be clear around curves so it locks precisely at once.


BSC is a procedure of creating the response curve that you make in the Baffle Diffraction Response Model module of RM, which you have already succesfully aplied when defining baffle measures and saving this response to the traced FR from manufacturer 2pi measurement.


I guess you wonder about using a separate LR filter additionaly to the LP filter. In general it doesn't matter how you manage to shape the curve of the frd file to create a final and normally looking low passed one, whether it's your way or anyone elses way, it depends what you want to achieve. Usually simple LP filters with larger values inductors are capable enough to make it work, but sometimes it has to be complicated and then your way will work better.


By 0.6" woofer delay, we mean to instruct the program to look at the woofer being 0.6" farther away from the tweeter, assuming our point of view (microphone position) is that tweeter and woofer are in front of us, on a flat baffle (not slanted). This is the standard convention when software adds additional phase delay (in degrees) to the woofer.
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Old 16th July 2017, 07:35 PM   #13
bungelow_ed is offline bungelow_ed  United States
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Yes, I see your point with respect to woofer impedance. Still my goal is to be as accurate in my work as possible.

FPGraph sounds like a program I want to check out. Seems SPLTrace has a hard time with Scanspeak graphs. Especially the older ones. For that matter any that do not have solid lines.

I like the simplicity of having the BSC incorporated into the LP, fewer components -> potentially lower cost. After ask the question I spent hours on the internet looking for the answer. Couldn't find anything that directly answered my question, though I came to the same conclusion as your explanation. Shape the response by adding inductance until a satisfactory result is achieved.

While contemplating the "0.6" question I realized that I was looking at this backward. I should have been looking at the woofer set-back on a vertical baffle. Instead my perspective was how much do I have to tilt the baffle back to align the tweeter.

My plan is to redo the FRD/ZMA files, and have new x-overs done next week. If you don't mind I'll shoot you the files so you can decide whether I gained the insight you shared. Regards, Ed
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Old 16th July 2017, 07:41 PM   #14
Lojzek is offline Lojzek  Croatia
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