Ah, but a key here is the example is a small cabinet... and this technique could have merit, but let's think about how to investigate it?
I think it would be a good idea to refer folks back to this PuriFi blog article about the SPK16 project, which got my attention partly because of how it refers to using tools I'm familiar with from my old day job, but also one of the few documented cases I've seen of internal pressure zone measurements.
An internal pressure zone measurement is obtained by having a hole drilled though the enclosure wall of a diameter suitable for a chosen measurement test microphone. This microphone needs to be well optimized for high SPL, and the test done at fairly low external SPL I'd imagine, also. For this small cabinet SPK16 cabinet, it is thought to be valid for acoustical output below about 100Hz, as it should be free of standing waves and similar artifacts that also impact the driver output.
While this looks more like a simulation, that is due to the absence of any room reflections or interactions with the measurement.
This discussion is forcing me to "tip my hand" because I bought another microphone last fall just for the purpose of doing this kind of measurement (though I've also considered using the Pocket CLIO setup, reviewing it reveals SPL processing issues that might be a limitation).
So, yeah, doing this for both the original big box approach and for these new cabinets is on the project agenda, but for doing the more complete comparison I wanted, I needed to have the POC V3 cabinets built and some testing done.
So, would something like the internal absorption/diffusion panels Steve drew up work? And for a large cabinet would it just add an acoustical network in series with the PRs? Ultimately, I figure I should be searching for the simplest to implement solution...
Now, just to toss another tidbit into the discussion, I have some Excel files for designing line arrays which also include some basic calculations for how a stacked series of drivers impacts the overall frequency response, due to off axis interaction at higher frequencies. Of course, that has implications for even low frequency short line arrays, and you can see that to a limited degree in my plots above for just two drivers.
Lots more stuff to investigate with time, but my immediate focus is for useful results... for this system design build. It's taken a long time just to get to the point.
But then, consider the Kurosawa- cabinets still in storage, all the drivers on hand, and parts for a preliminary crossover design. I didn't just dive back into it because the parts cost is now so outrageous that it would have limited applicability for HTG members, in all likelihood. And at this point I would update the midrange and tweeter... for performance reasons, from the original Accuton and ScanSpeak parts. Recall that this system incorporates internal baffles separating each low frequency woofer and PR combo, to eliminate vertical standing waves.
Some day...
unk:
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