I started out as a complete died in the wool headphone nut, Speakers were for "parties" as I saw it.
Later, I came in touch with Cain and Cain, started an apprenticeship, and in many ways never came back from single drivers.
I am now in Japan devoting my life to studying the things!
So yes, speakers indeed do have HiFi applications, and a certain allure, and generally, I think that they are preferable, though I continue to keep one foot on each side of the line. I love headphones still and will never give up on them.
This is for many reasons: to get headphone resolution out of speakers (esp multidrivers) is an incredibly expensive undertaking. Headphones physically posess specific advantages:
I think of it this way: headphones are like a motorcycle. Cheap for the zero to 60. Very fast in a straight line, incredibly exciting to drive, but cannot enjoy that speed easily with two people. also, it is generally hard to ride them long distances.
Speakers are like a car. Maybe a bit slower on average, but the sports models have better handling than a motorbike, and some cars do not loose too much on the acceleration category. Of course, nothing can compare with a formula one car.... that is the kind of company I like to keep!
I must say though, that some of the headphone "super systems" are simply without peer in all the audio world.
I think that the happy world of the middle lies in single drivers loudspeakers, electrostat ear-speakers, and some electrostat loudspeakers. Fully front loaded horn systems can be very nice too, but can get VERY expensive. Single drivers can get darned cheap for their performance level. More of the money you spend tends to go towards the driver unit itself, not the complicated crossover, high power amps, etc.
Microphones, 99% of headphones, boomboxes, most car audio: all single transducer. Most studio monitor speaker systems? not single driver (though there are some...). Most studio monitor systems tend to be highly specialized applications of multiple drivers, which do work well, IMO, when compared to most consumer grade, and frequently underengineered multi driver systems.
Even then, I think it is important to not be too much of a snob to forget to simply listen to and enjoy the music through whatever happens to be playing it, even through cheap headphones layed down playing on the coffee table in order to try to entertain more people. Music is music. My audio hobby, the climbing of the mountain, simply was not fun for me until I learned to detach myself somewhat from my critical nature except when I need to use it.
Of course, I have built single driver speakers for a living for quite some time now, so I guess that all my opinions must be weighed against that fact. So please, understand that I am disclaiming myself fully. While I am indeed a manufacturer, I really consider myself to be simply a "pro-sumer." So I reserve the right to have an opinion, and to love audio like all the rest of you...
Regarding my opinions of single drivers vs. multidrivers, please understand that I am devoting my life to simply building what I love rather than trying to "trash" an entire category of speaker design.
So please, all this is IMO,
-Clark