The Defiants - InDIYana 2019 Build

[jhollander]

If you are using as measured phase you do not need offsets or the T+W frd

[KEtheredge87]

If you are using as measured phase you do not need offsets or the T+W frd

Thanks John,

What I think you just told me was that I am unwittingly screwing myself up by applying a z-offset, measurement distance, and X/Y woofer offset in PCD. I should just take my Blended near/far woofer response and my farfield tweeter response and design from there.

I still need my in-box ZMA measurements, right?

Do I understand you correctly? (You'd think I'd have this down pat by now... especially for the number of times you've helped me on it!)

[jhollander]

Whoa, if you are using a blended woofer file the phase is not accurate and you are not using "as measured" phase. You are back to extracting minimum phase for the woofer blended file, then the tweeter, and finding the offsets. Once you extract minimum phase for the woofer you need to do that for the tweeter as well. You can't mix minimum phase with as measured phase files.

Sounds like you may have not extracted min phase for the tweeter file.

Also note that if you changed the measurement distance between your simulation measurements and your "with crossover" measurements the null will not be the same.

[rpb]

Here's what you can do. Move the mic up about ten or fifteen degrees, and see if the null gets deeper. Then, if not, move it downward about ten or fifteen degrees, and check again. This will tell you if the tweeter is ahead or behind. Tweak the filters for a deeper null on axis, then switch back the polarity, and audition. If neither is deeper, then you may be off a lot. In that case, you may need an additional x-over part, or one less.

[rpb]

Can you show us a measurement of the woofer and tweeter (with filters) individually on the same graph? The shape of the roll-offs can tell you a lot.
I like the shape of your tweeter roll-off. Nice and gradual. If the woofer has more of a knee, that may not tend to have as deep of a null, when matched with the smooth tweeter roll-off.

[KEtheredge87]

Thanks jhollander and rpb . Neither of you have said anything that came off negatively, so I'm just being goofy with this meme below... I remember John's lessons now. I'll go back and take proper measurements, run them through the blender and extract minimum phase for both woofer and tweeter, and give this another whirl! Thanks for jogging my memory!

[rpb]

In theory, you would want a deep reverse null at 1.5 to 2 meters on the tweeter axis. That might not be the same null you get measuring at less than 1m. It's just the geometry changing the distances from the mic, to each driver.

[KEtheredge87]

OK... I think I did a better job of measuring my drivers and preparing for XO design. Basic steps were:

1) Measure nearfield woofer, and farfield tweeter, farfield woofer, and farfield woofer + tweeter
2) load woofer nearfield and farfield into blender, apply baffle diffraction, blend appropriately, extract minimum phase and export FRD
- I picked 0.75" radius... but I don't know how that translates to a variable length facet cut.
3) load tweeter farfield into blender, apply baffle diffraction (again with 0.75" radius), extract minimum phase and export FRD
4) load minimum phase FRDs into PCD7, apply overlay of woofer + tweeter farfield curve
5) set measurement distances and offsets in PCD, determine Z-offset.

As it happens... PCD said my z-offset was literally 0.000mm

Even after doing all that over, something still wasn't quite right, but I kinda lucked out and arrived at a solution. A pretty darn good looking solution in fact! Both Xsim and PCD are telling me my tweeter needs more padding, and that my reverse null isn't quite as sharp as the OmniMic is telling me... but this sounds really nice so far I tend to give speakers the "smile on my face" test... which is to say I tweak until I can't help but smile and think "Man that sounds good!"... and I'm smiling right now

Assuming I make no changes to this, I think the only component robustness issue might be R2 in my tweeter... if I really wallop these guys with 100W of 4 kHz energy, XSim says that resistor will be dissipating over 50W of power. That dissipation result sounds a bit excessive to me, but I don't have any other way to estimate that currently.

In the photos below, the Omnimic traces without reverse null have 1/6 octave smoothing applied. I did this because I read Jeff Bagby's whitepaper that states the human brain interprets frequency differences on a 1/6 octave smoothing level anyway, so that's a decent approximation for how flat I think it is by listening.

Time for some sleep!

[Wolf]

Looking good to me!

I started my cabinets tonight, so I'm at least moving...
Wolf

[PWR RYD]

Keith,
In your steps 2 and 3 you state that you loaded the far field driver measurements then applied baffle diffraction. Your far field measurements already contain all the diffraction effects (assuming your measurement distance is at least two times the baffle's width). Are you adding something more to your already "good" measurements which is making them "bad"?

The only thing I use the blender for is to "blend" the near field and far field for the woofer, and add upper and lower tails to both drivers to extend the phase response to 10 Hz and 40kHz, and to remove the room's response/noise floor from the tweeter's bottom end response. Then of course extract minimum phase for each driver.

[jhollander]

Item 3 is not required, other than extracting minimum phase. Your tweeter far field measurement has the baffle in it. If you do load the the tweeter to the blender, just the trim measured tail by adjusting the LF tail, then extract minimum phase.

[jhollander]

cross post...great minds think the same?

[wogg]

Whoa, if you are using a blended woofer file the phase is not accurate and you are not using "as measured" phase. You are back to extracting minimum phase for the woofer blended file, then the tweeter, and finding the offsets. Once you extract minimum phase for the woofer you need to do that for the tweeter as well. You can't mix minimum phase with as measured phase files.

Sounds like you may have not extracted min phase for the tweeter file.

Also note that if you changed the measurement distance between your simulation measurements and your "with crossover" measurements the null will not be the same.

This inadvertently really helped me out. I was stuck on using unmodified as measured files to align offsets which was throwing me off trying to get the close mic blended response to work. With this little nugget of information, I created a blended min phase response for the woofer, then just applied min phase to the tweeter and combined responses to pull into PCD.

Thanks John!

[wogg]

OK... I think I did a better job of measuring my drivers and preparing for XO design. Basic steps were:

1) Measure nearfield woofer, and farfield tweeter, farfield woofer, and farfield woofer + tweeter
2) load woofer nearfield and farfield into blender, apply baffle diffraction, blend appropriately, extract minimum phase and export FRD
- I picked 0.75" radius... but I don't know how that translates to a variable length facet cut.
3) load tweeter farfield into blender, apply baffle diffraction (again with 0.75" radius), extract minimum phase and export FRD
4) load minimum phase FRDs into PCD7, apply overlay of woofer + tweeter farfield curve
5) set measurement distances and offsets in PCD, determine Z-offset.

As it happens... PCD said my z-offset was literally 0.000mm

Even after doing all that over, something still wasn't quite right, but I kinda lucked out and arrived at a solution. A pretty darn good looking solution in fact! Both Xsim and PCD are telling me my tweeter needs more padding, and that my reverse null isn't quite as sharp as the OmniMic is telling me... but this sounds really nice so far I tend to give speakers the "smile on my face" test... which is to say I tweak until I can't help but smile and think "Man that sounds good!"... and I'm smiling right now

Assuming I make no changes to this, I think the only component robustness issue might be R2 in my tweeter... if I really wallop these guys with 100W of 4 kHz energy, XSim says that resistor will be dissipating over 50W of power. That dissipation result sounds a bit excessive to me, but I don't have any other way to estimate that currently.

In the photos below, the Omnimic traces without reverse null have 1/6 octave smoothing applied. I did this because I read Jeff Bagby's whitepaper that states the human brain interprets frequency differences on a 1/6 octave smoothing level anyway, so that's a decent approximation for how flat I think it is by listening.

Time for some sleep!

I'm not sure you need to apply simulated baffle when you measured in far field in your step 2... but the smile test doesn't lie. These will be fun to hear!

[Mountainman Bob]

I'm not sure you need to apply simulated baffle when you measured in far field in your step 2... but the smile test doesn't lie. These will be fun to hear!

Listening, hearing......what novel ideas!