Do we really need anything more than 8" woofer and 1" tweeter for medium size room?
I once owned a pair of S.P. Technology Timepiece 3.0’s - lovely speakers. It featured a low fs 8" Seas woofer/mid and a 8-10" waveguide loaded 1" tweeter from SB acoustics, crossed over at about 800Hz. I’d never heard a sole 8" woofer per channel load a mid-large sized room with clean, deep bass down to (or even below) 30Hz as implemented here. The problem with my specific listening environment was that they simply overpowered the room in the central to lower bass, something that could have been dealt with more effectively than I ended up doing, but I also found they lacked the proper energy and snap in the upper bass/lower mids - perhaps co-influenced by the problems in the bass region (the solution turned out to be seeking speakers that housed bigger bass/mid drivers, at the cost of lower bass extension - more on that later).
The stand-out sonic feature of the Timepiece’s, as I heard it, was their waveguide loaded tweeter. For some years I’ve avoided direct radiating tweeters, because I find they sound more like small and strained domes rather than the instruments they should be emulating with a sense of ease. The waveguide de-stresses the dome tweeter of the Timepieces, making it perform with significantly lower distortion, and ends up multiplying its effective radiation area equivalent approximately to that of the mouth area of the waveguide (close to 10"). The high frequencies here didn’t sound like a tweeter, but like an extension of the frequencies below it with actual substance and a wonderful sense of fullness and dynamics; it sounded rather live. So, is a sole 1" direct radiating dome tweeter enough? No, if you ask me - certainly not unassisted.
To alleviate the problems in the bass region (to some extent by virtue of absence), and more significantly those of the upper bass/lower mids, I have ended up preferring a larger sized unit here - at first 12," and currently a hornloaded 15" driver. Not every 12" or 15" driver would do - certainly not those long-throw, heavy weight, polypropylene-like diaphragm and low fs units - but that’s another story unto itself.
To me larger paper coned bass/mid drivers simply offer a more realistic, full and relaxed tone compared to smaller, non-paper coned units, but typically they don’t do this without a sacrifice: lack of low bass extension. A light paper coned 12" or even a 15" bass/mid driver that doesn’t delve much below 40Hz may sound "smaller" in a sense compared to a deep-diving 8" hi-fi driver, but they generally offer something very else in terms of tone and naturalness. For true low-bass extension a subwoofer would be called for with this type of larger diameter drivers.
Whether an 8" driver would be "enough" in a mid-sized room depends on the specific nature of the question. 8" drivers can go low, but where they do and act as mids seem to sacrifice the latter, and that goes for even smaller (or bigger drivers) drivers as well. A higher fs 8" may deliver fine mids, but I suspect would come up short in the upper bass region. The aim for more radiation area, higher sensitivity and how the coupling to the air is achieved is, unless we’re dealing with pro use, not so much, if really at all about max. SPL or punch-in-the-chest abilities as it has to do with ease of presentation and overall naturalness. Pushing a limited radiation area rather violently (and using more effort), or a bigger ditto more gently - I believe it to be of significant importance, just as radiation area in itself is.
