I think I know the charms and the risks of seconding the symmetry temptations well. We audiophiles, as a rule, are prone to a special kind of synesthesia, stone and glass under the gear make the sound bright, wood makes it smooth, silver wires are clearer than copper and so on.
When I have done changes to mainly second a visual necessity the results have always been modest and not up to expectations. On the other hand, what you see is what you get, as in older Microsoft Word… In the end, though, what you hear is what you hear and sonic truth sooner or later digs its way to awareness.
They demonstrate the benefit of direct drive with no crossover components between power amp and driver, and no interaction of overlapping signals from multiple non-coincident drivers, however they also have their limitations arising from the one diaphragm having to handle signals from low bass to high treble, my understanding being that many, if not all, designs have limited limit low end capability and/or limited output level.
It goes without saying that for active system to work effectively the crossover needs to be good. In particular they must cross over at appropriate frequencies and with appropriate cutoff slopes (simplest, with a speaker that is well designed in the first place, is to have these the same as the original passive XO), and the phase as well as level must be matched between drivers. Some active crossovers facilitate easy tailoring of some or all parameters by the user, which can be done in-room with software like REW monitoring the effect, thereby tuning to the best achievable in a the listener’s room.
You pick your poison with any design. The strengths you quoted would be the drawbacks stated for a multi driver based design. As for the real drawbacks, Low frequency output is largely resolved on modern designs with exotic large full range drivers. They cost a lot, but then you aren’t putting money into other drivers or the crossover. Many overcome output limitations using horn loading. My Omegas manage with 98db sensitivity using a large reflex ported cabinet and full range 8" drivers to provide realist output in a realistic compact enclosure.
From user experience, the biggest drawback of a single driver seems to be off axis response and reliance on a listening position. Coming from a 250DR driving floor standing PMCs, to a 10w tube amp driving Omegas, no, there isn’t as much bass. But it isn’t exactly bass light either (rolling off at 38Hz) and they are in a large room. They have no problem reaching the SPL levels my PMCs did - I’ve measured.
The increased transparency on them, even with lower end amplification and source compared to the Naim/PMC setup is very apparent. Certainly, if someone craves the transparency of an active system but the cost and box count is prohibitive, I’d thoroughly encourage them to try a crossoverless speaker. Some even do use multiple drivers for hi and low frequency that just just happen to compliment each other’s rolloffs and be safely tolerant to frequencies outside of their response range (thinking of Zu speakers here). But the linearity of a single well behaved driver is quite beguiling. I wouldn’t knock it unless you’ve tried it (recently).
I do use subwoofers to augment each channel, these are run via a 10x10 mini dsp with separate linear PS and a few internal upgrades to minimise the drawback of A>D and D>A which only affects the subs. I follow a Harman curve and time align and EQ subs only
I might at some stage try active but it’s a long way down my list. More tempting to explore that with the centre channel as I have a spare 135 that could be used for biamping the centre (not able to passively Biamp)
Re full range speakers, ever since I first got interested in hifi I have I had a soft spot for Lowther, both their full range drivers, and their speakers built with them, though not giving what I want (albeit not heard for many years). And I have been aware of Fostex, a significant player in the full range arena, especially the DIY market, though at least last time I looked into them (a decade or two ago now) they weren’t really at the top of the game. And now there is a German brand, Voxativ, with highly developed drivers that fascinate me, seemingly developed further from the Lowther approach: Reviews of one of their speakers have been very good. I haven’t heard them myself, but I am guessing the bass end may be a tad lacking for my taste. However, interestingly, one of their drivers has been used in the Ferguson Hill FH001 transparent horn, a product I would love to hear, but used only down to 150Hz.
I finally try biamping my XS2 with NAP100 tonight, driving my ATC scm7 bookshelve! The result is marvelous! It has more depth, better texture, details and most importantly, much more natural & musical!
But in the combination of, nap100 for bass unit & XS2 for the tweeter. This would perform much better in the reversed position in my opinion!
This answer hints at but doesn’t explicitly explain the derivation of terms active and passive: A passive crossover contains only passive components (such as resistors and capacitors) to create an electrical filter network, whereas an active crossover also contains active components (such as transistors) to create an electronic filtering network.