The minimum phase suggests acoustic crossover is near optimal for DE250...would you agree?
It's durn close, I would say, yes.
How did you determine the acoustic center to be 3" below waveguide? Doesn't on axis with tweeter look better?
As found previously, as I recall, it's 3" below the waveguide center, i.e., the tweeter axis, thus still within the waveguide.
To find that, I inverted the polarity of the HF driver and moved the mic up and down to find the location of the deepest notch. 1/8" either side of that height, and it is not so deep. Note also I switched to "unsmoothed" to dial it in precisely (Orange).
At that point, having smacked myself in the head for not doing this first so that all of the measurements would have been done there, I reversed the HF connection and took a new measurement (Violet). You can see that it is nearly identical to the previous one, next graph above. There is somewhat better summation with the woofer just below crossover being one difference, but not enough to warrant doing everything over.
At that point, I clicked the minimum phase button and saw that it was good. Those determinations were made with D220Ti, BTW. Should I go back and do the same with DE250? Yeah, but it'd be more worthwhile moving on with both woofer and waveguide mounted on the same baffle in some fixed alignment.
These measurements confirm Jack's findings that inverting the polarity of the compression driver in large part compensates for the horizontal displacement of the driver acoustic centers when using the deeper QSC waveguide. Do I know where they actually are yet? Only by inference....
What is the acoustic center angle for a baffle-mounted "standard" large Advent EWG (WG cut-out incorporating the tweeter opening) ? Curious about correction by bringing the WG forward on a baffle step-out insert and also bringing the WG ajacent to the woofer.
Don't know, but I'm setting up the WIRED Advents this afternoon for a demo, and will make a point of finding out.
Addl; has anyone tried the 6X6 JBL on a large advent EWG? If so, what was the ACA?
I don't believe anybody's done large Advent with the 6" square waveguide, which is quite shallow, implying that the horizontal offset of acoustic centers would be different. Would I suggest the HF might even be ahead of the woofer when mounted on the same plane? Not without measuring to find out.
My own pair are OLA chamfered with the 8" square JBL waveguide, which is deeper than the eWave standard PT. It would be interesting to compare; with its constricted flare, I can't begin to guess where the acoustic center might be. In both of these cases, the large Advents are originals, with wider C/C distances than news. Plenty of news around here, as well, but I may be doing something else with those. I consider smaller, shallower systems like AR4x, BA60, KLH24, etc. more appropriate platforms for the 6" square PT, which we all apparently agree is an excellent performer.... :yes:
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