Well, I was taught a couple of simple ways of looking at speakers design,1 way,or 10 way. The ways actually do not seem to matter. If you are building a speakers and only have a marginal woofer and a marginal tweeter to work with, you may well need a marginal midrange driver to at least make the sound tolerable. If you use a very good woofer and a very good tweeter, you made not need
midrange as your drivers blend well to cover that important midrange area, If you are out in out trying to build the very best full range loudspeaker you can, you may well build a three way as you are able to compromise with the woofer/midrange drivers in that your woofer can be used to reproduce the lower frequencies it was really(on average) more designed to do. I think a lot of woofers in 2 way monitors are more midbass drivers, and there must be something there because I see a lot of subs being sold. I just had a pair of SR12 Silverline's, and where it may be the best bass I have ever heard in a monitor that size, I genuinely would not call it soul satisfying bass. IMHO, seems like a lot of high dollar(and unlike many in this group, I consider $1k high dollar) 2 way monitors are really unfinished 3 ways, waiting for a woofer. None of the rules are solid, I do think a lot of it has to do with parts on hand, how much money is being allowed for R&D(usually little)marketing(usually more) exotic veneers(makes a wonderful sonic difference on a 12 inch tall cabinet, doesn't it?) and actual production costs. There are some great 2 ways
Thiel, Fusalier, Silverline, Spica, Rogers, etc, just as there are some great 3 ways, Vandersteen, KEF,PSB's Utopia
etc. I really do think it has as much to do with what you have ready to use when you are designing a speaker to a specific price point in the market, especially a price point you need to be in quickly because profits are looming there. Nothing wrong with that, its business and none of these people would be in it if it was not tied to making money doing something you like doing. And I think they are pretty lucky to be doing that.
midrange as your drivers blend well to cover that important midrange area, If you are out in out trying to build the very best full range loudspeaker you can, you may well build a three way as you are able to compromise with the woofer/midrange drivers in that your woofer can be used to reproduce the lower frequencies it was really(on average) more designed to do. I think a lot of woofers in 2 way monitors are more midbass drivers, and there must be something there because I see a lot of subs being sold. I just had a pair of SR12 Silverline's, and where it may be the best bass I have ever heard in a monitor that size, I genuinely would not call it soul satisfying bass. IMHO, seems like a lot of high dollar(and unlike many in this group, I consider $1k high dollar) 2 way monitors are really unfinished 3 ways, waiting for a woofer. None of the rules are solid, I do think a lot of it has to do with parts on hand, how much money is being allowed for R&D(usually little)marketing(usually more) exotic veneers(makes a wonderful sonic difference on a 12 inch tall cabinet, doesn't it?) and actual production costs. There are some great 2 ways
Thiel, Fusalier, Silverline, Spica, Rogers, etc, just as there are some great 3 ways, Vandersteen, KEF,PSB's Utopia
etc. I really do think it has as much to do with what you have ready to use when you are designing a speaker to a specific price point in the market, especially a price point you need to be in quickly because profits are looming there. Nothing wrong with that, its business and none of these people would be in it if it was not tied to making money doing something you like doing. And I think they are pretty lucky to be doing that.