I have only seen on-axis measurement and a waterfall of the DD67000. But there's much we can know based on physics and knowledge about speaker design.
Here's the on-axis measurement measured by Hifi News:
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The uneven response in the highs is as expected. When you have two vertical drivers with this much spacing and a crossover at 20 kHz, the result is polar lobing and comb filtering. That's unavoidable.
The horn is very short in regards to directivity control. Result is that it will only provide a constant vertical directivity in a small frequency area. Horizontally I don't how well the horn measures off-axis. It would be interesting to see. Crossing from a horn over to a front firing at 850 Hz isn't trivial. Front firing woofers are omni in the lows and than gradually narrows at higher frequencies.
30 Hz:
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331 Hz:
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Above approximately 400- 500 Hz, the woofers will exhibit polar lobing and which get's worse the higher you go up.
501 Hz:
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840 Hz:
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But I think the main problem is the lack of a uniform directivity from front firing woofers.
I haven't experienced much with dual 15" woofers next to each other, but I've worked quite a bit with crossing a large horn to a single 15" front firing woofer and which should be similar considering the 2.5 design. I've used a steep crossover at 600 Hz which makes it easier. But it's challenging because you are going from a horn with constant directivity to a woofer that isn't constant. The woofer is therefore much more colored in the response from the room. Crossing over to a midbass horn with similar directivity is far more seamless and yields a much more even response. The drawback here is size.
BTW. We can see how the horizontal polar of 15" will be similar to, by looking at the vertical polar of the JBL 4638.
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Whilst such off-axis measurements are limited compared to a polar shown as sonocrame, we can still cleary see some issues here. Edit: This will be different with a crossover to a single 15".
When the speaker is passive with no signal aligment, that means the sound from the different drivers are not reaching the ear at the same time. Personally I find that's a highly audible drawback.
The impulse response from the previous DD66000 model is here:
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As a side note. It's sad how difficult it is these days to get proper measurements from the speaker brands. I highly doubt JBL would be willing to share proper polars. Quite the contrast to the past when i.e. Don Keele worked there and showed everything. He drew everything by hand by the way.