If tweeters are better suited to highs, small speakers to mids and large woofers to bass, why don’t we have an array of ten say ten or twenty gradually increasing speakers from tiny tweets to ENORMOUS woofers, each with a unique crossover at a specific frequency they perform best at?
We really seem to have settled on three sizes. Tweets, miss, and subs. Why is that the case?
Surely more speakers handling less varied frequencies means a better response, right?
It’s matter of cost, and compromise. Crossovers are not infinitely steep, so there will be multiple drivers playing the same signal, resulting in interference in the dispersion pattern. That interference pattern is undesirable, as it creates directivity issues on the speaker, and this is why drivers that play the same signal are placed vertically close together, as this makes them merge better and points the crossover null lobes up and down rather than sideways, where they might point to someone’s listening spot. So your hypothetical speaker would be very tall, most likely, and come with lots of directional lobing.
2-way is the smallest it can get, but it is somewhat a compromise in harmonic distortion at midrange, or the bass extension, depending on how large the woofer is. 3-way is likely the sweet spot, the smallest design that realize both low harmonic distortion and extended bass response, in my opinion. If midrange and tweeter are coaxial, that is close to ideal, e.g. see Kali IN-8, various KEF designs, or Genelec The Ones series. Then, 4-way and 5-way may be good if you need absolutely the full bass range down to sub-20 Hz, or very high SPL, or something, but I doubt that kind of design matters all that much for home use.
I have 10" woofer and 1" metal dome tweeter on my living room’s speaker system, thus it is a 2-way. The large woofer gives in-room F3 bass to around 25 Hz, though the woofer and tweeter are placed quite far apart, and thus the crossover lobes are sizable and start near the acoustic axis, and thus you can’t allow much vertical displacement from the acoustic axis if you want to enjoy flat on-axis response. Therefore, longer distance is ideal. From measuring it, I can plainly see that the woofer is struggling to keep harmonic distortion below about -50 dB, until the crossover happens at about 2 kHz. As soon as it crosses over to the tweeter, harmonic distortion drops below the room’s noise floor.