I appreciate your reviews Shady. It is great to have advanced warning. That gives me time to figure out the problems. It is a great game I like to play. I have to say I'm pleased with my scorecard on this one.
The first point I would make is that making a curved enclosure like that, with the drivers' center's aligned does not time align the speaker. It does not even make a close time alignment.
So let's take this 140 Hz LF/MF cross over. It is a second order 12 db. per octave crossover, so the phase shift at crossover is 180 degrees.
So a half cycle at 140 Hz is 4'. 3.9' to be more exact. So the fancy cabinet does not time align the drivers.
This low crossover as you point out creates a problem in that the caps and inductors are huge. The inductor in series with the woofers, will have a significant enough DC resistance to adversely affect performance. I know this, as I did extensive research on this forty or so years ago. I came to the conclusion that if you want high performance with a crossover that low, then an active design is absolutely mandatory. In addition you end up with an adverse load to the amp, far more likely than not, as is the case here. This I predicted. Yes, this matters. These days it is not necessary as I'm pretty certain a class D amp and active crossover could be provided for the same cost as those expensive inductors and caps. What is more digital technology can truly time align the drivers.
The next problem that was created was those rear firing woofers. This was done to keep the cabinet narrow and still provide enough power to forgo a sub. So that system is equivalent to a 12" driver in each speaker.
However we now have the thorny problem of baffle step compensation. So in a front driver arrangement there is a transition between a mono pole speaker and an omni pole speaker, known as the transition frequency. This is compensated for by boosting 6 db per octave below the transition frequency.
However we now have rear facing drivers coming in below the transition frequency. You can see from the FR that the BSC is initially under compensated and then over compensated below the 140 Hz crossover. In addition the mid range drivers are going to be operating below the transition frequency. This probably accounts for the fact that this mids are not good mids, and can not handle the speech discrimination band.
This leaves a small cone woofer certainly operating close to its resonant frequency, which I don't like. Also as you point out, it makes it a prime candidate for voice coil burnout if driven hard.
I regard your measurements and recordings of that crossover situation as suboptimal as I suspected. I would bet that on prolonged listening that alone would not make me happy.
So, I do consider this an unhappy design concept. At least a semi-active approach would have been far better, and also allowed for much easier insertion of the LFE signal. it would have been a much better fit to current AVR and AVP practice.
That impedance drop to just above 2 ohms is going to stress a lot of amps and almost certainly cause premature failure of even some pretty robust amps. I would personally not like drive those with one of my 909s, which are about as robust as they come. I think that a lot of amp failures are actually down to the speaker designer and not the amp designer. I personally take this facet of speaker design extremely seriously and giving the issue as wide a berth as I can.
In many ways these speakers do have similar design objectives to my main speakers, but I solved the issues very differently. I made the decision to go for an active/passive design. This allowed for easy integration of sub and LFE signals. It allowed for the baffle step issue to be entirely solved and adjusted for room boundaries on an infinitely adjustable basis.
Now these speakers are much less costly than mine, even with DIY. So it is not entirely apples to apples. However if you factor in longevity then over time mine become a very good deal.